how to check if awk array is empty

Question

I am brand new to AWK and trying to determine if my array is empty or not so i can print a message if so. Typically i am use to length functions and can check like that, but it does not seem AWK has those. Here is my working code, i just want to print out a different message if there is nothing in the array after parsing all my data.

#add to array if condition is met
if ($2 == "SOURCE" && $4 == "RESTRICTED"){
    sourceAndRestricted[$3]++;
}
#print out array
for (var in sourceAndRestricted){
    printf "\t\t"var"\n" 
}

ive tried something like this and its not working. Suggestions?

for (var in sourceAndRestricted){
    if (var > 1){
        printf "\t\t"var"\n" 
    }
    else {
        print "NONE"
    }
}

Keep a counter in the for loop and check it after?

Etan Reisner
– Etan Reisner

2013-11-19 15:48:57 +00:00
Commented Nov 19, 2013 at 15:48 — Etan Reisner
– Etan Reisner, Commented Nov 19, 2013 at 15:48

Birei · Accepted Answer · 2013-11-19 15:46:51Z

11

Check it with length() function:

if ( length(sourceAndRestricted) > 0 ) {
    printf "\t\t"var"\n"
}
else
    print "NONE"
}

answered Nov 19, 2013 at 15:46

Birei

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6 Comments

Etan Reisner Over a year ago

gawk 3.1.5 and newer only. I don't know about other awk:s.

Birei Over a year ago

@EtanReisner: It works for me with --traditional switch too, that teorically make it works without GNU extensions.

Vinnie Biros Over a year ago

did not know there was a length function! Thank you very much, this worked!

Ed Morton Over a year ago

length(array) is considered an extension in gawk and I hear it works in OSX awk too but it's definitely not portable.

James Brown Over a year ago

There is a downside to this: gawk 'BEGIN{if(length(arr)==0) arr[1]=1}' produces an error: gawk: cmd. line:1: fatal: attempt to use scalar 'arr' as an array.

|

Ed Morton · Accepted Answer · 2013-11-19 17:26:37Z

11

$ cat tst.awk
function isEmpty(arr, idx) {for (idx in arr) return 0; return 1}

BEGIN {
   map[3] = 27

   print isEmpty(map)

   delete map[3]

   print isEmpty(map)
}
$ awk -f tst.awk
0
1

answered Nov 19, 2013 at 17:26

Ed Morton

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