awk - send variable to .awk script and use as conditional

Question

I want to send a variable to my external .awk script to use as a conditional. The following script is however not working.

Here first is the command:

awk -v myVar="optA" -f /users/test/fixit.awk /users/test/input.txt > /users/test/output.txt

The sample fixit.awk script is:

BEGIN { printf "TITLE:\nDocuments \n", myVar, FS=" "; }

if (myVar="optA")
      printf myVar
else 
      printf "OptB"

Can someone please help diagnose the problem?

You probably don't mean to have a comma before FS=" ". Also, you probably don't even need that FS assignment at all, because the default input field separator is white space. — e0k
– e0k, Commented Feb 2, 2016 at 0:29
See Assigning Variables on the Command Line from GNU awk documentation. Also, reading a nice tutorial might help too. — e0k
– e0k, Commented Feb 2, 2016 at 0:37

Benjamin W. · Accepted Answer · 2016-02-02 01:13:28Z

2

An awk assignment is also an expression with the return value of what was assigned. If you write

if (myVar = "optA")

you actually check the return value of the assignment, optA, which awlays evaluates to "true". You want

if (myVar == "optA")

for comparison instead of assignment.

Also, you can't have "naked" statements like this. Your if/else clause either has to be part of the BEGIN block:

BEGIN {
    printf "TITLE:\nDocuments \n", myVar, FS=" "

    if (myVar=="optA")
          printf myVar
    else 
          printf "OptB"
}

to execute once, or in a separate block if it should be executed for every single line (less likely, though):

BEGIN { printf "TITLE:\nDocuments \n", myVar, FS=" " }

{
    if (myVar=="optA")
        printf myVar
    else 
        printf "OptB"
}

As an aside, the way you use printf doesn't make much sense: you could either do

print "TITLE:\nDocuments\n" myVar

or

printf "TITLE:\nDocuments\n%s\n", myVar

And for printf myVar or printf "OptB", unless you explicitly don't want that newline, you can as well use print myVar and print "OptB".

And finally, that FS= assignment looks a bit out of place and is probably not needed as " " is the default value of FS.

answered Feb 2, 2016 at 0:23

Benjamin W.

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1 Comment

Thank you, I needed the execution blocks.