Using shell variable in awk

Question

I am new to awk and need some help

this works

awk '{
for(i =0;i<10;i++){
if ($27 == 'addr1') {
    print >"temp.csv"
     }
    }
}' /tmp/input.csv

i tried below and is not working, how to pass count value from outside to awk command

count=10
echo $count
awk '{
for(i =0;i<count;i++){
if ($27 == 'addr1') {
    print >"temp.csv"
     }
    }
}' /tmp/input.csv

possible duplicate of [Can we use shell variables in awk?](http://stackoverflow.com/questions/15786777/can-we-use-shell-variables-in-awk) — tripleee, Jan 02 '14 at 19:04
What are you trying to achieve? Do you want to print a line 10 times to a new file if field number 27 is equal to `"addr1"`? — Håkon Hægland, Jan 02 '14 at 19:13

score 5 · Accepted Answer · answered Jan 02 '14 at 19:02

5

Use the -v option to set a variable inside awk:

awk -v count="$count" '...'

"Filename" arguments of the form X=Y are also interpreted as variable assignments. The following should work:

awk '...' count="$count" /tmp/input.csv

answered Jan 02 '14 at 19:02

chepner

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Håkon Hægland · Answer 2 · 2014-01-02T19:24:18.937

If you want compare against a string inside awk, you need double quotes around the string. Like

awk -v count=$count '
$27=="addr1" {
  for(i=0;i<count;i++)
     print > "temp.csv" 
}' /tmp/input.csv

(Note that for instance 'if ($27 == 'addr1')' will expand to 'if ($27 == addr1)', that is: addr1 without double quotes)

If you instead want compare against the shell variable $addr1 inside awk, you can do

awk -v count=$count -vaddr1="$addr1" '
$27==addr1 {
  for(i=0;i<count;i++)
     print > "temp.csv" 
}' /tmp/input.csv

score 1 · Answer 3 · answered Jan 02 '14 at 19:02

1

You use the -v argument to awk to pass in values from the outside as awk variables.

count=2
echo $count
awk -vcount=$count '{
for(i =0;i<count;i++){
if ($27 == 'addr1') {
    print >"temp.csv"
     }
    }
}' /tmp/input.csv

answered Jan 02 '14 at 19:02

Etan Reisner

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Juan Diego Godoy Robles · Answer 4 · 2015-12-11T09:23:01.770

1

You can use a simply trick : break the awk code enclosure (single quotes) to put what you want inside, a piece of embedded code.

> a=10                                                                                                          
> awk 'BEGIN{for (i=0;i<='${a}';i++){printf("%d ", i)}}'
0 1 2 3 4 5 6 7 8 9 10

The good: Simple and handy.

The bad: It makes your program less readable .

edited Dec 11 '15 at 09:23

answered Jan 09 '14 at 06:54

Juan Diego Godoy Robles

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Using shell variable in awk

4 Answers4