How to check if the variable value in AWK script is null or empty?

Question

1. I am using AWK script to process some logs.
2. At one place I need to check if the variable value is null or empty to make some decision.

Any Idea how to achieve the same?

awk '  {     {        split($i, keyVal, "@")        key=keyVal[1];        val=keyVal[2];        if(val ~ /^ *$/)        val="Y";      }  }  ' File 

I have tried with

1) if(val == "")  2) if(val ~ /^ *$/) 

not working in both cases.

Answer 1

The comparison with "" should have worked, so that's a bit odd

As one more alternative, you could use the length() function, if zero, your variable is null/empty. E.g.,

if (length(val) == 0) 

Also, perhaps the built-in variable NF (number of fields) could come in handy? Since we don't have access to your input data it's hard to say though, but another possibility.

Answer 2

You can directly use the variable without comparison, an empty/null/zero value is considered false, everything else is true.

See here :

# setting default tag if not provided if (! tag) {         tag="default-tag" } 

So this script will have the variable tag with the value default-tag except if the user call it like this :

$ awk -v tag=custom-tag -f script.awk targetFile 

This is true as of : GNU Awk 4.1.3, API: 1.1 (GNU MPFR 3.1.4, GNU MP 6.1.0)