running programs

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

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Re: running programs by melguin (Pilgrim) on Aug 28, 2001 at 23:07 UTC
There are arguments all around this issue, but I won't go into those. `system('what ever you want to run');` [download] or you can try print `what ever you want to run`; ##these are backticks [download] Hope that helps. melguin.	[reply] [d/l] [select]
Re: running programs by arturo (Vicar) on Aug 28, 2001 at 23:08 UTC
Take a look at the man pages for `system` and backticks `` Backticks are useful if you want to capture the output of the external program. my $output = `/home/mailman/bin/add_members -n/home/mailman/lists/minl +ist-news/email.out -wy minlist-news` or die "Cant' add members: $!\n" +; [download] The `or die` part is important -- it will be called if something goes wrong with the external program. An alternative to backticks is `system`, just `system "command"`, which is more useful when you don't need to capture the output and/or when you want more security (it's dangerous to put user input into any call that's going to get executed on your system). HTH! `perl -e 'print "How sweet does a rose smell? "; chomp ($n = <STDIN>); +$rose = "smells sweet to degree $n"; other_name = rose; print "$oth +er_name\n"'` [download]	[reply] [d/l] [select]
Re: running programs by jlongino (Parson) on Aug 28, 2001 at 23:40 UTC
As already mentioned, you probably want to use the `system` command. I would add that you should also use the form: `my $rc = system "some command"; if ($rc != $whatever_return_code_you_expect) { # do some debugging stuff }` [download] to take advantage of whatever error codes/messages that may be returned. If the code and the comments disagree, then both* are probably wrong.* -- Norm Schryer	[reply] [d/l] [select]
Re: running programs by derby (Abbot) on Aug 28, 2001 at 23:47 UTC
Or if you wanted to use exec you need to break your command into a list: `exec '/home/mailmain/bin/add_members', '-n/home/mailmain/lists/minlist +-news/email.out', '-wy', 'minlist-news'` [download] or more realistically with options: `exec '/home/mailmain/bin/add_members', '-n', '/home/mailmain/lists/min +list-news/email.out', '-wy', 'minlist-news'` [download] But the thing to remember about exec, it replaces the current running process, nothing in your script after the exec call will ever be executed. That's why you normally see the `fork/exec` model being used. `fork` will create another (child) process and the `exec` will replace the child - leaving the parent to either wait for the child and continue or just continue. -derby Update Well it doesn't automatically replace the child, it can replace the parent. It's up to you on which one it replaces.	[reply] [d/l] [select]
Re: running programs by RayRay459 (Pilgrim) on Aug 29, 2001 at 01:12 UTC
For a quick answer try system("your command or something"); You can also look at the man page on system or do a search on cpan. (search.cpan.org). Secondly, being somewhat new to perl myself(a couple of months), you should pick up O'Reilly's book "Learning Perl". I was able to learn from it very fast and it teaches you how to start writing meaningful scripts and all of the basics. Good luck and happy hunting. Ray	[reply]
Re: running programs by Hofmator (Curate) on Aug 29, 2001 at 14:15 UTC
Ok, to make the set complete, I mention the solution using open: `open (CMD, "your command \|") or die "Couldn't fork: $!"; while (my $line = <CMD>) { # read output from command linewise } # or slurp the whole output into one string # { # local $/; # $string = <CMD>; # } # or read the output into an array for easy line access # my @lines = <CMD>; close CMD;` [download] -- Hofmator	[reply] [d/l]