Subroutine Return Values

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

Fellow Monks, I have written a very short subroutine that executes some system calls. I want to use the values and send them to a formatted file that I have created with the reporting format within Perl, but I am not getting very far. Any help would be appreciated. The below snippet is shown below where I want to get the output from the system calls into the formatted file called FORMATTED. How can I capture the values? It seems to just run the system calls.

print FORMATTED FILE "$SECU\n";


sub _showSecInfo {
system ("$SEC","t");
system ("$SEC","s");

};
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Re: Subroutine Return Values by Zaxo (Archbishop) on Jan 12, 2007 at 01:07 UTC
To capture STDOUT of a system call, you want to use backticks ( ` ` ) or the equivalent qx. The system function only gives you the exit status. You should be checking for errors in those calls by testing `$?`. After Compline, Zaxo	[reply]
Re: Subroutine Return Values by siva kumar (Pilgrim) on Jan 12, 2007 at 04:01 UTC
The 'system' will give you only the exit status not the STDOUT. See below the difference between backticks, system call and exec. $var = `ls`; print "\n---\n $var \n---\n "; The $var will have the output of 'ls' command. [download] `$var = system('ls'); print "\n---\n $var \n---\n ";` [download] In the above code, ls command will be executed and $var will have the zero value but not the output of the 'ls' command. `$var = exec('ls'); print "\n---\n $var \n---\n ";` [download] Here ls command will get executed but $var will have nothing. More, the program will get terminated after exec execution. So I guess, you have to use backticks instead of system call.	[reply] [d/l] [select]
Re^2: Subroutine Return Values by ww (Archbishop) on Jan 12, 2007 at 16:16 UTC
This is either a nit, or ignorance, but... using AS 5.8.8 (819) on Win XP (gack, but no nx allowed at work), the last variant script in siva_kumar 's otherwise well-considered reply HANGS (as the knowledgable may well have expected). It appears that his word "program" refers to `ls` (which was replaced with `dir` for this win test) but that the statement "Here ls command will get executed but $var will have nothing." would be more precise if rephased to: "Here the ls command will be executed, but will never return control to the script. Hence, the line to print $var will never be executed." From perldoc perlfunc: `The "exec" function executes a system command and never returns-- use "system" instead of "exec" if you want it to return.`	[reply]
Re^3: Subroutine Return Values by siva kumar (Pilgrim) on Jan 18, 2007 at 07:19 UTC
Yes I agree. Thanks for comment.	[reply]