awk: setting environment variables directly from within an awk script

Question

first post here, but been a lurker for ages. i have googled for ages, but cant find what i want (many abigious topic subjects which dont request what the topic suggests it does ...). not new to awk or scripting, just a little rusty :)

i'm trying to write an awk script which will set shell env values as it runs - for another bash script to pick up and use later on. i cannot simply use stdout from awk to report this value i want setting (i.e. "export whatever=awk cmd here"), as thats already directed to a 'results file' which the awkscript is creating (plus i have more than one variable to export in the final code anyway).

As an example test script, to demo my issue:

echo $MYSCRIPT_RESULT          # returns nothing, not currently set
echo | awk -f scriptfile.awk   # do whatever, setting MYSCRIPT_RESULT as we go
echo $MYSCRIPT_RESULT          # desired: returns the env value set in scriptfile.awk 

within scriptfile.awk, i have tried (without sucess)

1/) building and executing an adhoc string directly:

{
  cmdline="export MYSCRIPT_RESULT=1"
  cmdline
}

2/) using the system function:

{
  cmdline="export MYSCRIPT_RESULT=1"
  system(cmdline)
}

... but these do not work. I suspect that these 2 commands are creating a subshell within the shell awk is executing from, and doing what i ask (proven by touching files as a test), but once the "cmd"/system calls have completed, the subshell dies, unfortunatley taking whatever i have set with it - so my env setting changes dont stick from "the caller of awk"'s perspective.

so my question is, how do you actually set env variables within awk directly, so that a calling process can access these env values after awk execution has completed? is it actually possible?

other than the adhoc/system ways above, which i have proven fail for me, i cannot see how this could be done (other than writing these values to a 'random' file somewhere to be picked up and read by the calling script, which imo is a little dirty anyway), hence, help!

all ideas/suggestions/comments welcomed!

Answer 1

You cannot change the environment of your parent process. If

MYSCRIPT_RESULT=$(awk stuff)

is unacceptable, what you are asking cannot be done.

Answer 2

You can do this, but it's a bit of a kludge. Since awk does not allow redirection to a file descriptor, you can use a fifo or a regular file:

$ mkfifo fifo
$ echo MYSCRIPT_RESULT=1 | awk '{ print > "fifo" }' &
$ IFS== read var value < fifo
$ eval export $var=$value

It's not really necessary to split the var and value; you could just as easily have awk print the "export" and just eval the output directly.