Capture output of system() function

[jbhis8up]

I'm trying to write a script that will write the output of a system("<some command>") function to a text file, however, the file that gets written has 0 bytes. Please help.

-Josh

 

[MikeLacey]

Josh,

make sure you capture both STDOUT and STDERR, like this

system('some_command > file.out 2>&1');

Mike

"Deliver me from the bane of civilised life; teddy bear envy."

Want to get great answers to your Tek-Tips questions? Have a look at faq219-2884

 

[rharsh]

Or if you want to do any processing of the results before they get printed to the file, you can do:

my $results = `some_command`;
open OUTPUT, "> somefile.txt";
print OUTPUT $results;
close OUTPUT;

Those symbols around some_command are actually backticks, the apostrophe-looking symbol that's on the key with the ~ (tilde) symbol.

 

[EBGreen]

Or
my (@results) = `some_command`;

Then process the array to do whatever you need to do with the output.

[blue]"Well, once again my friend, we find that science is a two headed beast. One head is nice, it gives us aspirin and other modern conveniences,...but the other head of science is BAD! Oh, beware the other head of science, Arthur; it bites!!" - The Tick[/blue]

 

[MikeLacey]

rharsh and Tom are both right - as usual with Perl there's more than twelve ways to do most things. You still have to use the 2>&1 trick to capture *all* the output from an external program/script though.

Mike

"Deliver me from the bane of civilised life; teddy bear envy."

Want to get great answers to your Tek-Tips questions? Have a look at faq219-2884

 

[jbhis8up]

Something else about the script I was trying to write is that I want perl to perform actions against a file I specify on the command line. Basically I type "perl script.pl <filename>" to run the script agains that file. One of the commands I run against this file does not produce output to the screen but when I run the command by itself on the command line and then redirect the output to a file (exapmle: "command > output.txt") the file is populated. I'm trying to do the same thing from within perl. I appreciate the help. Thanks.

-Josh

 

[jbhis8up]

As far as capturing the output, does it matter if I'm on a Win32 platform (which I am) as opposed to a UNIX flavor operating system? I've seen the "2>&1" when writing scripts in UNIX, but I've never seen that used on a Windows platform.

 

[MikeLacey]

Good point there And I had to go check it as well - but yes, it does seem to work as per UNIX. (Perl 5.8.1 and WinXP here)

The script I tested this with is

system('dir mike.pl >cmd.out 2>&1');

which produced output of:

C:\Perl>type cmd.out
Volume in drive C has no label.
Volume Serial Number is F8B2-3FC8

Directory of C:\Perl

File Not Found

Without the 2>&1 the line File Not Found is missing.

Mike

"Deliver me from the bane of civilised life; teddy bear envy."

Want to get great answers to your Tek-Tips questions? Have a look at faq219-2884