Getting the return value of a command executed using backticks in Perl

Question

I can do the following in bash:

output=`command`
retcode=$?

Is there any way to do the same in Perl? Something like this:

$output=`command`
$retcode=???

Marozas

Answer 1

You can read the $? variable (as in the shell). From man perlvar

 $?      The status returned by the last pipe close, backtick ("``") command, successful call to wait() or waitpid(), or from the
               system() operator.  This is just the 16-bit status word returned by the traditional Unix wait() system call (or else is made up
               to look like it).  Thus, the exit value of the subprocess is really ("$? >> 8"), and "$? & 127" gives which signal, if any, the
               process died from, and "$? & 128" reports whether there was a core dump.  (Mnemonic: similar to sh and ksh.)

               Additionally, if the "h_errno" variable is supported in C, its value is returned via $? if any "gethost*()" function fails.

               If you have installed a signal handler for "SIGCHLD", the value of $? will usually be wrong outside that handler.

               Inside an "END" subroutine $? contains the value that is going to be given to "exit()".  You can modify $? in an "END"
               subroutine to change the exit status of your program.  For example:

                   END {
                       $? = 1 if $? == 255;  # die would make it 255
                   }

               Under VMS, the pragma "use vmsish 'status'" makes $? reflect the actual VMS exit status, instead of the default emulation of
               POSIX status; see "$?" in perlvms for details.

               Also see "Error Indicators".

Flunk

Answer 2

And since Perl 5.10, you also have ${^CHILD_ERROR_NATIVE}.

From http://perldoc.perl.org/perl5100delta.html#New-internal-variables :

${^CHILD_ERROR_NATIVE}

This variable gives the native status returned by the last pipe close, backtick command, successful call to wait() or waitpid(), or from the system() operator. See perlvar for details.

Diphyllous

Answer 3

For me this works:

$output=`command`
$retcode=$? >> 8

For some reason, I have to shift-right the value, for 8 bits.

Theta