Perl 5 version 8.0 documentation
- system LIST
- system PROGRAM LIST
Does exactly the same thing as
exec LIST, except that a fork is done first, and the parent process waits for the child process to complete. Note that argument processing varies depending on the number of arguments. If there is more than one argument in LIST, or if LIST is an array with more than one value, starts the program given by the first element of the list with arguments given by the rest of the list. If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing (this is
/bin/sh -con Unix platforms, but varies on other platforms). If there are no shell metacharacters in the argument, it is split into words and passed directly to
execvp, which is more efficient.
Beginning with v5.6.0, Perl will attempt to flush all files opened for output before any operation that may do a fork, but this may not be supported on some platforms (see perlport). To be safe, you may need to set
$|($AUTOFLUSH in English) or call the
IO::Handleon any open handles.
The return value is the exit status of the program as returned by the
waitcall. To get the actual exit value shift right by eight (see below). See also exec. This is not what you want to use to capture the output from a command, for that you should use merely backticks or
qx//, as described in `STRING` in perlop. Return value of -1 indicates a failure to start the program (inspect $! for the reason).
systemand backticks block
SIGQUIT, killing the program they're running doesn't actually interrupt your program.
You can check all the failure possibilities by inspecting
- $exit_value = $? >> 8;
- $signal_num = $? & 127;
- $dumped_core = $? & 128;
or more portably by using the W*() calls of the POSIX extension; see perlport for more information.