I've written a feature I find useful for bash that escapes a single ampersand
if it is surrounded on both sides by any non-blank or non-meta characters. This
logic is toggled by a set option, "compressedand" that can be enabled with `set
[-|+]c` or `set -o compressedand`.
As an example:
$ echo this&echo that
[1] 32324
that
this
[1]+ Doneecho this
$ set -c
$ echo this&echo that
this&echo that
Handling of multi-character metas, such as &>, |&, &&, et al, is still parsed
by BASH and their functions remain unaffected.
$ echo this& echo that
[1] 1373
that
this
[1]+ Doneecho this
$ echo this &echo that
[1] 1375
that
this
[1]+ Doneecho this
$ echo this&&echo that
this
that
$ ps ax&>/tmp/ps&echo
$ ls /tmp/ps\&echo
/tmp/ps&echo
The primary use case for the option is to ease using unquoted URLs as arguments
that have multiple query parameters. Yes, quoting the URL precludes the need
for this feature, but I forget sometimes (okay, too often):
$ set +c
$ echo https://example.com/inputs?v=22&time=now&cp=key
[1] 32335
[2] 32336
https://example.com/inputs?v=22
[1]- Doneecho https://example.com/inputs?v=22
[2]+ Donetime=now
$ set -c
$ echo https://example.com/inputs?v=22&time=now&cp=key
https://example.com/inputs?v=22&time=now&cp=key
I've attached a patch that was written against bash-4.4 and tested to work
against the most recent DEVEL commit (3235014e5b) as of 04/22. The patch
provides the logic, set option control, and updates to the man and info pages.
I'm still working on getting some tests worked up. I wanted to get this
submitted to get a feel for general likeability and for input on things I need
to do for a proper contribution.
And, for completeness, here are the bash VERSIONs I've tested this on:
GNU bash, version 4.4.23(1)-release (x86_64-pc-linux-gnu)
GNU bash, version 5.0.16(1)-maint (x86_64-pc-linux-gnu)
I haven't looked up to see what POSIX has to say about this, but I'm fairly
confident that this flies in the face of it. If that's the case and this patch
is dismissed accordingly, I'll accept that. This was a fun exercise anyway. .)
- Eric.
---
Fudd's First Law of Opposition:
"If you push something hard enough, it will fall over."
- Firesign Theater
diff --git a/builtins/set.def b/builtins/set.def
index 8122361..2467e73 100644
--- a/builtins/set.def
+++ b/builtins/set.def
@@ -59,7 +59,7 @@ extern int no_line_editing;
$BUILTIN set
$FUNCTION set_builtin
-$SHORT_DOC set [-abefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
+$SHORT_DOC set [-abcefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
Set or unset values of shell options and positional parameters.
Change the value of shell attributes and positional parameters, or
@@ -68,6 +68,7 @@ display the names and values of shell variables.
Options:
-a Mark variables which are modified or created for export.
-b Notify of job termination immediately.
+ -c Escape a single ampersand surrounded by non-blank/non-meta text.
-e Exit immediately if a command exits with a non-zero status.
-f Disable file name generation (globbing).
-h Remember the location of commands as they are looked up.
@@ -77,50 +78,51 @@ Options:
-n Read commands but do not execute them.
-o option-name
Set the variable corresponding to option-name:
- allexportsame as -a
- braceexpand same as -B
+ allexport same as -a
+ braceexpandsame as -B
+ compressedand same as -c
#if defined (READLINE)
- emacsuse an emacs-style line editing interface
+ emacs use an emacs-style line editing interface
#endif /* READLINE */
- errexit same as -e
- errtrace same as -E
- functracesame as -T
- hashall same as -h
+ errexitsame as -e
+ errtrace same as -E
+ functrace same as -T
+ hashallsame as -h
#if defined (BANG_HISTORY)
- histexpand same as -H
+ histexpand same as -H
#endif /* BANG_HISTORY */
#if defined (HISTORY)
- history enable command history
+ historyenable command history
#endif
- ignoreeofthe shell will not exit upon reading EOF
+ ignoreeof the shell will not exit upon reading EOF
interactive-comments
- allow comments to appear in interactive commands
- keyword same as -k
+ allow comments to appear in interactive commands
+ keywordsame as -k
#if defined (JOB_CONTROL)
- monitor same as -m
+ monitorsame as -m
#endif
- noclobbersame as -C
- noexec sam
