Search code examples
perlshellquoting

Using single quotes inside argument to recursive system bash call

I have a Perl script progA.pl which needs to run another Perl script progB.pl using the system command. However, progB.pl has been aliased in ~/.bashrc so I need to ensure that it is run after ~/.bashrc has been loaded. I can achieve this by using bash with the -lc option.

For this question, I simplify the problem as much as I think is needed, by considering the following version of progB.pl 

use feature qw(say);
use strict;
use warnings;
use Data::Dump qw(dd dump);

say "Received \@ARGV: " . dump @ARGV;

and here is progA.pl:

use feature qw(say);
use strict;
use warnings;

use Data::Dump qw(dd dump);

my $cmd = qq(progB.pl --opt='This option contains '"'"'single'"'"' quotes');
say "cmd = " . dump($cmd);
system( "$cmd" );
say "-----";
system( 'bash -c ' . "$cmd" );
say "-----";
system( 'bash -c ' . "'$cmd'" );
say "-----";
system( "bash -c  \"$cmd\"" );

Running 

$ progA.pl

gives output:

cmd = "progB.pl --opt='This option contains '\"'\"'single'\"'\"' quotes'"   
Received @ARGV: "--opt=This option contains 'single' quotes"  
-----   
Received @ARGV: ()  
-----   
Received @ARGV: "--opt=This"  
-----   
Received @ARGV: "--opt=This option contains single quotes"

We see that this works fine, when progB.pl is run directly without using bash -c. When I use bash -c to run the command, none of the three alternatives are working correctly.

How can I run progB.pl with an argument containing single quotes and at the same time using using bash -c ?

Solution

  • You should avoid this quoting madness at first place but if you insist, you should avoid at least one level of quoting by using system ARRAY version.

    my $cmd = q{progB.pl --opt='This option contains '"'"'single'"'"' quotes'};
system( qw(bash -c), $cmd );

    It makes it only one level of quoting madness.

    my $option = q{This option contains 'single' quotes} =~ s/'/'"'"'/gr; # '
my $cmd = qq{progB.pl --opt='$option'};
system( qw(bash -c), $cmd );

    There you can make some simple helper

    sub sq ($) { "'" . $_[0] =~ s/'/'"'"'/gr . "'" } # "

my $option = q{This option contains 'single' quotes};
my $cmd = qq{progB.pl --opt=@{[sq $option]}};
system( qw(bash -c), $cmd );