Response from system or Exec

engtech has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Response from system or Exec by sauoq (Abbot) on Nov 03, 2003 at 07:24 UTC
I think I read somewhere that I can get a response from that command as well like a boolean or error level... If the return value of `system()` is positive, it contains the return value of the command you called and some other information. This is also available via the special variable `$?`. This is how you can get at that information (straight out of the docs): `$exit_value = $? >> 8; $signal_num = $? & 127; $dumped_core = $? & 128;` [download] If `system()` returns a `-1`, that means it couldn't start the program at all. In which case, it will give you the reason in the `$!` special variable. Could anyone point me in the right direction??? Sure... `perldoc -f system` -sauoq "My two cents aren't worth a dime.";	[reply] [d/l]
•Re: Response from system or Exec by merlyn (Sage) on Nov 03, 2003 at 11:55 UTC
Aside from the other posts in this thread, I'd also like to point out that: `system("sstty +rs 1a12","/");` [download] is very unlikely to work, unless you have a command called "sstty +rs 1a12", and you want to pass it the single argument of "/". When you invoke the multi-arg system or exec or pipe-open, you assume complete responsibility for argument parsing, since no shell will decide that for you. The first argument will be precisely the command name (as found in the $ENV{PATH}, of course), and the remaining args are passed one-by-one (although a NUL character cannot be passed because of the underlying interfaces). Perhaps what you wanted was: `system("sstty","+rs","1a12","/")` [download] -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l] [select]
Re: Response from system or Exec by arthas (Hermit) on Nov 03, 2003 at 08:51 UTC
Just an addition, since you're mentioning `exec()` in the subject of your question. While `system()` returns a value, be aware that `exec()` never returns, but replaces your program with the one you are calling using `exec()`. Michele.	[reply] [d/l] [select]
Re: Response from system or Exec by Abigail-II (Bishop) on Nov 03, 2003 at 09:59 UTC
Actually, exec might return, if 1) perl doesn't need to call the shell to execute the command (that is, exec is either given more than one argument, or a string which has no characters (except whitespace) that are special to the shell), and hence will call `execvp` directly, and 2) the command can't be called (usually because the file doesn't exists, or due to permission problems). See `perldoc -f exec`. Abigail	[reply]