Does exactly the same thing asexec 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 -c on Unix platforms, but varies on other platforms). If there are no shell metacharacters in the argument, it is split into words and passed directly toexecvp, 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 (seeperlport). To be safe, you may need to set$| ($AUTOFLUSH in English) or call theautoflush() method ofIO::Handle on any open handles.
The return value is the exit status of the program as returned by thewait call. To get the actual exit value shift right by eight (see below). See also"exec". This isnot what you want to use to capture the output from a command, for that you should use merely backticks orqx//, as described in"`STRING`" in perlop. Return value of -1 indicates a failure to start the program (inspect $! for the reason).
Likeexec,system allows you to lie to a program about its name if you use thesystem PROGRAM LIST syntax. Again, see"exec".
Becausesystem and backticks blockSIGINT andSIGQUIT, killing the program they're running doesn't actually interrupt your program.
@args = ("command", "arg1", "arg2"); system(@args) == 0 or die "system @args failed: $?"You can check all the failure possibilities by inspecting$? like this:
if ($? == -1) {print "failed to execute: $!\n"; } elsif ($? & 127) {printf "child died with signal %d, %s coredump\n", ($? & 127), ($? & 128) ? 'with' : 'without'; } else {printf "child exited with value %d\n", $? >> 8; }or more portably by using the W*() calls of the POSIX extension; seeperlport for more information.
When the arguments get executed via the system shell, results and return codes will be subject to its quirks and capabilities. See"`STRING`" in perlop and"exec" for details.
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