FS - The Input Field Separator Variable in Awk

AWK can be used to parse many system administration files. However, many of these files do not have whitespace as a separator. as an example, the password file uses colons. You can easily change the field separator character to be a colon using the "-F" command line option. The following command will print out accounts that don't have passwords:

awk -F: '{if ($2 == "") print $1 ": no password!"}'

There is a way to do this without the command line option. The variable "FS" can be set like any variable, and has the same function as the "-F" command line option. The following is a script that has the same function as the one above.

#!/bin/awk -f
BEGIN {
 FS=":";
}
{
 if ( $2 == "" ) {
  print $1 ": no password!";
 }
}