parallel call multiple bash functions

Question

I have read the example at http://www.gnu.org/software/parallel/man.html#example__calling_bash_functions however, is it possible to use gnu parallel to call 2 functions which do not have any variables you pass to them ?

example

a() {
  echo "download a"
  wget fileA
}

b() {
  echo "download b"
  wget fileB
}

and use parallel to call both functions a & b ?

I think that you have to make two different scripts and call them with parallel. — terence hill, Dec 21 '15 at 14:08
Instead of using GNU parallel, could you just call the functions in the background? Like `a &; b` to run `a` concurrently with `b`? — chrisaycock, Dec 21 '15 at 15:38

score 27 · Accepted Answer · answered Dec 21 '15 at 15:38

27

Run them in background. And then wait for them to complete.

a() {
  echo "download a"
  wget fileA
}

b() {
  echo "download b"
  wget fileB
}

a &
b &
wait # waits for all background processes to complete

answered Dec 21 '15 at 15:38

Ole Tange · Answer 2 · 2021-05-28T21:24:17.417

9

If you insist on using GNU Parallel:

a() {
  echo "download a"
  wget fileA
}

b() {
  echo "download b"
  wget fileB
}
export -f a
export -f b
parallel ::: a b

If you need read access to variables in the shell you can either export the variables or use env_parallel.

edited May 28 '21 at 21:24

answered Dec 21 '15 at 21:44

Ole Tange

1

This won't work if your function need to access some variables from the context. – agate May 28 '21 at 03:28

2 Answers2