为什么 IPC::System::Simple(capture) 不适用于 arguments

Question

I am trying to call a second script from the main script. When I am passing the argument in the command itself using capture, it's working. But when I am trying to send the command and arguments separately in capture function it's giving me an error that it can't find the specified file.

Second script

#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

my $word= $ARGV[0];

my $crpyt = "$word crypted";
print "$crpyt\n";

my $decrypt = "$word decrypted";
print "$decrypt\n";

main.pl

#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

use IPC::System::Simple qw(capture capturex);

my $cmd= 'perl xyz.pl Hello';
my @arr = capture($cmd);

print "$arr[0]";
print "$arr[1]\n";

This is working Output:

Hello crypted
Hello decrypted

BUT main.pl

#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

use IPC::System::Simple qw(capture capturex);

my $cmd= 'perl xyz.pl';
my @arg=("Hello");
my @arr = capture($cmd,@arg);

print "$arr[0]";
print "$arr[1]\n";

This is not working. It says "perl xyz.pl" failed to start: "The system cannot find the file specified" at main.pl line 11

Answer 1

If you only pass a single scalar, capture expects it to be a shell command.

As such, capture('perl xyz.pl Hello') works.

If you pass multiple scalars, capture expects the first to be a path to a program to execute. The rest are passed as arguments.

As such, capture('perl xyz.pl', 'Hello') doesn't work.

---

You could use

use IPC::System::Simple qw( capture );

my @cmd = ( 'perl', 'xyz.pl', 'Hello' );
capture(@cmd)

But you never want to use capture unless you pass a single scalar that's a shell command. Use capturex when passing a path and arguments.

use IPC::System::Simple qw( capturex );

my @cmd = ( 'perl', 'xyz.pl', 'Hello' );
capturex(@cmd)

---

But let's say you get the string perl xyz.pl from elsewhere. A shell needs to be invoked, so we need to convert the arguments in to shell literals.

use IPC::System::Simple qw( capture );
use String::ShellQuote  qw( shell_quote );

my $cmd = 'perl xyz.pl';
my @extra_args = 'Hello';
my $full_cmd = $cmd . ' ' . shell_quote(@extra_args);
capture($cmd)

Alternatively,

use IPC::System::Simple qw( capturex );

my $cmd = 'perl xyz.pl';
my @extra_args = 'Hello';
capturex('sh', '-c', 'eval $0 "$@"', $cmd, @extra_args)