awk How pass parameters to the function, called from inside awk

Question

Sample function:

$ testfn() { echo "${1} world"; }
$ testfn hello
hello world

awk example:

$ echo "something bla bla2"|awk '$1 ~/something/ { print $0; }'
something bla bla2

Now I want to change "something" to "something world" using created above function, when printing it as a whole line, by passing first awk " column element" as a parameter:

$ echo "something bla bla2"|awk '$1 ~/something/ { $1="'"$(testfn) $1"'" ; print $0 }'
 world  bla bla2

^^ Above doesn't work

Is there any way to pass parameters from awk to the function inside awk ?

The awk example in the 2nd block only prints "something bla bla2", it doesn't print the first line of "something". Is that a typo or is it something else? What OS is this and what version of awk/gawk are you using? — slm
– slm, Commented Feb 10, 2013 at 6:45

Ed Morton · Accepted Answer · 2013-02-10 14:06:08Z

2

Highly unrecommended but:

$ cat .env
testfn() { echo "${1} world"; }
$ echo $BASH_ENV
.env
$ echo "something bla bla2" | awk '$1 ~/something/{"bash -c \"testfn " $1 "\"" | getline $1; print $0}'
something world bla bla2

Now, tell us what you're really trying to do and we can help you write a sane script to do that.

answered Feb 10, 2013 at 14:06

Ed Morton

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2 Comments

hellish Over a year ago

Did everything as you've described. But getting errors: BASH_ENV=.env $ echo "something bla bla2" | awk '$1 ~/something/{"bash -c \"testfn " $1 "\"" | getline $1; print $0}' sh: -c: line 0: unexpected EOF while looking for matching `"' sh: -c: line 1: syntax error: unexpected end of file something bla bla2 I'm sending a table of values to awk. What I want is to replace one field in a 5th column, based on element in 1st column, and this element should be processed via complex function (based on SQL query result from database).

Ed Morton Over a year ago

Maybe your shell isn't bash and/or bash isn't available on your box? Just use whatever shell you normally use and save your function in whatever file your shell executes when a new non-login shell is started. You shouldn't do this anyway though. Unfortunately your explanation doesn't contain nearly enough information to help you write a script. If you'd like help, edit your question with sample input/output and a description of what your function should do.

Steve · Accepted Answer · 2013-02-10 23:52:08Z

1

No - you can't call shell functions from inside of awk. It's not a shell. However, a common workaround involves adding your function to a file and calling it using awk's system() function. Here's a simple example:

Contents of yourfunction.sh:

{
    echo "$1 world"
}

Then run:

echo "what the ..." | awk '{ system("./yourfunction.sh" FS $1) }'

Results:

what world

Note that if you find yourself having to do this, there's almost certainly a better approach. What are you actually trying to do here?

EDIT:

In response to the comments below, use the getline() function:

echo "what the ..." | awk '{ "./yourfunction.sh" FS $1 | getline $1 }1'

Results:

what world the ...

Here's some info re the getline() function:

http://www.gnu.org/software/gawk/manual/html_node/Getline.html

edited Feb 10, 2013 at 23:52

answered Feb 10, 2013 at 8:16

Steve

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3 Comments

hellish Over a year ago

Thank you! If I will not find another ways to achieve what I want, I'll have to try this workaround.

hellish Over a year ago

Hey, but this executes the function and displaying the output, what I'm trying to achieve is to replace fist element and then print the whole modified line. $ echo "what the ..." | awk '{ $1=system("./yourfunction.sh" FS $1); print; }' what world 0 the ...; I'm expecting result here as one line: "what world the ..."

Ed Morton Over a year ago

If you're considering using getline, make sure you read awk.info/?tip/getline and fully understand what you're getting yourself into.

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