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Old 07-23-2006, 09:39 PM   #1
drkstr
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perl: send output of system() call to variable


I am writing a perl script that uses system("fdisk -l") and I want to send the output to a variable in the script instead of STDOUT. I have a perl book which says you can send the output to a file, will I have to send it to a file then read it into a variable, or is there an easier way to do this?

Thanks for your time!
...drkstr
 
Old 07-23-2006, 09:54 PM   #2
taylor_venable
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You're looking for the "open()" command here, which can be used to open streams to processes as well as normal files. Instead of using "<" or ">" to indicate what direction to open a stream (for input or output), use "-|" to read from a process or "|-" to write to it. In place of the filename, just provide the program to execute. In your case:
Code:
open($fh, "-|", "fdisk -l")
And then just read from the $fh filehandle like you normally would. You can even slurp it all up into a variable if you want.

An easier, but less flexible, alternative is the "readpipe()" command. It takes a single scalar parameter - the program to execute. In scalar context it returns a single, possibly multiline string with all the output of that program. In list context it returns a list of strings, each one line from the program's output. Again, in your example:
Code:
my $output = readpipe("fdisk -l")

Last edited by taylor_venable; 07-23-2006 at 09:59 PM.
 
Old 07-23-2006, 10:07 PM   #3
xhi
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backticks should work also

Code:
$output = `fdisk -l`;
 
Old 07-23-2006, 10:16 PM   #4
taylor_venable
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True, they do; as does the qx quotation method.
Code:
$output = qx(fdisk -l)
But an important distinction is that backticks and qx both do variable interpolation in the command, while using open() or readpipe() leaves that choice more explicitly up to the user.
 
Old 07-23-2006, 10:47 PM   #5
drkstr
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Quote:
to indicate what direction to open a stream (for input or output), use "-|" to read from a process or "|-" to write to it.
Thanks for the quick reply. That did the trick. I thought I had to use a file descriptor to redirect the output but I couldn't quite figure out how to put it together.

best regards,
...drkstr
 
  


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