System Calls

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

Hello,

A quick and easy one - is it possible to tell whether a system call has been executed properly?

I have the following which does not appear to create a directory, nor give the error message:

system ("mkdir($NEW_AGENDA_ROOT,0777)") || die(" Failed to create directory $NEW_AGENDA_ROOT.");

Any ideas?

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Re: System Calls by broquaint (Abbot) on Jul 07, 2003 at 09:16 UTC
General convention to indicate whether a program has exited successfully or not is the exit status of the program. If the exit status is equal to 0 then it was successful, otherwise a failure e.g `system("some_program --and arguments") == 0 or die("Couldn't do something with stuff");` [download] Although in your case it looks like `mkdir` would be the better option. See. `system` for more info on the exit status of programs (which lives in the `$?` variable). HTH `_________ broquaint`	[reply] [d/l]
Re: System Calls by choocroot (Friar) on Jul 07, 2003 at 09:39 UTC
Hum ... do you want to call the system command "`mkdir`" ? or use the Perl function "`mkdir()`" ? your example seems to mix the call to the mkdir system command with the use of the mkdir function ... If you want to call the system command `/bin/mkdir` with `system()` : `system( "mkdir", $NEW_AGENDA_ROOT ) == 0 or die( "Failed to create dir +ectory $NEW_AGENDA_ROOT." );` [download] (see "`perldoc -f system`" for explanation on this construction) If you want to use the `mkdir()` function then : `mkdir($NEW_AGENDA_ROOT, 0777) or die( "Failed to create directory $NEW +_AGENDA_ROOT: $!" );` [download] (see "`perldoc -f mkdir`" for the mkdir function help) By the way, you should use this mkdir() Perl function. It's the prefered way to make a directory from perl, as it's a builtin function available on all platform, and is much more secure than the use of a system call. update: Removed the final "0777" argument on the system() call for the mkdir command as it won't set the access mode but simply create the directory "`0777`". (If you wants to set the access rights you can use the mkdir "`--mode` " switch). Thank you grantm for pointing me on this error.	[reply] [d/l] [select]
Re: System Calls by ant9000 (Monk) on Jul 07, 2003 at 09:34 UTC
The correct answer (ie, check `$?`) has been already given, so this is just out of curiosity... what was `system ("mkdir($NEW_AGENDA_ROOT,0777)")` supposed to do? Inside `system` you have to put system commands, not Perl functions!	[reply] [d/l] [select]