include library of functions in awk

Question

There are many common functions (especially arithmetic/mathematics) that are not built into awk that I need to write myself all the time.

For example:

1. There is no c=min(a,b) , so in awk i constantly write c=a<b?a:b
2. same for maximum i.e. c=max(a,b)
3. same for absolute value i.e. c=abs(a) so i have to constantly write c=a>0?a:-a
4. and so on....

Ideally, I could write these functions into an awk source file, and "include" it into all of my instances of awk, so I can call them at will.

I looked into the "@include" functionality of GNU's gawk , but it just executes whatever is in the included script - i.e. I cannot call functions.

I was hoping to write some functions in e.g. mylib.awk, and then "include" this whenever I call awk.

I tried the -f mylib.awk option to awk, but the script is executed - the functions therein are not callable.

Answer 1

With GNU awk:

$ ls lib
prims.awk

$ cat lib/prims.awk
function abs(num) { return (num > 0 ? num : -num) }
function max(a,b) { return (a > b ? a : b) }
function min(a,b) { return (a < b ? a : b) }

$ export AWKPATH="$PWD/lib"

$ awk -i prims.awk 'BEGIN{print min(4,7), abs(-3)}'
4 3

$ cat tst.awk
@include "prims.awk"
BEGIN { print min(4,7), abs(-3) }

$ awk -f tst.awk
4 3

Answer 2

You can have multiple -f program-file options, so one can be your common functions and the other can be a specific problem solving awk script, which will have access to those functions.

awk -f common-funcs.awk -f specific.awk file-to-process.txt

I don't know if this is what you were looking for, but it's the best I've come up with. Here's an example:

$ cat common_func.awk
# Remove spaces from front and back of string
function trim(s) {
  gsub(/^[ \t]+/, "", s);
  gsub(/[ \t]+$/, "", s);
  return s;
}

$ cat specific.awk
{ print $1, $2 }
{ print trim($1), trim($2) }

$ cat file-to-process.txt 
abc    |    def   |

2$ awk -F\| -f common_func.awk -f specific.awk file-to-process.txt 
abc         def   
abc def

With regular awk (non-gnu) you can't mix the -f program-file option with an inline program. That is, the following won't work:

awk -f common_func.awk '{ print trim($1) }' file-to-process.txt # WRONG 

As pointed out in the comments, however, with gawk you can use the -f option together with -e:

awk -f file.awk -e '{stuff}' file.txt