SOLVED Backticks and shell brace expansion

differenceengine has asked for the wisdom of the Perl Monks concerning the following question:

Hey there, I seek the wisdom of some monks!

Half a day spent trying to figure this out :-(, something i'm missing or don't understand properly for sure.

I want to use shell brace expansion in backticks to delete some files. Neater than doing rm a, rm b, rm c etc. The shell or Perl (not sure) always treats the { .. } literally. Anyone know how I can do this?

I've tried using qx'...', qx(...), `bash -c "..."`, and all sorts of escapes with backslashes, can't fathom it and unusually Google has not been my friend ;-)

$ touch perl.err
$ touch perl.tst
$ ls {perl.err,perl.tst}
perl.err  perl.tst
$ perl -e '`rm {perl.err,perl.tst}`';
rm: cannot remove `{perl.err,perl.tst}': No such file or directory
$ rm {perl.err,perl.tst}
$
[download]

I'm developing for FreeBSD 8 Perl 5.10 using stock /bin/sh but I observe the same behaviour on Linux with bash. Cheers.

Comment on SOLVED Backticks and shell brace expansion Download Code

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Re: Backticks and shell brace expansion by FunkyMonk (Chancellor) on Jul 31, 2011 at 20:48 UTC
You could let perl handle the deletion using unlink and glob: `unlink glob q<{perl.err,perl.tst}>; # or, glob q<perl.{err,tst}>` [download] Or, if all you want to do is delete a list of files: `unlink qw< perl.err perl.tst >;` [download]	[reply] [d/l] [select]
Re: Backticks and shell brace expansion by JavaFan (Canon) on Jul 31, 2011 at 21:30 UTC
I cannot reproduce the problem: $ touch perl.err perl.tst $ ls perl.* perl.err perl.tst $ perl -e '`rm {perl.err,perl.tst}`'; $ ls perl.* ls: perl.*: No such file or directory [download] This is on Linux and GNU bash. I think that a real Bourne shell does not have brace expansion. What happens if you do `rm {perl.err,perl.tst}` in an instance of `/bin/sh`? Or rather, what happens if you do `/bin/sh -c "rm {perl.err,perl.tst}"`?	[reply] [d/l] [select]
Re^2: Backticks and shell brace expansion by differenceengine (Novice) on Aug 01, 2011 at 20:55 UTC
Thanks for the responses! JavaFan, you have it there... on the Linux (Ubuntu) box /bin/sh is a symlink to dash which doesn't have brace expansion. I assumed /bin/sh would be a link to bash but it ain't. On the FreeBSD, I thought I was using /bin/sh but actually my user accounts are set to use tcsh. Perl always calls /bin/sh so that's why brace expansion doesn't work. On both systems Perl is not using a shell that supports it (whereas my terminal sessions are). Thankyou FunkyMonk for the unlink/glob hint. Looks like a neater, more Perl-ish way of doing what I need so I will look into it. Thanks again all.	[reply]
Re: Backticks and shell brace expansion by anonymized user 468275 (Curate) on Jul 31, 2011 at 20:50 UTC
Back ticks spawn the shell set for the unix account. That shell is trying to include the brackets and comma in the filename. One world, one people	[reply]


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