[comp.unix.misc] Awk

ezra@daimi.aau.dk (Thomas Ravnholt) (03/07/91)

Hello !

  I have a little question about awk (nawk).

  If I want to run a unix-command in an awk-script,
how do I get the output into a variable.

  I tried

     getline < system(unixcommand)

     system(unixcommand | getline)


but it is no good of course. system returns 0 or 1 and
not the output of the unixcommand.

Hope you can answer this one.

Thanks in advance !

                   ezra@daimi.aau.dk

mek@michael.udev.cdc.com (Mark Kennedy) (03/08/91)

In article <1991Mar7.115420.21315@daimi.aau.dk>, ezra@daimi.aau.dk (Thomas Ravnholt) writes:
|> Hello !
|> 
|>   I have a little question about awk (nawk).
|> 
|>   If I want to run a unix-command in an awk-script,
|> how do I get the output into a variable.
|> 
|>   I tried
|> 
|>      getline < system(unixcommand)
|> 
|>      system(unixcommand | getline)
|> 
|> 
|> but it is no good of course. system returns 0 or 1 and
|> not the output of the unixcommand.
|> 

Crude, but effective, temporary files are your friend.  Here's a
simple example that does what you ask.

#! /bin/sh

awk '
BEGIN {
system("date > /tmp/foo")
getline X < "/tmp/foo"
print X
}'

You can use the pid if you are worried about stepping on duplicate
temp file names and insert a "trap" command to delete your temp
file(s) in case your script terminates prematurely.

     -Mark


-- 
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Mark Kennedy             ( |__  __| )  AT&T: (612) 482-2787
Control Data Corporation  \___||___/   E-Mail: mek@udev.cdc.com
			check-ins happen

steinbac@hpl-opus.hpl.hp.com (Guenter Steinbach) (03/12/91)

In comp.unix.misc, ezra@daimi.aau.dk (Thomas Ravnholt) writes:

>   I have a little question about awk (nawk).

>   If I want to run a unix-command in an awk-script,
> how do I get the output into a variable.

In nawk, I do

"unixcommand" | getline x

or even

"unixcommand" arguments_from_awk | getline x

to stuff the output of unixcommand into variable x.

Good luck.

	 Guenter Steinbach		gunter_steinbach@hplabs.hp.com