Error using back tick operators if it has special perl chars in it

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

I am getting an error when passing $INVALID_STRING as a parameter to a java program which is executed through the back tick operator.

$INVALID_STRING="!"$\%&'()*/@`~";
$STRING_TO_EXECUTE="java myprogram -opt1 ABC -opt2 $INVALID_STRING";
@output=`$STRING_TO_EXECUTE 2>&1`;
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On executing my Perl Script I get the following error:

sh: -c: line 1: unexpected EOF while looking for matching ``'
sh: -c: line 3: syntax error: unexpected end of file
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I tried removing the character ` and ' out of the $INVALID STRING, but it still complains with similar error. Can anyone help solve this problem ? Thanks in advance.

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Re: Error using back tick operators if it has special perl chars in it by japhy (Canon) on Jul 28, 2004 at 19:29 UTC
First of all, the code you've given us shouldn't even compile as Perl. I would suggest the following: $INVALID_STRING = quotemeta q<!"$\%&'()/@`~>; $STRING_TO_EXECUTE = "java myprogram -opt1 ABC -opt2 $INVALID_STRING"; [download] Or, better yet, use open() instead. _____________________________________________________ Jeff `japhy` Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and `perl` hacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart*	[reply] [d/l]
Re: Error using back tick operators if it has special perl chars in it by gaal (Parson) on Jul 28, 2004 at 19:36 UTC
Your problem is only partly that the string contains special Perl characters. 1. When you assign to $INVALID_STRING, make sure you protect yourself from interpolation. '"!"' etc. just don't end up in your variable. In this case, you can use the generic single quote op `q`: $INVALID_STRING = q{!"$\%&'()/@`~}; Here { ... } act as the delimiters, but many other options are available. See perlop for details. 2. Your main problem is that the shell* is having a hard time dealing with the string, not perl. This is your main problem because it's harder to solve :-) I'm afraid that this will depend a bit on which shell your system uses; experiment a bit with escaping ! and ' and putting everything in single quotes.	[reply] [d/l] [select]
Re: Error using back tick operators if it has special perl chars in it by revdiablo (Prior) on Jul 28, 2004 at 22:26 UTC
To expand a bit on japhy's response, you will be best served by using a piping form of open, with the parameters in list form. Using list form will prevent any shell expansion on the parameters, which avoids many problems. Here's a very simple example: `open my $lsfh, "-\|", "ls", "-l" or die "Cannot open pipe from 'ls': $!"; while (<$lsfh>) { print; } close $lsfh;` [download]	[reply] [d/l]