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Hi,

I have a weird problem with this simple bash script calling a Perl
command in a variable. I don't understand what's wrong.

$ cat test.sh

#!/bin/sh
set -x
cmd="perl -e 'print 1+2'"
$cmd

$ ./test.sh

+ cmd=perl -e 'print 1+2'
+ perl -e 'print 1+2'
Can't find string terminator "'" anywhere before EOF at -e line 1.


I also tried all sorts of variations with the quotes, but nothing seems
to work.

Thanks for any help...

In article <c8lj0q$dn9$>,
rduke15 <rduke15@hotmail__.__com> wrote:

> Hi,
>
> I have a weird problem with this simple bash script calling a Perl
> command in a variable. I don't understand what's wrong.
>
> $ cat test.sh
>
> #!/bin/sh
> set -x
> cmd="perl -e 'print 1+2'"
> $cmd
>
> $ ./test.sh
>
> + cmd=perl -e 'print 1+2'
> + perl -e 'print 1+2'
> Can't find string terminator "'" anywhere before EOF at -e line 1.
>
>
> I also tried all sorts of variations with the quotes, but nothing seems
> to work.

Try: eval $cmd

--
Barry Margolin,
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

>>$ cat test.sh
>>
>> #!/bin/sh
>> set -x
>> cmd="perl -e 'print 1+2'"
>> $cmd
>>
>>$ ./test.sh
>>
>> + cmd=perl -e 'print 1+2'
>> + perl -e 'print 1+2'
>> Can't find string terminator "'" anywhere before EOF at -e line 1.
>>
>>
>>I also tried all sorts of variations with the quotes, but nothing seems
>>to work.
>
>
> Try: eval $cmd

Yes, that works!

Thanks a lot.

Stephane CHAZELAS <> wrote in comp.lang.perl.misc:
> 2004-05-21, 15:26(-04), Barry Margolin:
> [...]
> >> cmd="perl -e 'print 1+2'"
> >> $cmd
> [...]
> > Try: eval $cmd
>
> Please get used to:
>
> eval "$cmd"

Why?

Anno

Quoth (Anno Siegel):
> Stephane CHAZELAS <> wrote in comp.lang.perl.misc:
> > 2004-05-21, 15:26(-04), Barry Margolin:
> > [...]
> > >> cmd="perl -e 'print 1+2'"
> > >> $cmd
> > [...]
> > > Try: eval $cmd
> >
> > Please get used to:
> >
> > eval "$cmd"
>
> Why?

Shell, not Perl. Presumably its more portable.

Ben

--
Every twenty-four hours about 34k children die from the effects of poverty.
Meanwhile, the latest estimate is that 2800 people died on 9/11, so it's like
that image, that ghastly, grey-billowing, double-barrelled fall, repeated
twelve times every day. Full of children. [Iain Banks]

2004-05-21, 15:26(-04), Barry Margolin:
[...]
>> cmd="perl -e 'print 1+2'"
>> $cmd
[...]
> Try: eval $cmd

Please get used to:

eval "$cmd"

--
Stephane

2004-05-24, 09:19(+00), Anno Siegel:
> Stephane CHAZELAS <> wrote in comp.lang.perl.misc:
>> 2004-05-21, 15:26(-04), Barry Margolin:
>> [...]
>> >> cmd="perl -e 'print 1+2'"
>> >> $cmd
>> [...]
>> > Try: eval $cmd
>>
>> Please get used to:
>>
>> eval "$cmd"
>
> Why?

Because, in Bourne like shells, an unquoted variable is a list
of file patterns not a string (it's fixed in zsh).

If a variable is not quoted, upon expansion, it is splitted
according to the value of the IFS special parameter, and any
wildcards are expanded.

For instance,

cmd="echo 'a b'"
eval $cmd

outputs "a b", because $cmd is splitted into "echo", "'a" and
"b'". eval concatenates those with spaces, so runs:

echo 'a b'

You would think:

cmd='echo "*"'
eval $cmd

harmless?

Try it after:

touch './""; rm -rf "$HOME"'

(DON'T!)

--
Stephane

2004-05-24, 09:31(+00), Ben Morrow:
[...]
>> > > Try: eval $cmd
>> >
>> > Please get used to:
>> >
>> > eval "$cmd"
>>
>> Why?
>
> Shell, not Perl. Presumably its more portable.

No, it's because

eval $cmd
in shell, would be the equivalent of perl's:

eval(join(" ", map(glob, split($IFS_regexp, $cmd))))

IT'S ALMOST ALWAYS WRONG TO LEAVE A VARIABLE UNQUOTED IN SHELL
SCRIPTS.

--
Stephane