How to coerce AWK to evaluate string as math expression?

Question

Is there a way to evaluate a string as a math expression in awk?

balter@spectre3:~$ echo \"sin(0.3) 0.3\" | awk \'{print $1,sin($2)}\'
sin(0.3) 0.29552
         


        

Answer 1

You can just create your own eval function which calls awk again to execute whatever command you want it to:

$ cat tst.awk
{ print eval($1), sin($2) }

function eval(str,      cmd,line,ret) {
    cmd = "awk \047BEGIN{print " str "; exit}\047"
    if ( (cmd | getline line) > 0 ) {
        ret = line
    }
    close(cmd)
    return ret
}

$ echo 'sin(0.3) 0.3' | awk -f tst.awk
0.29552 0.29552

$ echo '4*7 0.3' | awk -f tst.awk
28 0.29552

$ echo 'tolower("FOO") 0.3' | awk -f tst.awk
foo 0.29552