Perl backticks using bash-CodePudding

In Perl, the default shell to execute backticks is sh. I'd like to switch to use bash for its richer syntax. So far I found that the suggested solution is

`bash -c \"echo a b\"`

The apparent drawback is that the escaped double quotes, which means I will have difficulty to use double quotes in my bash args. For example, if I wanted to run commands requiring double quotes in bash

echo "a'b"

The above method will be very awkward.

Perl's system() call has a solution for this problem: to use ARRAY args,

system("bash", "-c", qq(echo "a'b"));

This keeps my original bash command unmodified, and almost always.

I'd like to use ARRAY args in backticks too. Is it possible? Thank you for your advice

CodePudding user response：

You can use single quotes as delimiter with qx like this:

my $out = qx'bash -c "echo a b"';

this will according to perlop protect the command from Perl's double-quote interpolation.

Unfortunately, this does not work for single quotes. If you want to do echo "'" for example, you need the following:

my $out = `bash -c \"echo \\\"'\\\"\"`;

Edit:

To help you managing the escaping of quotes you could use a helper function like this:

use experimental qw(signatures);
sub bash_backticks($code) {
    $code =~ s/'/'"'"'/g;
    `bash -c '$code'`
}

CodePudding user response：

I have the following sub that works

    sub bash_output {
       my ($cmd) = @_; 
    
       open my $ifh, "-|", "bash", "-c", $cmd or die "cannot open file handler: $!";
    
       my $output = ""; 
       while (<$ifh>) {
          $output .= $_; 
       }   
    
       close $ifh;
    
       return $output;
    }

    print "test bash_output()\n";

    my @strings = (
         qq(echo "a'b"),
         'echo $BASH_VERSION',
         '[[ "abcde" =~ bcd ]] && echo matched',
         'i=1; ((i  )); echo $i',
   );

   for my $s (@strings) {
         print "bash_output($s) = ", bash_output($s), "\n";
   }

The output is

bash_output(echo "a'b") = a'b

bash_output(echo $BASH_VERSION) = 4.4.20(1)-release

bash_output([[ "abcde" =~ bcd ]] && echo matched) = matched

bash_output(i=1; ((i  )); echo $i) = 2

My answer is long-winded but it fills my need. I was hoping Perl has a built-in solution just like how it handles system() call and I am still hoping.

CodePudding user response：

You can change the shell used by perl :

$ENV{PERL5SHELL} = "bash";
my $out = qx{echo "Hello ' world from bash \$BASH_VERSION"};
print($out);