Bash variable in AWK

Question

I'm trying to pass variable in loop with awk command to find values. I have a file:

input.txt

1234|something|ohmygod
2345|urabura|kangura
9999|1234|xxxsecrets

shell command

cat input.txt | awk -F'|' '$1 ~ /1234/'

or

awk -F'|' '$1 ~ /1234/' input.txt

get first line from file as desired. Problem occurs when I try to print this via bash. When I simply test echo like:

echo `cat input.txt | awk -F'|' '$1 ~ /1234/'`

or

echo `awk -F'|' '$1 ~ /1234/' input`

I got desired output, but unfortunately when I try to pass variable inside it

variable1="1234"
echo `awk -F'|' '$1 ~ /"$variable1"/' input`

or

variable1="1234"
echo `awk -v var="$variable1" -F'|' '$1 ~ /var/' input`

it gives one empty line. Please suggest how to pass variable inside regex awk filter.

PS It is not duplicate question to: How do I use shell variables in an awk script? due to fact that I have knowledge how to use variable in AWK as I posted up here (-v parameter) but the question is how to PASS variable in REGEX in AWK (place between two slashes - echo awk -F'|' '$1 ~ /"$variable"/' input)

As an aside, `echo $(cmd)` is a [useless use of `echo`](http://www.iki.fi/era/unix/award.html#echo) unless you specifically require the shell to perform whitespace tokenization and variable substitution on the output from `cmd`. (The older syntax with backticks ` \`cmd\` ` is obsolescent and should be avoided. — tripleee, Feb 26 '18 at 12:39
It doesn't do that, it introduces new hard-to-debug corner cases. — tripleee, Feb 26 '18 at 14:13
@tripleee but shell does not have any variable "watcher" so how to debug my changes? — Wont Provide, Feb 26 '18 at 16:28

score 0 · Answer 1 · answered Feb 26 '18 at 12:40

0

What you asked for:

awk -v var="$variable1" -F'|' '$1 ~ var' input

What you actually need:

awk -v var="$variable1" -F'|' '$1 == var' input

See http://cfajohnson.com/shell/cus-faq-2.html#Q24

answered Feb 26 '18 at 12:40

Ed Morton

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Unfortunately changing ~ to "" does not help. – Wont Provide Feb 26 '18 at 14:06
1

That's not what Ed is suggesting. – tripleee Feb 26 '18 at 14:14
@WontProvide where do you see `~` being changed to `""`? – Ed Morton Feb 26 '18 at 16:08
@EdMorton my typo, I mean == – Wont Provide Feb 26 '18 at 16:28
Changing `~` to `==` wasn't intended to answer the question you asked, that's what changing `/var/` to `var` does. Changing `~` to `==` makes it a full string comparison instead of a partial regexp comparison and so avoids false matches. – Ed Morton Feb 26 '18 at 16:32
@EdMorton Oh, thank you. Unfortunately I'm still looking for an answer how to pass variable to regexp comparison. – Wont Provide Feb 26 '18 at 22:17
@WontProvide did you try what I showed you? That first script **IS** how to pass a variable for a regexp comparison. `~` is the regexp comparison operator and `var` is the variable. – Ed Morton Feb 26 '18 at 22:36

Bash variable in AWK

1 Answers1