Awk: Difference between revisions

Revision as of 19:29, 15 March 2006

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

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).

@@ Line 1: / Line 1: @@
-It's usually a better idea to use one command instead of using a [[pipe]] to another command, where possible. A common mistake I used to make:
+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 I was taught can be easily done all in awk:
+which can be easily done all in awk:
   # awk -F: '/root/ {print $7}' /etc/passwd
   /bin/bash
-I wanted to find out how much resident memory [[xfce4]] was using on my 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":
   $ ps auwx | awk '/xf/{print $5}'
@@ Line 19: / Line 19: @@
-I wanted to use awk to add the results together instead of doing it manually:
+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 }'
 ''N.B.'' This can be misleading in the case of programs that use large amounts of shared memory (like java).