I am appending a value 100 to every line in a file with the code below. This code works well when I run it in terminal but when I save the code in .awk file and run it I am getting an error. How to run this code from a script file instead of running from terminal?

code:  awk -F ';' '{if ($2==NULL) print $0"100"}' example.txt


awk -F ';' '{if ($2==NULL) print $0"100"}'

command in terminal

awk -f my.awk example.txt


 invalid char ''' in expression. I get this error at ';'

How to rectify this error and run the awk file on example.txt?


When executing an awk script with awk -f, the script should only contain the awk code.

In your case

{if ($2==NULL) print $0"100"}


$2 == NULL { print $0 "100" }

You would execute this with

awk -F ';' -f my.awk example.txt

If you want to set FS to ; in the script (statically, instead of on the command line with -F), do so in a BEGIN block:

BEGIN { FS = ";" }

$2 == NULL { print $0 "100" }

Note, too, that the variable NULL is unset in your code.

  • Ok. Got it. Thanks. What is meant by NULL is unset? I did not understand that line. – Laxman Apr 11 at 11:44
  • @Laxman You are using a variable called NULL that you haven't given any value. If you want to test whether $2 is empty, just use $2 == "". – Kusalananda Apr 11 at 11:49

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