How to match pattern in bash?
Suppose that I have a variable $x, I want to test if the content of $x match the pattern 'abc*'. If yes, then do something. (The operator == doesn't match patterns, if I understand it correctly.) Is there such a build-in feature in bash? Or I have to rely on some external program such as perl to test the pattern matching? -- Regards, Peng
pushd, popd and dirs of different bash processes communicate by an external file
Hi, I'm wondering if there is a way that different bash processes share the same stack. One way of doing so is to use a file to save the stack. It is not difficult to implement this function myself, but I'm just wondering if there is any simpler solution or anybody has done it already. Thanks! -- Regards, Peng
How to match regex in bash? (any character)
Hi, I know that I should use =~ to match regex (bash version 4). However, the man page is not very clear. I don't find how to match (matching any single character). For example, the following regex doesn't match txt. Does anybody know how to match any character (should be '.' in perl) in bash. [[ "$1" =~ "xxx.txt" ]] -- Regards, Peng
Re: How to match regex in bash? (any character)
On Mon, Sep 26, 2011 at 9:49 PM, John Reiser wrote: > Peng Yu wrote: >> I know that I should use =~ to match regex (bash version 4). >> >> However, the man page is not very clear. I don't find how to match >> (matching any single character). For example, the following regex >> doesn't match txt. Does anybody know how to match any character >> (should be '.' in perl) in bash. >> >> [[ "$1" =~ "xxx.txt" ]] > > The manual page for bash says that the rules of regex(3) apply: > > An additional binary operator, =~, is available, with the > same > precedence as == and !=. When it is used, the string to the > right > of the operator is considered an extended regular expression > and > matched accordingly (as in regex(3)). The return value is 0 if > the > string matches the pattern, and 1 otherwise. > and also: > Any part of the pattern may be quoted to force it to be matched > as a > string. > > Thus in the expression [[ "$1" =~ "xxx.txt" ]] the fact that the pattern > is quoted [here the whole pattern appears within double quotes] has turned the > dot '.' into a plain literal character, instead of a meta-character which > matches > any single character. > > The usual method of avoiding quotes in the pattern is to omit them: > [[ $1 =~ xxx.txt ]] # the dot '.' in the pattern is a > meta-character > or to use a variable: > pattern="xxx.txt" # a 7-character string > [[ $1 =~ $pattern ]] # the dot '.' in $pattern is a > meta-character > Example: using all literals in an instance of bash: > $ [[ txt =~ xxx.txt ]] && echo true > true > $ > > Also notice that quotes are not needed around the left-hand side $1 : > Word > split‐ > ting and pathname expansion are not performed on the words > between > the [[ and ]] ... > > Thus there is no need to use quotation marks to suppress word splitting > inside double brackets [[ ... ]]. Thanks for the clarifications of all the replies. Now the manual makes much more sense to me. -- Regards, Peng
Re: How to match regex in bash? (any character)
On Tue, Sep 27, 2011 at 6:51 PM, Chet Ramey wrote: > On 9/27/11 6:41 PM, Roger wrote: > >> Correct. After reading the entire Bash Manual page, I didn't see much >> mention >> of documentation resources (of ERE) besides maybe something about egrep from >> Bash's Manual Page or elsewhere on the web. After extensive research for >> regex/regexpr, only found Perl Manual Pages. >> >> Might be worth mentioning a link or good reference for this ERE within the >> Bash >> Manual (Page)? > > The bash man page refers to regex(3). On my BSD (Mac OS X) system, that > refers to re_format(7), which documents the BRE and ERE regular expression > formats. On an Ubuntu box, to choose a representative Linux example, that > refers to regex(7), which contains the same explanation, and the GNU regex > manual. This sort of "chained" man page reference is common. > > If you like info, `info regex' on a Linux box should display both pages. Since regex(7) is actually what should be referred on ubuntu, and there is indeed a manpage regex(3) on ubuntu, the difference on which regex man page should be specify in man bash. I was looking at regex(3) on my ubuntu, which doesn't have any relevant information. Also, adding a few more examples just cost a few extra lines, I don't think that the manpage should be so frugal in terms of adding examples to elucidate important concepts. -- Regards, Peng
Re: How to match regex in bash? (any character)
On Thu, Sep 29, 2011 at 7:22 AM, Greg Wooledge wrote: > On Wed, Sep 28, 2011 at 12:43:01PM -0800, Roger wrote: >> Seems I used 'man regex' as well here. AKA regex(3). But I did >> realize this a few weeks ago; the real regex description being 'man 7 regex'. >> The Bash Manual Page denotes only regex(3). > > You're relatively fortunate that it's *that* easy to find on Linux. On > Linux, regex(3) points directly to regex(7), and you're done. > > On HP-UX, regex(3X) points to regcomp(3C) which points to regexp(5) which > contains the actual definitions. > > On OpenBSD, regex(3) doesn't even *have* a SEE ALSO section; it's a dead > end. And regcomp(3) is the same page as regex(3), so that doesn't help > either. One would have to backtrack entirely, perhaps to grep(1). > However, buried deep in the regex(3) page is a reference to re_format(7) > (not even boldface). And re_format(7) has the definitions, but getting > there takes perseverance. (For the record, grep(1) does point straight > to re_format(7).) > > So you see, bash(1) *cannot* just link directly to regex(7), because > that's not actually the correct final destination on most operating > systems. It's only correct on Linux. Bash uses the regex(3) library > interface, so that is the correct place for bash to refer the reader. Therefore, either bash manpage should specify clearly which regex manpage it should be in each system (which a bad choice, because there can be a large number of systems), or the bash manpage should omit all the non consistent reference and say something like "see more details in info" or something else that is platform independent. Referring to regex(3) without any quantification is not a very good choice . -- Regards, Peng
Re: How to match regex in bash? (any character)
On Thu, Sep 29, 2011 at 10:38 AM, Chet Ramey wrote: > On 9/29/11 9:48 AM, Peng Yu wrote: > >> Therefore, either bash manpage should specify clearly which regex >> manpage it should be in each system (which a bad choice, because there >> can be a large number of systems), or the bash manpage should omit all >> the non consistent reference and say something like "see more details >> in info" or something else that is platform independent. Referring to >> regex(3) without any quantification is not a very good choice . > > Why, exactly? regex(3) is the one thing that's portable across systems, > it happens to describe the interfaces bash uses, and it contains the > appropriate system-specific references. `info' is considerably less > portable and widespread than `man', so a man page reference is the best > choice. We all have discovered that regex(3) is not consistent across all the platform. Why you say it is portable? As I mentioned previously, the best is to add a few examples in man bash. Based on the assumption that you don't want to add an example in man bash, then the next choice to add a reference to info, even though it may not always be available in all the system (but as least it should be downloadable from bash gnu website). -- Regards, Peng
Re: How to match regex in bash? (any character)
On Thu, Sep 29, 2011 at 11:06 AM, Greg Wooledge wrote: > On Thu, Sep 29, 2011 at 10:59:19AM -0500, Peng Yu wrote: >> We all have discovered that regex(3) is not consistent across all the >> platform. Why you say it is portable? > > The three systems I mentioned earlier today all have regex(3). Which > system have you found, which doesn't have it? I think that I misunderstood some of the previous emails. However, on ubuntu, there is regex(3) and regex(7). Based on the context in man bash, regex(7) is more relevant than regex(3), although regex(3) does mention extend regular expression, it is more of a document for the C interface. "When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex(3))" Also, regex(3) does not mention the difference between $x =~ .txt and $x=~ ".txt". I think that the difference should be addressed in man bash. Bottom line, regex(3) is not a good manpage to refer in the above sentence. It is better to think of other alternative rather than trying to justify we should stuck with it. >> As I mentioned previously, the best is to add a few examples in man >> bash. > > I would not object to that, but I can't speak for Chet. > > Another option would be to refer to the POSIX definition of > Extended Regular Expressions as a web site. I wish they had > better URLs, though. The URL I have for it at the moment is > http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04 > -- Regards, Peng
How to automatically load alias from .bashrc in a bash script?
Hi, I want to use some alias in a bash script. But I have to include the following line in the script in order to use the alias defined in ~/.bashrc. Is there a way to automatically load the alias from .bashrc so that I don't have to explicitly include these two lines? shopt -s expand_aliases . ~/.bashrc -- Regards, Peng
Re: How to automatically load alias from .bashrc in a bash script?
On Thu, Oct 27, 2011 at 11:43 AM, Greg Wooledge wrote: > On Thu, Oct 27, 2011 at 04:39:23PM +, Stephane CHAZELAS wrote: >> You mean you'd like every bash script you run on your system to >> automatically source your ~/.bashrc. >> >> That sounds like a very unwise thing to do to me, but that >> could be done with: >> >> export BASH_ENV="$HOME/.bashrc" > > He'd still have to turn on the expand_aliases shell option in each > script, though. Unless he puts it in .bashrc. > > (Might as well hand him enough rope to hang himself.) > > If you want to do things properly, use functions instead of aliases. > They are more powerful and more flexible. Thanks for the input. I have some somecommonname.sh, which may be conflict with other commands. Therefore, I only need to rename them to avoid name conflict. But I'm not using any arguments. I think that creating symbolic link rather than alias probably is a better solution. -- Regards, Peng
bash-completion between do and done
Hi, Current, bash doesn't do command completion between do and done (for loop). I'm wondering if this feature can be added. -- Regards, Peng
What is the best to pass an array with specially characters as command line arguments?
Hi, Suppose that I have a verbatim string " a b c ( a'b | " in bash, and I want to pass them as 6 command line arguments. I have to the following conversion using quoteverb.sed to pass the 6 arguments correctly to echo, which is a little bit cumbersome. I'm wondering if there is any better way to pass the 6 arguments. ~$ cat quoteverb.sed 1s/^\s+//g s/^\s\+//g s/\s\+$//g s/\s\+/\n/g s/'/'\\''/g s/^/'/gm s/$/'/gm s/\n/ /g ~$ cat main.sh #!/usr/bin/env bash verbatim_string=" a b c ( a'b | " args="`echo \"$verbatim_string\" | sed -f quoteverb.sed`" cmd="echo $args" eval "$cmd" ~$ ./main.sh a b c ( a'b | -- Regards, Peng
Re: What is the best to pass an array with specially characters as command line arguments?
Hi Clark,
>> > v=" a b c ( a'b | "
>> > a=( $v )
>> > echo "${a[@]}"
>
> There's a @ char here.
I see. It's my mistake.
But I want to pass the 6 short arguments instead of 1 long argument to
echo. (echo is just an example, it can be any command that accepts
multiple arguments.)
~$ cat ./main1.sh
#!/usr/bin/env bash
#set -o noglob
verbatim_string=" a b c ( a'b | "
args=( $verbatim_string )
#set +o noglob
echo "${args[@]}"
~$ ./main1.sh
a b c ( a'b |
--
Regards,
Peng
Re: What is the best to pass an array with specially characters as command line arguments?
Hi Clark,
> What do you mean by "1 long argument"?
>
> [bash-4.2.10] # cat foo.sh
> v=" a b c ( a'b | "
> set -o noglob
> a=( $v )
> set +o noglob
> for i in "${a[@]}"; do
> echo "$i"
> done
> [bash-4.2.10] # bash foo.sh
> a
> b
> c
> (
> a'b
> |
> [bash-4.2.10] #
I misunderstood the usage of "${args[@]}". I though it returns only
one long argument " a b c ( a'b | ", but it actually expanded to 6
short arguments "a", "b", "c", "(", "a'b" and "|". Thanks for
clarification.
--
Regards,
Peng
Re: What is the best to pass an array with specially characters as command line arguments?
On Mon, Nov 7, 2011 at 8:29 AM, Dennis Williamson
wrote:
> On Mon, Nov 7, 2011 at 7:23 AM, Peng Yu wrote:
>> Hi Clark,
>>
>>> What do you mean by "1 long argument"?
>>>
>>> [bash-4.2.10] # cat foo.sh
>>> v=" a b c ( a'b | "
>>> set -o noglob
>>> a=( $v )
>>> set +o noglob
>>> for i in "${a[@]}"; do
>>> echo "$i"
>>> done
>>> [bash-4.2.10] # bash foo.sh
>>> a
>>> b
>>> c
>>> (
>>> a'b
>>> |
>>> [bash-4.2.10] #
>>
>>
>> I misunderstood the usage of "${args[@]}". I though it returns only
>> one long argument " a b c ( a'b | ", but it actually expanded to 6
>> short arguments "a", "b", "c", "(", "a'b" and "|". Thanks for
>> clarification.
>>
>>
>>
>> --
>> Regards,
>> Peng
>>
>>
>
> If you use "${args[*]}" (with quotes and an asterisk instead of an at
> sign), the result is one long argument. Otherwise, it's split.
Thanks! I didn't notice this difference before.
--
Regards,
Peng
What is the correct way to set up login environment in crontab?
Hi, I need to use cron to run some job. I know that cron only set up very basic environment. I'd like to duplicate my login environment. But some environment variables are still not seen when I set the following crontab entry. Does anybody know how to correctly set up the login enviroment? (The manual describes what files are sourced, but I don't want to manually source these files. I'm looking for a simpler way.) * * * * * /bin/bash -i -l -c '/path/programtorun.sh > /tmp/my.log' -- Regards, Peng
Re: What is the correct way to set up login environment in crontab?
On Wed, Nov 9, 2011 at 7:45 AM, Greg Wooledge wrote: > On Tue, Nov 08, 2011 at 09:46:37PM -0600, Peng Yu wrote: >> I need to use cron to run some job. I know that cron only set up very >> basic environment. I'd like to duplicate my login environment. > > Just source /etc/profile and your ~/.bash_profile or ~/.profile (or > whatever) from the script that your cron job executes. > > Personally I would advise against this. Login environments are for > interactive logins, not cron jobs. So neither -i nor -l is necessary? -- Regards, Peng
Re: What is the correct way to set up login environment in crontab?
On Wed, Nov 9, 2011 at 7:45 AM, Greg Wooledge wrote: > On Tue, Nov 08, 2011 at 09:46:37PM -0600, Peng Yu wrote: >> I need to use cron to run some job. I know that cron only set up very >> basic environment. I'd like to duplicate my login environment. > > Just source /etc/profile and your ~/.bash_profile or ~/.profile (or > whatever) from the script that your cron job executes. > > Personally I would advise against this. Login environments are for > interactive logins, not cron jobs. I sourced my ~/.bashrc, which source some other files. It seems the environment variables defined in these files are not seen with env. Why is so? -- Regards, Peng
Re: What is the correct way to set up login environment in crontab?
On Wed, Nov 9, 2011 at 10:41 AM, Greg Wooledge wrote: > On Wed, Nov 09, 2011 at 10:29:52AM -0600, Peng Yu wrote: >> I sourced my ~/.bashrc, which source some other files. It seems the >> environment variables defined in these files are not seen with env. >> Why is so? > > Without seeing the code? Impossible to say. But you're doing it backwards. > ~/.bashrc should be sourced FROM ~/.bash_profile. A login shell reads > ~/.bash_profile only, so it's the responsibility of ~/.bash_profile to > read ~/.bashrc to set up aliases, functions, shopts, and other ephemeral > shell settings that can't be inherited from the environment. Sorry for the confusion. ~/.bash_profile is not the problem here. I have the following line in /path/programtorun.sh . ~/.bashrc In ~/.bashrc, I have ". ~/bash_some". In ~/.bash_some, I have some variable assignment VAR=blah. However, VAR is not seen in env in /path/programtorun.sh (called from cron). -- Regards, Peng
Customize the command resolution in bash?
Hi, bash by default searchs in paths specified in the environment variable PATH (separated by ":"). I'm not aware if there is any cache mechanism to save the run time (but even so, different terminals still can not see the same cache, hence each terminal has the overhead to create the cache). When there are many files in PATH, it is going to slow down the performance. One simple remedy is to instead search in a file where the abspaths of all the commands are saved (of course, this database file can be generated by using the command 'find' to search for all the directories in $PATH, which process can be scheduled to run periodically using cron). To make this work, I'm wondering if there is an easy way to customize the way that bash resolve a command. -- Regards, Peng
invoke tilde expansion on quoted string
Hi, I know from the document that tilde expansion only works if the string is unquoted (see below) ~$ cd '~/..' -bash: cd: ~/..: No such file or directory ~$ cd ~/.. /Users$ I'm wondering if I already have a string variable, is there a bash native to do tilde expansion on it. var='~/..' cd $var#how to change this line? -- Regards, Peng
Why complete doesn't print anything if it is called in a bash script?
Hi, It is strange to me why complete doesn't print anything when it is called in a bash script. I must have misunderstood some fundamentals. Does anybody know why? Thanks! ~$ cat main.sh #!/usr/bin/env bash . ~/.bashrc complete ~$ ./main.sh ~$ complete |head complete -F _kill kill complete -F _renice renice complete -F _smbpasswd smbpasswd complete -F _postconf postconf complete -F _ldapwhoami ldapwhoami complete -F _ldapaddmodify ldapadd complete -F _launchctl launchctl complete -F _java java complete -F _stream stream complete -F _filedir_xspec oodraw -- Regards, Peng
Re: Why complete doesn't print anything if it is called in a bash script?
On Sat, Nov 12, 2011 at 10:01 AM, Andreas Schwab wrote: > Peng Yu writes: > >> It is strange to me why complete doesn't print anything when it is >> called in a bash script. I must have misunderstood some fundamentals. >> Does anybody know why? Thanks! > > If complete does not print anything then there are no completions > defined. The question is why. I have source my bashrc, as you can see there are completions defined in the interactive shell. -- Regards, Peng
Re: Why complete doesn't print anything if it is called in a bash script?
On Sat, Nov 12, 2011 at 10:18 AM, Chet Ramey wrote: > On 11/12/11 10:41 AM, Peng Yu wrote: >> Hi, >> >> It is strange to me why complete doesn't print anything when it is >> called in a bash script. I must have misunderstood some fundamentals. >> Does anybody know why? Thanks! > > Since complete happily shows completions when run from a shell script, > there must be code in your bashrc that prevents them from being > defined if the shell is not interactive. Thank you for reminding me! That's indeed the case (shown below is from the bashrc file). case $- in *i*) [[ -f /opt/local/etc/bash_completion ]] && . /opt/local/etc/bash_completion ;; esac -- Regards, Peng
converting array to string by quoting each element for eval
Hi,
I find that I have to make a program quotearg.sh to convert an array
to a string by quoting each element. So that it be used for eval.
I'm not sure if there is a way that I can do eval in bash without
having to use quotearg.sh. If there is no such a way, should
quotearg.sh be added in bash (if it is not available in bash yet), as
it provides a fundamental functionality?
~/linux/bin/src/bash/quotearg/main$ cat ./main.sh
#!/usr/bin/env bash
../quotearg.sh a b c
../quotearg.sh "'" ' ' '"'
../quotearg.sh 'a' 'a b'
echo
args=('a' 'a b')
cmd="printf 'x%sx\n' ${args[@]}"
eval "$cmd"
echo #the following is what I want, the above is not.
args=('a' 'a b')
arg_string=`../quotearg.sh "${args[@]}"`
cmd="printf 'x%sx\n' $arg_string"
eval "$cmd"
~/linux/bin/src/bash/quotearg/main$ ./main.sh
'a' 'b' 'c'
''\''' ' ' '"'
'a' 'a b'
xax
xax
xbx
xax
xa bx
--
Regards,
Peng
Re: converting array to string by quoting each element for eval
> Why not use the array instead of making it into a single string?
>
> $cmd "${args[@]}"
>
> Why are you using eval or quotearg.sh? It sounds as if you are
> making the process more complicated than it need be.
For the examples that I gave, probably it is not necessary.
I'm yet to make a concrete complex example to demonstrate its
usefulness in practice. But I think that it is easy to imagine that
there will be some complex commands that are composed by concatenating
multiple strings to be evaled, in which case this may be useful.
--
Regards,
Peng
Re: converting array to string by quoting each element for eval
> In any case, combining a command and its arguments in a single > string is almost always the wrong way to go about it. Please compare the two scripts and see if the second one makes more sense. /tmp$ cat not_convert_args_to_string.sh #!/bin/bash options="$2" find $1 $options echo find $1 $options /tmp$ cat convert_args_to_string.sh #!/bin/bash options="$2" cmd="find $1 $options" eval "$cmd" echo $cmd /tmp$ ./not_convert_args_to_string.sh . "-type f -name '*'" find: `./cvcd': Permission denied find . -type f -name '*' /tmp$ ./convert_args_to_string.sh . "-type f -name '*'"|head find: `./cvcd': Permission denied ./.main.sh.swp ./0001e4ecf6175 ./alm.log ./amt.log ./convert_args_to_string.sh ./FLEXnet/11.5.0.0 build 56285Macrovision ./FLEXnet/524288-16F7558F-328B-4dc3-BEDF-095C1F14FFF1 ./FLEXnet/524288-34E9EE98-50ED-4c6c-BD0F-F539123FD064 ./FLEXnet/524288-85A0F138-527D-4012-8175-79A3AEA4152E ./FLEXnet/freCqflgCxFrwiBvBiCadibCwg -- Regards, Peng
Re: converting array to string by quoting each element for eval
On Tue, Nov 15, 2011 at 6:43 PM, Chris F.A. Johnson wrote: > On Tue, 15 Nov 2011, Peng Yu wrote: > >>> In any case, combining a command and its arguments in a single >>> string is almost always the wrong way to go about it. >> >> Please compare the two scripts and see if the second one makes more sense. >> >> /tmp$ cat not_convert_args_to_string.sh >> #!/bin/bash >> >> options="$2" >> find $1 $options >> echo find $1 $options > > More sensible would be to have each option a separate argument and > do: > > location=$1 > shift > find "$location" "$@" No. My real example use getopt. If I have each option in a separate argument, I need to know all the possible arguments to find, which is not a viable route. >> /tmp$ cat convert_args_to_string.sh >> #!/bin/bash >> >> options="$2" >> cmd="find $1 $options" >> eval "$cmd" >> echo $cmd > > See above. > >> /tmp$ ./not_convert_args_to_string.sh . "-type f -name '*'" >> find: `./cvcd': Permission denied >> find . -type f -name '*' > > Use 'set -x' to see exactly what your script is doing. How to pass the option "-type f -name '*'" correctly? /tmp$ ./not_convert_args_to_string.sh . "-type f -name '*'" + options='-type f -name '\''*'\''' + find . -type f -name ''\''*'\''' find: `./cvcd': Permission denied + echo find . -type f -name ''\''*'\''' find . -type f -name '*' -- Regards, Peng
Re: converting array to string by quoting each element for eval
> Then why don't you post that?
Please take a look and see if you have a better solution than the
following code without using quotearg.sh.
/tmp/tmp$ ll *
c d:
total 0
-rw-r--r-- 1 pengy wheel 0 2011-11-15 20:18:11 xx
a b:
total 0
-rw-r--r-- 1 pengy wheel 0 2011-11-15 20:18:15 yy
/tmp/tmp$ ../convert_args_to_string.sh 'a b' 'c d' -O "-type f -name '*'"
TEMP= -O '-type f -name '\''*'\''' -- 'a b' 'c d'
a b/yy
c d/xx
find 'a b' 'c d' -type f -name '*'
/tmp/tmp$ cat ../convert_args_to_string.sh
#!/bin/bash
TEMP=`getopt -o O: --long options: -n "${script_name}.sh" -- "$@"`
echo TEMP=$TEMP
if [ $? != 0 ] ; then printf "Terminating...\n" >&2 ; exit 1 ; fi
eval set -- "$TEMP"
abspath_script=`readlink -f -e "$0"`
script_absdir=`dirname "$abspath_script"`
while true ; do
case "$1" in
-O|--options)
options="$2"
shift 2
;;
--)
shift
break
;;
*)
echo "Internal error!"
exit 1
;;
esac
done
arg_string=`quotearg.sh "$@"`
cmd="find $arg_string $options"
eval "$cmd"
echo $cmd
--
Regards,
Peng
Re: converting array to string by quoting each element for eval
Hi Greg, > **NEVER** use getopt(1). It is broken. It cannot be made to work > correctly. Its entire design is flawed. I don't see these warnings in my systems (macports and ubuntu) (This is version of getopt on macports and ubuntu is free, I don't see there is a reason that getopt can not be ported to the two systems that you mentioned). All I see that is relevant is the following. I don't think that just because that it has a BUGS section in the manpage, it can be called broken. man bash also has BUGS section, is bash considered as broken? BUGS getopt(3) can parse long options with optional arguments that are given an empty optional argument (but can not do this for short options). This getopt(1) treats optional arguments that are empty as if they were not present. The syntax if you do not want any short option variables at all is not very intuitive (you have to set them explicitely to the empty string). AUTHOR Frodo Looijaard Note that it doesn't mean that I am resistant to getopts. It is just that I don't think that your logic is valid. But I will read more about getopts to see if it is necessary to convert from getopt to getopts. > ./myscript . -type f -name '*' To support your claim, tell me what myscript would be if the commands ./myscript 'a b' 'c d' -type f -name '*" ./myscript 'a b' -type f -name '*" actually do find 'a b' 'a d' -maxdepth 1 -type f -name '*" find 'a b' -maxdepth 1 -type f -name '*" -- Regards, Peng
Re: converting array to string by quoting each element for eval
> And that is enough of this nonsense. I have cited three official manuals > for you already. Let's move on. I don't get it. Do you mean both traditional getopt and Debian getopt are broken. To me it seems that Debian getopt is made to address the short coming of transitional getopt. Yet you still think Debian getopt is broken? > Now that we know the goal, it's simple enough: No. That is not my goal. It is just a simplification of my goal. It is really hard to enumerate all the possible use cases, but I will try. In additional to the use cases I stated in the previous email, let's consider some more: ./myscript 'a b' 'c d' -o output.txt -type f -name '*' or ./myscript 'a b' 'c d' -output output.txt -type f -name '*' or ./myscript -output output.txt -type f -name '*' 'a b' 'c d' or ./myscript -type f -name '*' 'a b' -output output.txt 'c d' is equivalent find 'a b' 'a d' -maxdepth 1 -type f -name '*' > output.txt -- Regards, Peng
Re: converting array to string by quoting each element for eval
> You may safely use getopts (the builtin). Never getopt. If my understanding is correct, 'getopts' doesn't support the long format. Hence, it does not satisfy my need and I shall not use it. -- Regards, Peng
How to directly modify $@?
Hi, I don't see if there is a way to directly modify $@. I know 'shift'. But I'm wondering if there is any other way to modify $@. ~$ 1=x -bash: 1=x: command not found ~$ @=(a b c) -bash: syntax error near unexpected token `a' -- Regards, Peng
How to protect > and interpret it later on? (w/o using eval)
Hi, ~$ cat ../execute.sh #!/usr/bin/env bash echo "$@" "$@" $ ../execute.sh ls >/tmp/tmp.txt $ cat /tmp/tmp.txt #I don't want "ls" be in the file ls main.sh '>' will not work unless eval is used in execute.sh. $ ../execute.sh ls '>' /tmp/tmp.txt ls > /tmp/tmp.txt ls: cannot access >: No such file or directory /tmp/tmp.txt How to make execute protect > and interpret it later on w/o using eval? -- Regards, Peng
Re: How to protect > and interpret it later on? (w/o using eval)
> WHAT are you trying to DO? I think that you might completely miss my point. I try to explain it better. Let me know if this time it makes more sense to you. I want to execute any command as if the 'execute.sh' does not present, except that I want to print the command so that I know want the command is executed. (This can be used when I call several commands in a script and I know what part of the output associated to what command). E.g. I can run ls > /tmp/tmp.txt When I call, execute.sh ls > /tmp/tmp.txt I want it actually to do echo "ls > /tmp/tmp.txt" ls > /tmp/tmp.txt Note that I could define execute.sh such that execute.sh "ls > /tmp/tmp.txt" means echo "ls > /tmp/tmp.txt" eval "ls > /tmp/tmp.txt" But this interface of execute.sh is not as good the previous one. Note that there could be other symbols that bash normal process, such as '2>&1'. I'm looking for a general solution, Pierre's answer is not as general as I want. The FAQ http://mywiki.wooledge.org/BashFAQ/050 doesn't really answer my question. BTW, where is the help-bash mailing list mentioned (at least not on bash home page)? I have never seen it before. http://tiswww.case.edu/php/chet/bash/bashtop.html -- Regards, Peng
Re: How to protect > and interpret it later on? (w/o using eval)
> THAT will work. But why are you writing a script to read a shell command > and then execute it? There is already a program that reads shell commands This capability will be useful for debugging bash script. For example, I have a set of commands in a bash script, each of them output some thing to stdout. However, I can not tell the start and end of each output. I could have a command that does what I expect execute.sh to do. cmd1 cmd2 ... I can easily append each command with 'execute.sh', which will not only tell me the boundary of each output but also help me remember what command was executed. execute.sh cmd1 execute.sh cmd2 ... Since what I expect is not possible, the next solution is to use the eval version which requires to put quote around cmd1, cmd2... But this is very annoying, when cmd1, cmd2 themselves have the quotation marks, I have to escape these marks. So neither solution to execute.sh is ideal, although any of them is better than the other in certain situations. -- Regards, Peng
Ill positioned 'until' keyword
Hi, I looks a little wired why 'until' is the way it is now. According to the manual until is before the do-done block. until test-commands; do consequent-commands; done A common design of until in other language is that it allows the loop body be executed at least once and test the condition at the end of the run of the first time. It seems that a better of bash should also follow the practice. If I understand it correctly, the above is exact the same as the following, in which case the do done block can be executed zero time. Because of this, I think that the current 'until' is not necessary, and probably better to change its definition so that it allows the execution of the loop at least once. while ! test-commands; do consequent-commands; done In short, I'd expect the following code echo 9 (not working with the current bash). COUNTER=9 do echo COUNTER $COUNTER let COUNTER-=1 done until [ $COUNTER -lt 10 ]; I'd like to hear for what reason 'until' is designed in the way it is now. Shall we considered to at least allow an option in bash to change it meaning to the one I propose (or adding a different command, like until2, for what I proposed), which give us time to let the orignal until usage dies out. -- Regards, Peng
Re: [Help-bash] How to keep only files match the prefix when do command completion?
Hi Greg, > New users do not mess with programmable completion. Given the context, I though that it was clear that "new users" means users new to command completion. If it was not clear, I make it explicit here. -- Regards, Peng
Is the description of set -- missing in man bash or at least difficult to find?
Hi,
As I mentioned previously, there are shortcomings in man bash. Here, I
just point another example. And I hope my suggestion will be
addressed.
As a reasonable search strategy to search for how to set $@ is to
search for '$@' in man bash. The literal word '$@' appears at the
following locations.
...performed, with the exception of "$@" as explained below under Special...
...expands to a separate word. That is, "$@" is equivalent to "$1"...
...When there are no positional parameters, "$@" and $@ expand to...
...of "$@" and "${name[@]}" as explained above (see PARAMETERS)...
Search for 'set --' returns nothing. And search for '--' is prohibited
as there are too many of them. If the manual discusses how to 'set
$@', then it is at least hard to find. My suggestion is to add a new
paragraph to the existing discussion of $@, so that by searching $@,
readers can easily see how set $@.
@ Expands to the positional parameters, starting from one. When
the expansion occurs within double quotes, each parameter
expands to a separate word. That is, "$@" is equivalent to "$1"
"$2" ... If the double-quoted expansion occurs within a word,
the expansion of the first parameter is joined with the begin-
ning part of the original word, and the expansion of the last
parameter is joined with the last part of the original word.
When there are no positional parameters, "$@" and $@ expand to
nothing (i.e., they are removed).
As others pointed out LDP/abs is a more readable document, the
following link is a much better document on helping me to find how to
set "$@".
http://tldp.org/LDP/abs/html/internalvariables.html
--
Regards,
Peng
Re: Is the description of set -- missing in man bash or at least difficult to find?
> Second, just search for the 'set' builtin, near the bottom of the man page. Thank for clarifying the usage of set. I looked closely to the document of set. I just find another problem, it says the following. However, the description of -- way down below. It should be the option be described. A rule of thumb is that the order of the description of the options should be the same as the order in the following line. set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...] But my main point is if a person only knows the keyword $@, he will not be able to find how to set it in the manual. The description of 'set --' should also be added to the description of $@ to explain how to set $@. Also, "If no arguments follow this option, then the positional parameters are unset. Otherwise, the positional parameters are set to the args, even if some of them begin with a -." should be rewritten as "If no arguments follow this option, then the positional parameters $@ are unset. Otherwise, the positional parameters $@ are set to the args, even if some of them begin with a -." so that $@ is searchable. -- Regards, Peng
Re: Is the description of set -- missing in man bash or at least difficult to find?
> +1 vote on getting the parameters listed with a leading dollar sign. > The individual single character is difficult to search for but the > combination of "$@" and so forth for the others is a useful search > string. I have often wanted the manual to include the "$@" > combination instead of just the "@" name. I agree $@ is better than @. But not to repeat myself again, did you get my major point that I have restated to DJ Mills? -- Regards, Peng
Re: Is the description of set -- missing in man bash or at least difficult to find?
> There are shortcomings in _the man documentation format_ and one of them > is that it doesn't work (at least for me...) when the documentation is > longer than one screen or thereabouts. I've pretty much come to the > conclusion that any man page that is over a couple of hundred lines is > a waste of my time and should probably not even exist in the first > place. Hi CJ, You didn't get my point. Please see my reply to DJ Mills, if my first email is not clear enough to you. The shortcomings is not in the man format. Even if it is in the man format, it can be compensated in the way that I mentioned. -- Regards, Peng
Specify completion without name
Hi, I want to customize the command completion for completing executables, I want to search in a file (which includes all the executables in PATH) rather than the default PATH variable. But I don't see how to do so, as the following help indicates that it can only configure how to complete the arguments of a command. Does anybody know how to configure command completion for the name itself rather than its arguments? Thanks! ~/Downloads$ help complete complete: complete [-abcdefgjksuv] [-pr] [-o option] [-A action] [-G globpat] [-W wordlist] [-P prefix] [-S suffix] [-X filterpat] [-F function] [-C command] [name ...] For each NAME, specify how arguments are to be completed. If the -p option is supplied, or if no options are supplied, existing completion specifications are printed in a way that allows them to be reused as input. The -r option removes a completion specification for each NAME, or, if no NAMEs are supplied, all completion specifications. -- Regards, Peng
Re: Specify completion without name
> empty lines. There is no programmable completion mechanism to complete > on non-empty command names. I'm wondering if it is worthwhile to add such a feature. I have run into the problem that it is very slow to command complete an incomplete command especially when other programs are accessing the disk (note that I frequently open new terminals, so the caching done within a bash process does not help me much). If I can configure how to complete on non-empty command names, I could just check a file with all the commands in PATH are stored. By checking just a single file, presumable the search can be much faster than searching many directories. -- Regards, Peng -- Regards, Peng
Re: Specify completion without name
> Presumably you would also include aliases, shell builtins, and functions > in this file. Yes. I just want to replace executables in PATH by the result from my custom function. I think that aliases, builtins, and functions are all in the memory of bash already, so it doesn't take extra time to search them from bash. Therefore, the ideal behaviors is that bash still search for aliases, builtins and functions, and in addition check the results returned by my custom function. Hence, my custom function should not return anything about them (this should be expect at least by default). -- Regards, Peng
Re: Specify completion without name
> I would envision that such a completion function would assemble its list > of possible completions by using your read-from-a-file mechanism and > augment the list using compgen -a/compgen -b/compgen -A function. It > would probably also want to handle glob patterns and expand them to > potentially multiple completions, but that gets tricky. I did not know that it is so simple to get the alias (compgen -a), buildins (compgen -b) and functions (compgen -A function) as you mentioned. Once I know these, I agree with you that bash need not handle these internally, rather user can call these three functions directly. But beware to clearly document these by giving working EXAMPLE code which include these three commands (not just text explanation without working code, by "working code" I mean code snippet is discouraged, a complete completion function should be provided). BTW, as I mentioned several times the bash man favors document maintainer rather readers. For example, the following help doesn't help me much when I want to learn how to use compgen. ~$ help compgen compgen: compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-P prefix] [-S suffix] [-X filterpat] [-F function] [-C command] [word] Display the possible completions depending on the options. Intended to be used from within a shell function generating possible completions. If the optional WORD argument is supplied, matches against WORD are generated. The manpage also use a reference rather than list all the options directly. Readers have to jump to complete to understand how to use compgen. This is also inconvenient to users. Generate possible completion matches for word according to the options, which may be any option accepted by the complete builtin If you consider it repetitive to discuss the same option twice in both compgen and complete, at least, you can expand "help compgen" to describe all the options (merge the current description of compgen and complete in man). Other help messages are so concise that they are not very helpful for learning how to use them. I'd suggest change all of them as well. -- Regards, Peng
Re: Specify completion without name
> The bash man page already has ~70 pages manual. I don't like it to grow to > ~700 pages (like the ABS Guide) with all the working examples you expected. > :) Do you use search at all? :) If you use search, it doesn't really matter if is a 700 page manual. -- Regards, Peng
cd won't change the prompt if the command is typed in the vi editor (vi mode).
Hi, I have vi mode set. set -o vi. Then I type v to enter the vi editor. In the vi editor, I type 'cd /tmp'. Then, I get the following screen output. Notice that the prompt does not change immediately after the cd command. Could anybody reproduce this behavior? Thanks. ~$ cd /tmp ~$ echo $PWD /tmp /tmp$ -- Regards, Peng
"echo" does not follow the "getopt" convention
Hi, The following shows that echo does not following the "getopt" convection. Is it better to make all bash internal command following the getopt convention? ~$ echo -n ~$ echo -n -n ~$ echo -n -- -n # I think that the output should just be "-n" not "-- -n". -- -n~$ http://software.frodo.looijaard.name/getopt/ -- Regards, Peng Yu, Ph.D. Assistant Professor Dept. Electrical and Computer Engineering & TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering (CBGSE) Texas A&M University Office: 215F WEB Phone: (979) 320-9822 Email: pe...@tamu.edu http://yubiolab.wordpress.com
How to change the command completion behavior in bash
If I have the following in the command line, ~/.bash when I type , it will become /home/my_user_name/.bash I'm wondering if it is possible to configure bash command completion, so that it will still be '~/.bash'
Re: How to change the command completion behavior in bash
On Mon, Nov 16, 2009 at 8:30 AM, Chet Ramey wrote: >> If I have the following in the command line, >> >> ~/.bash >> >> when I type , it will become /home/my_user_name/.bash >> >> I'm wondering if it is possible to configure bash command completion, >> so that it will still be '~/.bash' > > You don't say what version of bash you're using, but bash-3.2 and bash-4.0 > both preserve the tilde by default. Here are my bash version and /etc/inputrc. I don't find where it changes the default behavior $ bash --version GNU bash, version 3.2.39(1)-release (x86_64-pc-linux-gnu) Copyright (C) 2007 Free Software Foundation, Inc. $ cat /etc/inputrc # /etc/inputrc - global inputrc for libreadline # See readline(3readline) and `info rluserman' for more information. # Be 8 bit clean. set input-meta on set output-meta on # To allow the use of 8bit-characters like the german umlauts, comment out # the line below. However this makes the meta key not work as a meta key, # which is annoying to those which don't need to type in 8-bit characters. # set convert-meta off # try to enable the application keypad when it is called. Some systems # need this to enable the arrow keys. # set enable-keypad on # see /usr/share/doc/bash/inputrc.arrows for other codes of arrow keys # do not bell on tab-completion # set bell-style none # set bell-style visible # some defaults / modifications for the emacs mode $if mode=emacs # allow the use of the Home/End keys "\e[1~": beginning-of-line "\e[4~": end-of-line # allow the use of the Delete/Insert keys "\e[3~": delete-char "\e[2~": quoted-insert # mappings for "page up" and "page down" to step to the beginning/end # of the history # "\e[5~": beginning-of-history # "\e[6~": end-of-history # alternate mappings for "page up" and "page down" to search the history # "\e[5~": history-search-backward # "\e[6~": history-search-forward # mappings for Ctrl-left-arrow and Ctrl-right-arrow for word moving "\e[1;5C": forward-word "\e[1;5D": backward-word "\e[5C": forward-word "\e[5D": backward-word "\e\e[C": forward-word "\e\e[D": backward-word $if term=rxvt "\e[8~": end-of-line "\eOc": forward-word "\eOd": backward-word $endif # for non RH/Debian xterm, can't hurt for RH/Debian xterm # "\eOH": beginning-of-line # "\eOF": end-of-line # for freebsd console # "\e[H": beginning-of-line # "\e[F": end-of-line $endif $ cat ~/.inputrc set editing-mode vi set bell-style none "\e[A": history-search-backward ## up-arrow
Re: How to change the command completion behavior in bash
On Mon, Nov 16, 2009 at 4:50 AM, Henning Garus wrote: > On Sun, Nov 15, 2009 at 08:31:38PM -0600, Peng Yu wrote: >> If I have the following in the command line, >> >> ~/.bash >> >> when I type , it will become /home/my_user_name/.bash >> >> I'm wondering if it is possible to configure bash command completion, >> so that it will still be '~/.bash' >> > > Add > > set expand-tilde off > > to your ~/.inputrc . However off is the default value, so you could > try to find out where it is set to on and remove that. > > See "Readline Variables" in man bash. I add set expand-tilde off to my ~/.inputrc. Then I login again. Then I type the following after bash prompt cd ~ Later, if I type after ~, ~ still expands to the abspath of my home directory. I'm confused why 'set expand-tilde off' does not change the behavior of bash. Regards, Peng
Re: How to change the command completion behavior in bash
On Tue, Nov 17, 2009 at 1:15 PM, Chet Ramey wrote: > Peng Yu wrote: >> On Mon, Nov 16, 2009 at 8:30 AM, Chet Ramey wrote: >>>> If I have the following in the command line, >>>> >>>> ~/.bash >>>> >>>> when I type , it will become /home/my_user_name/.bash >>>> >>>> I'm wondering if it is possible to configure bash command completion, >>>> so that it will still be '~/.bash' >>> You don't say what version of bash you're using, but bash-3.2 and bash-4.0 >>> both preserve the tilde by default. > > I think I may have been confused. If you're not doing command completion > with the tilde-prefixed string (that is, if it's an argument to another > command already on the line), you're probably using the > bash_completion set of programmable completions, and the completion > specification for the command to which this is an argument is probably > expanding the tilde. > > I assumed you were trying to complete the above string as a command, not > an argument to a command. > > What is the full command line on which you're attempting completion? I'm trying to complete an argument rather than a command as I just replied in the previous message.
What files are source in bash login shell?
I make my ~/.bash_profile empty. I still see $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games I checked /etc/profile and /etc/bash.bashrc. But I don't PATH is set in the two files. I'm wondering from which file PATH is set. BTW, my system is ubuntu.
Re: What files are source in bash login shell?
On Tue, Nov 17, 2009 at 3:12 PM, Bob Proulx wrote: > Peng Yu wrote: >> I make my ~/.bash_profile empty. I still see >> >> $ echo $PATH >> /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games > > What is in your ~/.bashrc file? > >> I checked /etc/profile and /etc/bash.bashrc. But I don't PATH is set >> in the two files. I'm wondering from which file PATH is set. BTW, my >> system is ubuntu. > > Are you sure that it isn't being set in /etc/profile? > > It may be the compiled in value. Run strings on your binary and see > what is there. On my Debian system: > > $ grep /usr/bin /etc/profile > PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" > PATH="/usr/local/bin:/usr/bin:/bin:/usr/games" > > $ strings /bin/bash | grep /usr/bin > /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin Here are what I have. $ grep /usr/bin /etc/profile $ strings /bin/bash | grep /usr/bin /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
Command completion considering characters after the cursor?
Suppose I have 'some.sh' in my command line, and my cursor is at '.' $some.sh Suppose there is only one command that start with 'some', which is 'something.sh'. After I type TAB, I will have 'something.sh.sh' in my command line. $something.sh.sh I'm wondering if there is a way to configure bash, so that I will get 'something.sh' rather than 'something.sh.sh'.
Re: Command completion considering characters after the cursor?
On Mon, Jan 18, 2010 at 10:00 AM, Chet Ramey wrote: > On 1/18/10 9:49 AM, Peng Yu wrote: >> Suppose I have 'some.sh' in my command line, and my cursor is at '.' >> >> $some.sh >> >> Suppose there is only one command that start with 'some', which is >> 'something.sh'. After I type TAB, I will have 'something.sh.sh' in my >> command line. >> >> $something.sh.sh >> >> I'm wondering if there is a way to configure bash, so that I will get >> 'something.sh' rather than 'something.sh.sh'. > > There is nothing directly analogous in bash. The closest thing is the > `skip-completed-text' readline variable in bash-4.1/readline-6.1, but > that will not help in this case. Can I request this feature be added in future version of bash?
Argument list too long (how to remove the limit)
I got the following message. Is there a way to configure bash such that there is not a limit like this? /bin/bash: Argument list too long
Colored command completion
I'm wondering if it is possible to color the files shown by command completion (i.e. after typing ). The color scheme can be of the same as the one used in "ls --color=auto". By this way, it is easier to see what the type of the file is.
Circulate matches in command completion?
Suppose I file 'a1.txt' and 'a2.txt' in my current directory. When I type 'cat a' then TAB, it will show me 'a1.txt' and 'a2.txt'. If I type TAB repeatedly, it will always show me the same thing. However, a better response might be 1. complete the command to 'cat a1.txt' at the 2nd TAB, 2. complete the command to 'cat a2.txt' at the 3rd TAB, 3. return to the original 'cat a' at the 4th TAB, 4. complete the command to 'cat a1.txt' again at the 5th TAB. I'm wondering if there is a way to configure bash this way.
Re: Circulate matches in command completion?
On Thu, Feb 11, 2010 at 9:58 AM, Chet Ramey wrote: > On 2/11/10 10:54 AM, Peng Yu wrote: >> Suppose I file 'a1.txt' and 'a2.txt' in my current directory. When I >> type 'cat a' then TAB, it will show me 'a1.txt' and 'a2.txt'. If I >> type TAB repeatedly, it will always show me the same thing. >> >> However, a better response might be >> 1. complete the command to 'cat a1.txt' at the 2nd TAB, >> 2. complete the command to 'cat a2.txt' at the 3rd TAB, >> 3. return to the original 'cat a' at the 4th TAB, >> 4. complete the command to 'cat a1.txt' again at the 5th TAB. >> >> I'm wondering if there is a way to configure bash this way. > > bind 'TAB:menu-complete' This is helpful. But it is not exactly what I'm looking for. I still want to show 'a1.txt' and 'a2.txt' at the 1st TAB. The above bind command gives me 'cat a1.txt' directly at the 1st TAB.
Re: Circulate matches in command completion?
On Thu, Feb 11, 2010 at 10:36 AM, Chet Ramey wrote: > On 2/11/10 11:05 AM, Peng Yu wrote: >> On Thu, Feb 11, 2010 at 9:58 AM, Chet Ramey wrote: >>> On 2/11/10 10:54 AM, Peng Yu wrote: >>>> Suppose I file 'a1.txt' and 'a2.txt' in my current directory. When I >>>> type 'cat a' then TAB, it will show me 'a1.txt' and 'a2.txt'. If I >>>> type TAB repeatedly, it will always show me the same thing. >>>> >>>> However, a better response might be >>>> 1. complete the command to 'cat a1.txt' at the 2nd TAB, >>>> 2. complete the command to 'cat a2.txt' at the 3rd TAB, >>>> 3. return to the original 'cat a' at the 4th TAB, >>>> 4. complete the command to 'cat a1.txt' again at the 5th TAB. >>>> >>>> I'm wondering if there is a way to configure bash this way. >>> >>> bind 'TAB:menu-complete' >> >> This is helpful. But it is not exactly what I'm looking for. I still >> want to show 'a1.txt' and 'a2.txt' at the 1st TAB. The above bind >> command gives me 'cat a1.txt' directly at the 1st TAB. > > Look at the 'show-all-if-ambiguous' option. The combination may do what > you want. set show-all-if-ambiguous On bind 'TAB:menu-complete' I typed in the above two commands. It seems that command completion is the same as if I only typed in the second command. Do you know why?
Re: Circulate matches in command completion?
On Fri, Feb 12, 2010 at 1:36 PM, DennisW wrote: > On Feb 11, 11:33 am, Peng Yu wrote: >> On Thu, Feb 11, 2010 at 10:36 AM, Chet Ramey wrote: >> > On 2/11/10 11:05 AM, Peng Yu wrote: >> >> On Thu, Feb 11, 2010 at 9:58 AM, Chet Ramey wrote: >> >>> On 2/11/10 10:54 AM, Peng Yu wrote: >> >>>> Suppose I file 'a1.txt' and 'a2.txt' in my current directory. When I >> >>>> type 'cat a' then TAB, it will show me 'a1.txt' and 'a2.txt'. If I >> >>>> type TAB repeatedly, it will always show me the same thing. >> >> >>>> However, a better response might be >> >>>> 1. complete the command to 'cat a1.txt' at the 2nd TAB, >> >>>> 2. complete the command to 'cat a2.txt' at the 3rd TAB, >> >>>> 3. return to the original 'cat a' at the 4th TAB, >> >>>> 4. complete the command to 'cat a1.txt' again at the 5th TAB. >> >> >>>> I'm wondering if there is a way to configure bash this way. >> >> >>> bind 'TAB:menu-complete' >> >> >> This is helpful. But it is not exactly what I'm looking for. I still >> >> want to show 'a1.txt' and 'a2.txt' at the 1st TAB. The above bind >> >> command gives me 'cat a1.txt' directly at the 1st TAB. >> >> > Look at the 'show-all-if-ambiguous' option. The combination may do what >> > you want. >> >> set show-all-if-ambiguous On >> bind 'TAB:menu-complete' >> >> I typed in the above two commands. It seems that command completion is >> the same as if I only typed in the second command. Do you know why? > > The first command should be: > > bind 'set show-all-if-ambiguous On' bind 'set show-all-if-ambiguous On' bind 'TAB:menu-complete' I typed the above commands in the command line, but I still don't see the print out of all matches. Would you please let me know how to debug what is wrong?
Is there a special variable for the directory where the script is in?
$0 gives the file name of the script. I could use several shell command to get the directory where the script is in. But I'm wondering if there is an easy-to-use variable that refers to the directory where the script is in?
Re: Circulate matches in command completion?
On Fri, Feb 12, 2010 at 10:43 AM, Chet Ramey wrote: > On 2/11/10 6:14 PM, Peng Yu wrote: > >> bind 'set show-all-if-ambiguous On' >> bind 'TAB:menu-complete' >> >> I typed the above commands in the command line, but I still don't see >> the print out of all matches. Would you please let me know how to >> debug what is wrong? > > The combination of those two commands does exactly what you want in > bash-4.1. Menu completion on previous versions of bash behaves > differently. My bash is of the following version. I guess this is the reason what the command is not working? $ bash --version GNU bash, version 3.2.39(1)-release (x86_64-pc-linux-gnu) Copyright (C) 2007 Free Software Foundation, Inc.
Why tab is not colored?
My grep is aliased to "grep --color=auto". I then use grep "", where is a tab character. But the result is not colored. How to make the tabs colored?
How cd to a directory with special characters like environment\<\-?
I make the following directory and try to cd to it. But I can't. Could you let me know what is the correct way of doing so? $ mkdir environment\<\- $ cd environmen\<\- -bash: cd: environmen<-: No such file or directory -- Regards, Peng
Re: How cd to a directory with special characters like environment\<\-?
On Thu, Apr 8, 2010 at 4:58 PM, Peng Yu wrote: > I make the following directory and try to cd to it. But I can't. Could > you let me know what is the correct way of doing so? > > $ mkdir environment\<\- > $ cd environmen\<\- > -bash: cd: environmen<-: No such file or directory Never mind. I get it. -- Regards, Peng
How to start bash without inheriting any environment variables and user level profiles (such as .bash_profile)?
I'm wondering how to start bash without inheriting any environment variables and user level profiles (such as .bash_profile). Would you please let me know what option to use? -- Regards, Peng
How to control the width of a number?
Hi,
I want $page has three digits. If it is less than 100, prefix it with
0. Is there an easy way to do so in bash?
for i in `seq 28 55`;
do
page=`echo '148-('$i'-28)*2'|bc`
echo $i $page
done
--
Regards,
Peng
Re: How to control the width of a number?
On Tue, May 4, 2010 at 10:28 AM, Dennis Williamson
wrote:
> for i in {28..55}
> # or: for ((i=28; i<=55; i++))
> do
> (( page = 148 - ( i - 28 ) * 2 ))
> printf '$d $03d\n' $i $page
> done
I assume that you mean '%d %03d'.
> This eliminates external calls to bc and seq in addition to zero-padding
> $page.
It is good to know this trick.
> On Tue, May 4, 2010 at 8:05 AM, Peng Yu wrote:
>> Hi,
>>
>> I want $page has three digits. If it is less than 100, prefix it with
>> 0. Is there an easy way to do so in bash?
>>
>> for i in `seq 28 55`;
>> do
>> page=`echo '148-('$i'-28)*2'|bc`
>> echo $i $page
>> done
>>
>> --
>> Regards,
>> Peng
>>
>>
>>
>
--
Regards,
Peng
How to overwrite a symbolic link?
Suppose that I have a symbolic link link1 pointing to file1. When I write to link1, I don't want file1 change. I want it to remove the link generated a new file and write to it. pipe '>' will change file 1. I'm wondering if there is way to do so, so that I don't have to test whether it is a symbolic link or not explicitly. -- Regards, Peng
Re: How to overwrite a symbolic link?
On Thu, May 6, 2010 at 10:53 AM, Pierre Gaston wrote: > On Thu, May 6, 2010 at 5:53 PM, Peng Yu wrote: >> Suppose that I have a symbolic link link1 pointing to file1. When I >> write to link1, I don't want file1 change. I want it to remove the >> link generated a new file and write to it. >> >> pipe '>' will change file 1. I'm wondering if there is way to do so, >> so that I don't have to test whether it is a symbolic link or not >> explicitly. >> > rm link1 Is there a way to overload operators like '>' and '>>' in bash, just as overloading in C++, etc. Suppose I have already made some bash program using '>' and '>>' without thinking about symbolic link, but I begin aware of them later. I would be cumbersome to add a test statement and deciding whether 'rm' or not for each usage of '>' and '>>'. A more general question is how to change the behavior of a program (for example compiled from C code) to delete symbolic link and write a new file, without recompiling the program. -- Regards, Peng
Re: How to overwrite a symbolic link?
On Thu, May 6, 2010 at 5:36 PM, Bob Proulx wrote: > Peng Yu wrote: >> Is there a way to overload operators like '>' and '>>' in bash, just >> as overloading in C++, etc. Suppose I have already made some bash >> program using '>' and '>>' without thinking about symbolic link, but I >> begin aware of them later. I would be cumbersome to add a test >> statement and deciding whether 'rm' or not for each usage of '>' and >> '>>'. > > It sounds to me like you are trying to implement a "script space" > version of copy-on-write semantics? Perhaps you should investigate > using one of the filesystem based solutions. It would probably give > you a better result. > >> A more general question is how to change the behavior of a program >> (for example compiled from C code) to delete symbolic link and write a >> new file, without recompiling the program. > > A Comment: Symbolic links are designed to be transparent. Normal > programs are not aware of them. > > You could probably create an LD_PRELOAD library to intercept file > modification calls and then handle them in your own code. But I think > it would be difficult to do it all completely correctly and not to > introduce bugs. I advise against it. Would you please elaborate a little more on how to use LD_PRELOAD to modify the call. If the library (for example, 'open' from stdlib.h) is statically compiled in the binary, is LD_PRELOAD going to replace it with a different 'open' function? -- Regards, Peng
Re: How to overwrite a symbolic link?
On Fri, May 7, 2010 at 9:26 AM, Marc Herbert wrote:
> Le 06/05/2010 15:53, Peng Yu a écrit :
>> Suppose that I have a symbolic link link1 pointing to file1. When I
>> write to link1, I don't want file1 change. I want it to remove the
>> link generated a new file and write to it.
>
> This is a very strange question. Symbolic links are expressly designed
> to fool everyone. Why are you using symbolic links if you do not want
> to be fooled?
>
> Please give more details about what you are trying to do.
Suppose I have N files in a directory that does some job. Lets say M
(' and '>>' and the open file function call.
This is why I ask the question in the OP. Let me know if you have any
thought on solving this problem.
--
Regards,
Peng
Re: How to overwrite a symbolic link?
On Fri, May 7, 2010 at 10:16 AM, Eric Blake wrote: > On 05/07/2010 09:02 AM, Peng Yu wrote: >> Suppose I need to modify one primary file slightly to do something a >> little bit different. But I still need to do the original job, >> therefore I need to keep it the original M files. I can copy the whole >> directory and then modify one file in the newly copied N files. But >> I'll lose track of which file has been changed later on, which is >> important to me. > > Consider using a version control system. Track the contents of your > directory under your favorite VCS, like git, and then you can use > version control commands to generate the delta for both primary and > secondary files across any state that you committed. I can't use version control for 1. I need to frequently change file names. 2. Both primary and secondary files could be of hundred of MB or even GB. > Or, for a one-shot solution, you could use a BSD union mount, where the > difference between the mount overlay and the original directory shows > exactly what was modified. The problem is that if I have many directories that form a complex copying graph. It is not possible to keep track of all the possible lineages. Also, I need to avoid change multiple copies of the same file. > But overloading bash's > and >> operators is not possible. Is it because the underlying library that used in bash doesn't support the semantic of symbolic link that I propose? Or it is because of the OS? Is it possible to modify source code of bash to change the semantics of symbolic link. -- Regards, Peng
Re: How to overwrite a symbolic link?
On Fri, May 7, 2010 at 10:41 AM, Eric Blake wrote: > On 05/07/2010 09:31 AM, Peng Yu wrote: >> On Fri, May 7, 2010 at 10:16 AM, Eric Blake wrote: >>> On 05/07/2010 09:02 AM, Peng Yu wrote: >>>> Suppose I need to modify one primary file slightly to do something a >>>> little bit different. But I still need to do the original job, >>>> therefore I need to keep it the original M files. I can copy the whole >>>> directory and then modify one file in the newly copied N files. But >>>> I'll lose track of which file has been changed later on, which is >>>> important to me. >>> >>> Consider using a version control system. Track the contents of your >>> directory under your favorite VCS, like git, and then you can use >>> version control commands to generate the delta for both primary and >>> secondary files across any state that you committed. >> >> I can't use version control for >> 1. I need to frequently change file names. >> 2. Both primary and secondary files could be of hundred of MB or even GB. > > git handles both of those situations, without too much hassle. > >>> But overloading bash's > and >> operators is not possible. >> >> Is it because the underlying library that used in bash doesn't support >> the semantic of symbolic link that I propose? Or it is because of the >> OS? >> >> Is it possible to modify source code of bash to change the semantics >> of symbolic link. > > Yes, it's possible to modify the source of bash to change how bash > treats symlinks when using the > operator. But I would advise against > it, as your fork of bash would no longer comply with POSIX, and would > probably break a lot more than it fixes. Rather, if you insist on > modifying bash, consider adding a new operator (maybe spelled '>;', > similar to the noclobber override spelling of '>|'), so that your use of > the new operator is explicit that you know what you are doing in your > scripts (if the operand of the new operator is a symlink, break the > symlink and create a file in its place instead of operating on the > target of the symlink). Is there a way to define the operator '>;' without touching the bash source code? -- Regards, Peng
Re: How to overwrite a symbolic link?
On Mon, May 10, 2010 at 6:59 AM, Marc Herbert wrote: > Le 07/05/2010 16:02, Peng Yu a écrit : >> I can copy the whole >> directory and then modify one file in the newly copied N files. But >> I'll lose track of which file has been changed later on, which is >> important to me. > > You will not lose track of the changed files: just run a recursive > diff comparing the old and new directories and you will see what > was/has changed (this is actually the poor man's version control > system). If I have X similar directories that are resulted from the copying and modifying in the above, I will end up X*(X-1) comparisons. And it is still hard to figure out the lineage of these X directories from these X*(X-1) comparisons (because I need to compare diffs of diffs). Therefore, I think that this is not a viable solution. >> Suppose I have N files in a directory that does some job. Lets say M >> (> files (say, there are a number of programs, each takes some of the M >> files to generate some of the N-M files). >> [...] >> Instead, I'd rather create symbolic link for all the N-M-1 primary >> files but copy only one remaining file and modify it. Remember, I >> can't tell which are primary files and which are derived files. So I >> can not do so. >> >> One solution is create symbolic link to N-1 files as long as I can >> overload '>' and '>>' and the open file function call. > > So you are really trying to re-invent some copy-on-write/versioning > file system by hacking symbolic links and redirections. This looks > like a lot of pain. You'd better start by looking at existing > solutions; even if none is ideal for your case, you would at least > leverage the existing knowledge and experience in this field instead > of starting from zero. http://en.wikipedia.org/wiki/Versioning_file_system http://en.wikipedia.org/wiki/Ext3cow I'm trying to understand how versioning and copy-on-write are relevant to my cases. But I don't think that they are really relevant to my cases. The closest file system that I have used is snapshot (I don't know the exact technical term, but I remember there is a '.snapshot' directory in my home, where I can find previous 1 hour, 4 hours, 1 day and 1week versions of my home directory). Please correct me if I'm wrong. These versioning file systems automatically keep different versions (modified at different time) of the same file, and doesn't allow users to choose which versions to keep and which version not to keep. This will end up to many versions that are actually not useful and it would a pain to look for the actual useful versions. Also I need the same file appear in two different directories. I think that these versioning systems may not help me on this aspect unless I use symbolic links. Therefore, the solution to my particular problem is still in hacking symbolic link. >> Let me know if you have any thought on solving this problem. > > Since you are using the wrong tool for the job I am afraid you are > going to be rather alone on this road. For right now, I think that the best solution is, instead of reloading >, >>, and related system calls, to test symbolic link and rm it and then write a new file with the same name. The trick of _ function by Dennis is useful. -- Regards, Peng
How to use variable in a range like {a..b}?
x=10
for i in {1..$x}; do echo $i; done
The above code give me
{1..10}
, rather than printing numbers from 1 to 10.
I'm wondering how to use variable in a range?
--
Regards,
Peng
How to make a directory name with '/' in it?
I tried the following command to create a dir with '/' in the name. But it only create a directory with name 'm'. Is there a way to make a directory with '/' in the name? mkdir m\/\/ -- Regards, Peng
How to autocomplete after 'which'?
When I type something after 'which', something means a command. However, bash doesn't do command completion for the argument after 'which'. Is there a way to configure bash behave depending on the context (in this case, do autocomplete after 'which')? -- Regards, Peng
Re: How to autocomplete after 'which'?
On Fri, May 21, 2010 at 10:39 AM, Chet Ramey wrote: > On 5/21/10 11:25 AM, Peng Yu wrote: >> When I type something after 'which', something means a command. >> However, bash doesn't do command completion for the argument after >> 'which'. Is there a way to configure bash behave depending on the >> context (in this case, do autocomplete after 'which')? > > You can start with `complete -c which' and look further at the > bash-completion package, which uses the bash programmable completion > framework to provide custom completions for a large number of commands. complete -c works. I'm not familar with bash-completion package. How to customize search path for each command. For exmaple, I want search in $PYTHONPATH after the command python. BTW, where is the manual for the -c option of complete. There are too many 'complete' in man bash. Would you please point me which section is relevant to complete -c. -- Regards, Peng
Re: How to autocomplete after 'which'?
On Fri, May 21, 2010 at 11:19 AM, Marc Herbert wrote: > Le 21/05/2010 16:25, Peng Yu a écrit : >> When I type something after 'which', something means a command. >> However, bash doesn't do command completion for the argument after >> 'which'. Is there a way to configure bash behave depending on the >> context (in this case, do autocomplete after 'which')? > > By the way it is better to use "type" instead of "which". "which" is > often misleading, compare for instance: > > type pwd > which pwd > > "which" is misleading in many other cases. Since pwd is a shell command, when /bin/pwd is actually used? In shells that don't have built-in pwd? -- Regards, Peng
Re: How to autocomplete after 'which'?
On Fri, May 21, 2010 at 11:06 AM, Eric Blake wrote:
> On 05/21/2010 09:50 AM, Peng Yu wrote:
>> complete -c works. I'm not familar with bash-completion package. How
>> to customize search path for each command.
>
> By using appropriate complete invocations for each command, and lots of
> shell functions.
>
>>
>> For exmaple, I want search in $PYTHONPATH after the command python.
>
> bash-completion could do that for you, too.
>
> $ complete -p python
> complete -o filenames -F _python python
> $ type _python
> _python is a function
> _python ()
> {
> local prev cur i;
> COMPREPLY=();
> cur=`_get_cword`;
> prev=${COMP_WORDS[COMP_CWORD-1]##*/};
> case "$prev" in
> -Q)
> COMPREPLY=($( compgen -W "old new warn warnall" -- "$cur" ));
> return 0
> ;;
> -W)
> COMPREPLY=($( compgen -W "ignore default all module once
> error" -- "$cur" ));
> return 0
> ;;
> -c)
> _filedir '@(py|pyc|pyo)';
> return 0
> ;;
> !(python|-?))
> [[ ${COMP_WORDS[COMP_CWORD-2]} != -@(Q|W) ]] && _filedir
> ;;
> esac;
> for ((i=0; i < ${#comp_wor...@]}-1; i++ ))
> do
> if [[ ${COMP_WORDS[i]} == -c ]]; then
> _filedir;
> fi;
> done;
> if [[ "$cur" != -* ]]; then
> _filedir '@(py|pyc|pyo)';
> else
> COMPREPLY=($( compgen -W "- -d -E -h -i -O -Q -S -t -u
> -U -v -V -W -x -c" -- "$cur" ));
> fi;
> return 0
> }
>
> Actually, I don't see any mention of PYTHONPATH in that function, so you
> may want to file an enhancement request against the bash-completion
> package to improve their _python() function to also consider PYTHONPATH,
> rather than just *.py[co] files.
>
>>
>> BTW, where is the manual for the -c option of complete. There are too
>> many 'complete' in man bash. Would you please point me which section
>> is relevant to complete -c.
>
> 'help complete' is the easiest way to see the short details; other than
> that, look for complete under 'SHELL BUILTIN COMMANDS' in the man page.
I see the following error. What is wrong with my bash?
$ complete -p python
bash: complete: python: no completion specification
$ type _python
bash: type: _python: not found
--
Regards,
Peng
Re: How to autocomplete after 'which'?
On Fri, May 21, 2010 at 12:07 PM, Eric Blake wrote: > On 05/21/2010 10:41 AM, Peng Yu wrote: >>> 'help complete' is the easiest way to see the short details; other than >>> that, look for complete under 'SHELL BUILTIN COMMANDS' in the man page. >> >> I see the following error. What is wrong with my bash? > > Nothing is wrong with bash. Bash is telling you that you have not yet > installed a completion handler for python. > > But it _is_ a sign that you have not installed the bash-completion > package, nor installed completions manually. > >> >> $ complete -p python >> bash: complete: python: no completion specification >> $ type _python >> bash: type: _python: not found > > What's your distro? On fedora, do 'yum install -y bash-completion'. Or > get it yourself: http://bash-completion.alioth.debian.org/files/ > > Then start a new shell, and compare the difference. I installed bash-completion. Then I start a new shell. But I still see the above error messages. $ sudo apt-get install bash-completion [sudo] password for administrator: Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: bash-completion 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 124kB of archives. After this operation, 479kB of additional disk space will be used. Get:1 http://escalade.imgen.bcm.tmc.edu hardy/main bash-completion 20060301-3ubuntu3 [124kB] Fetched 124kB in 0s (4413kB/s) Selecting previously deselected package bash-completion. (Reading database ... 66941 files and directories currently installed.) Unpacking bash-completion (from .../bash-completion_20060301-3ubuntu3_all.deb) ... Setting up bash-completion (20060301-3ubuntu3) ... -- Regards, Peng
Re: How to autocomplete after 'which'?
> You will need to source the file that contains the functions: > > source /etc/bash_completions > > The installation you did most likely added something like this to your > ~/.bashrc: > > # enable programmable completion features (you don't need to enable > # this, if it's already enabled in /etc/bash.bashrc and /etc/profile > # sources /etc/bash.bashrc). > if [ -f /etc/bash_completion ]; then > . /etc/bash_completion > fi The above code changed the behavior of, for example, cd $DATA. After I type , it becomes cd \$DATA. This is not what want. When it is not sourced, typing would not change cd $DATA. Is there a way to perserve the behavior of cd $DATA? -- Regards, Peng
How only show time of files with ls?
ls -go gives me permission and file sizes. But I only want to show time and file names. Would you please let me know what command to use? -- Regards, Peng
How not to expand a environment variable when doing command completion?
When I type 'cd $HOME/.', bash will expand the command to 'cd /home/my_user_name/.'. Would you please let me know how to let bash expand the environment variable? -- Regards, Peng
Re: How not to expand a environment variable when doing command completion?
On Sat, May 22, 2010 at 3:48 PM, Peng Yu wrote: > When I type 'cd $HOME/.', bash will expand the command to 'cd > /home/my_user_name/.'. Would you please let me know how to let bash > expand the environment variable? I mean 'NOT to let bash ...'. Also, I forget to mention that /etc/bash-completion is not sourced in my .bashrc and I have make sure that it is not sourced anywhere before .bashrc. Therefore, this is a question regarding bash. Could somebody let me know how to not expand the variable. I also tried 'python $SOME_VARIABLE/', where $SOME_VARIABLE is set to a directory. Wired enough, this time $SOME_VARIABLE is not expanded at all, neither any completion to any files under the directory $SOME_VARIABLE. BTW, my bash is of version 4.1.0(2)-release (x86_64-unknown-linux-gnu). -- Regards, Peng
Re: How not to expand a environment variable when doing command completion?
> I also tried 'python $SOME_VARIABLE/', where $SOME_VARIABLE is > set to a directory. Wired enough, this time $SOME_VARIABLE is not > expanded at all, neither any completion to any files under the > directory $SOME_VARIABLE. I was confused. The above statement is not true. -- Regards, Peng
Re: How not to expand a environment variable when doing command completion?
On Tue, May 25, 2010 at 9:18 PM, Chet Ramey wrote: >> When I type 'cd $HOME/.', bash will expand the command to 'cd >> /home/my_user_name/.'. Would you please let me know how to let bash >> expand the environment variable? > > There is no setting to suppress the environment variable expansion. Bash > has behaved this way for many years. This default behavior may not be always wanted. Will a setting be added to suppress the expansion in future versions of bash? -- Regards, Peng
process substitution with a give suffix
I have a program that only accept argument with a give suffix ./program xxx.suffix If I use process substitution, which gives me /dev/fd/xx, it will not work with the program. Is there a way to make sure a suffix is added to the substitute process file handle in /def/fd/, so that the program can work with process substitution? -- Regards, Peng
cd multiple levels up?
Hello, I frequently need do cd multiple levels up. For example, cd ../.. cd ../../../../ It would be convenient to type something like "cd 2" or "cd 4". Is there a command for this? -- Regards, Peng
How to convert symbolic links pointing outside to a file?
Hi, I only want to convert symbolic links that point outside the directory to be archived to a file. But I still want to keep symbolic links point inside as symbolic links. Is there an option or a walkaround to do so in tar? -- Regards, Peng
How not to inherit any environment variable from parent process?
I use bash --noprofile to start a bash session. Since this doesn't source any profile files, I'd think that no environment variable should be set. But I still see environment variables set. Are they inherit from the parent session. Is there a way to start a bash session without using parent environment variables? -- Regards, Peng
The usage of {0..${#parameter}}
The commented line in the following bash script is not working. I
notice the following description from man bash and I think that it is
the reason. But I'm not completely sure. Would you please confirm it
for me?
Also, I'm wondering where this decision was made. Can't bash be made
more powerful by allowing the commented line? Will it cause any
problem if such thing is allowed?
#!/usr/bin/env bash
parameter=abcdefg
#for i in {0..${#parameter}};
for i in {0..7};
do
echo $i ${parameter:$i}
done
Brace expansion is performed before any other expansions, and any char‐
acters special to other expansions are preserved in the result. It is
strictly textual. Bash does not apply any syntactic interpretation to
the context of the expansion or the text between the braces.
--
Regards,
Peng
How to supply a string with space in it as parameter to a function?
Hi,
According to man bash, I thought that $@ instead of $* can help me
pass a string with space as a parameter. But it is not. Would you
please show me how to print 'b c' as a single argument in the
following code?
#!/usr/bin/env bash
function f {
#for i in $*;
for i in $@;
do
echo $i
done
}
f a 'b c' d e f g
$ ./main.sh
a
b
c
d
e
f
g
--
Regards,
Peng
Re: How to supply a string with space in it as parameter to a function?
On Wed, Jun 23, 2010 at 5:43 PM, Chris F.A. Johnson
wrote:
> On Wed, 23 Jun 2010, Peng Yu wrote:
>
>> Hi,
>>
>> According to man bash, I thought that $@ instead of $* can help me
>> pass a string with space as a parameter. But it is not. Would you
>> please show me how to print 'b c' as a single argument in the
>> following code?
>
> Always quote variable references unless you have a good reason not
> to.
>
>> #!/usr/bin/env bash
>>
>> function f {
>> #for i in $*;
>> for i in $@;
>> do
>> echo $i
>> done
>> }
>
> for i in "$@" ## note the quotes
> do
> echo "$i" ## better is: printf "%s\n" "$i"
> done
Why printf is better than echo? Is this because printf is more robust than echo?
--
Regards,
Peng
Where is the syntax of ${arr...@]:1:2} described?
Hi,
array=(a b c)
echo ${arr...@]:1:2}
I'm looking for the document for the above usage. I checked the Arrays
section of man bash, but I don't see a description of such usage. I
also searched man bash with [0-9]+:[0-9]+. But I still don't find a
description. Could anybody let me know where this is documented?
--
Regards,
Peng
Re: Where is the syntax of ${arr...@]:1:2} described?
I find the following. But this is for string according to the
highlighted word "Substring Expansion".
${parameter:offset:length}
Substring Expansion. Expands to up to length characters of
The following description is actually for array. Therefore, I suggest
to put this into the array section and add references between the two
sections.
. If
parameter is @, the result is length positional parameters
beginning at offset. If parameter is an indexed array
name sub\u2010
.
On Thu, Jul 8, 2010 at 9:27 PM, Peng Yu wrote:
> Hi,
>
> array=(a b c)
> echo ${arr...@]:1:2}
>
>
> I'm looking for the document for the above usage. I checked the Arrays
> section of man bash, but I don't see a description of such usage. I
> also searched man bash with [0-9]+:[0-9]+. But I still don't find a
> description. Could anybody let me know where this is documented?
>
> --
> Regards,
> Peng
>
--
Regards,
Peng
