On Wed, 2010-10-27 at 15:28 -0600, Chad Perrin wrote:
> I know that in sh you can get the contents out of files specified as
> command line arguments:
>
> while read data; do
> echo $data
> done <$@
>
> I know you can also get the contents of files from pipes and redirects:
>
> while read data; do
> echo $data
> done
>
> In Perl, you can use a single construct to do both and, unlike the first
> sh example, it can also take multiple filenames as arguments and
> effectively concatenate their contents:
>
> while (<>) {
> print $_;
> }
>
> I'm not exactly an *expert* in sh, in part because when things start
> getting "interesting" while I'm writing shell scripts I tend to just use
> a more robust language like Perl. Please let me know if there's some way
> to use a simple idiom like the Perl example to get the same results in
> sh.
>
see here:
http://druidbsd.sf.net/download/sysrc.txt
For example (NOTE: this is just an example -- the function itself is
inefficient when one considers instead `tail -r file' and `tail -r <
file' and `cat file | tail -r', though the function serves as a good
example of how to achieve what you want):
# ... | lrev
# lrev $file ...
#
# Reverse lines of input. Unlike rev(1) which reverses the ordering of
# characters on a single line, this function instead reverses the line
# sequencing.
#
# For example, the following input:
#
# Line 1
# Line 2
# Line 3
#
# Becomes reversed in the following manner:
#
# Line 3
# Line 2
# Line 1
#
lrev()
{
local stdin_rev=
if [ $# -gt 0 ]; then
#
# Reverse lines from files passed as positional arguments.
#
while [ $# -gt 0 ]; do
local file="$1"
[ -f "$file" ] && lrev < "$file"
shift 1
done
else
#
# Reverse lines from standard input
#
while read -r LINE; do
stdin_rev="$LINE
$stdin_rev"
done
fi
echo -n "$stdin_rev"
}
--
Cheers,
Devin Teske
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