Awk: Difference between revisions
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== Awk and /etc/passwd == | |||
It's usually a better idea to use one command instead of using a [[pipe]] to another command, where possible. A common mistake: | It's usually a better idea to use one command instead of using a [[pipe]] to another command, where possible. A common mistake: | ||
# grep root /etc/passwd | awk -F: '{print $7}' | # grep root /etc/passwd | awk -F: '{print $7}' | ||
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/bin/bash | /bin/bash | ||
== Awk and ps == | |||
Say you wanted to find out how much resident memory [[xfce4]] was using on your system, and it appears most xfce applications start with "xf": | Say you wanted to find out how much resident memory [[xfce4]] was using on your system, and it appears most xfce applications start with "xf": | ||
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''N.B.'' This can be misleading in the case of programs that use large amounts of shared memory (like java). | ''N.B.'' This can be misleading in the case of programs that use large amounts of shared memory (like java). | ||
== Awk and multi-row documents == | |||
pretend you have a file that has IP numbers where multiple can be on one row and you need to | |||
flatten these into 1 per row here is how the solution looks like: | |||
francisco$ cat ipfile | |||
192.168.0.1 | |||
192.168.0.2 192.168.0.3 | |||
10.0.0.1 10.0.0.2 10.0.0.3 | |||
francisco$ awk '{ for (i = 1; i <= NF ; i++) print $i; }' ipfile | |||
192.168.0.1 | |||
192.168.0.2 | |||
192.168.0.3 | |||
10.0.0.1 | |||
10.0.0.2 | |||
10.0.0.3 | |||
Revision as of 03:50, 2 July 2008
Awk and /etc/passwd
It's usually a better idea to use one command instead of using a pipe to another command, where possible. A common mistake:
# grep root /etc/passwd | awk -F: '{print $7}'
/bin/bash
which can be easily done all in awk:
# awk -F: '/root/ {print $7}' /etc/passwd
/bin/bash
Awk and ps
Say you wanted to find out how much resident memory xfce4 was using on your system, and it appears most xfce applications start with "xf":
$ ps auwx | awk '/xf/{print $5}'
15924
14668
11948
11764
12944
16264
1860
If you wanted to use awk to add the results together instead of doing it manually:
$ ps auwx | awk '/xf/{ tot += $5 } END { print tot }'
69108
N.B. This can be misleading in the case of programs that use large amounts of shared memory (like java).
Awk and multi-row documents
pretend you have a file that has IP numbers where multiple can be on one row and you need to flatten these into 1 per row here is how the solution looks like:
francisco$ cat ipfile 192.168.0.1 192.168.0.2 192.168.0.3 10.0.0.1 10.0.0.2 10.0.0.3
francisco$ awk '{ for (i = 1; i <= NF ; i++) print $i; }' ipfile
192.168.0.1
192.168.0.2
192.168.0.3
10.0.0.1
10.0.0.2
10.0.0.3
