NAME

IPC::ReadpipeX - List form of readpipe/qx/backticks for capturing output

SYNOPSIS

  use IPC::ReadpipeX;

  my $path = '/file path/with$shell/characters&';
  my @entries = readpipex 'ls', '-l', $path;
  if ($?) {
    my $exit = $? >> 8;
    die "ls '$path' exited with status $exit";
  }

  my $hostname = readpipex 'hostname', '-f';
  chomp $hostname;

DESCRIPTION

The built-in readpipe function, also known as the qx operator or backticks (``), runs a command and captures the output (STDOUT). However, unlike system and exec, the command will always be parsed by the shell, and it does not provide a list form to bypass shell parsing when multiple arguments are passed. "readpipex" provides this capability in a simple copy-pastable function.

For other methods of redirecting output, capturing STDERR, and interacting with the process, consider the modules listed in "SEE ALSO".

FUNCTIONS

readpipex is exported by default.

readpipex

  my $output = readpipex $cmd, @args;
  my @output = readpipex $cmd, @args;

Runs the given command, capturing STDOUT and returning it as a single string in scalar context, or an array of lines in list context. If more than one argument is passed, the command will be executed directly rather than via the shell, as in system and exec. The command and each argument will be passed directly to the execvp(3) system call, so the program will receive the arguments exactly as passed, without first interpreting shell metacharacters.

Errors forking or running the command will raise an exception, and $! will be set to the error code. The exit status of the process is otherwise available in $? as normal.

The code of this function can easily be copy-pasted and is shown below.

  sub readpipex {
    no warnings 'exec';
    open my $stdout, '-|', @_ or die "readpipex '$_[0]' failed: $!";
    my @output = wantarray ? readline($stdout)
      : do { local $/; scalar readline $stdout };
    close $stdout;
    return wantarray ? @output : $output[0];
  }

The above code snippet may be considered to be licensed under The Unlicense for the purpose of copying without attribution or warranty.

CAVEATS

  • Behavior when passing no arguments is unspecified.

  • The shell can still be invoked if only one argument is passed.

  • The -| open mode requires Perl 5.8 or newer on a system that supports forking, or Perl 5.22 or newer on Windows.

  • Errors while reading or closing the pipe, though exceedingly rare, are ignored, as in the core readpipe.

BUGS

Report any issues on the public bugtracker.

AUTHOR

Dan Book <dbook@cpan.org>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2019 by Dan Book.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

SEE ALSO

  • IPC::System::Simple - provides system and capture functions with optional exit status checking and variants that always bypass the shell

  • IPC::Run3 - run a process and direct STDIN, STDOUT, and STDERR

  • Capture::Tiny - capture STDOUT and STDERR in any wrapped code

  • IO::Async::Process - complete asynchronous control over a process and its handles