Estou tentando aprender o GNU Parallel porque tenho um caso em que acho que poderia facilmente paralelizar uma função bash. Então, ao tentar aprender, fui aoManual do GNU Parallel onde háum exemplo... mas eu nem consigo fazê-lo funcionar! A saber:

(232) $ bash --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
(233) $ cat tpar.bash
#!/bin/bash

echo `which parallel`
doit() {
  echo Doing it for $1
  sleep 2
  echo Done with $1
}
export -f doit
parallel doit ::: 1 2 3
doubleit() {
  echo Doing it for $1 $2
  sleep 2
  echo Done with $1 $2
}
export -f doubleit
parallel doubleit ::: 1 2 3 ::: a b

(234) $ bash tpar.bash
/home/mathomp4/bin/parallel
doit: Command not found.
doit: Command not found.
doit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.

Como você pode ver, não consigo nem mesmo executar um exemplo simples. Assim, provavelmente estou fazendo algo incrivelmente estúpido e básico ... mas estou perdido.

ETA: Como sugerido pelos comentaristas (chmod + x, defina -vx):

(27) $ ./tpar.bash

echo `which parallel`
which parallel
++ which parallel
+ echo /home/mathomp4/bin/parallel
/home/mathomp4/bin/parallel

doit() {
  echo Doing it for $1
  sleep 2
  echo Done with $1
}
export -f doit
+ export -f doit
parallel doit ::: 1 2 3
+ parallel doit ::: 1 2 3
doit: Command not found.
doit: Command not found.
doit: Command not found.
doubleit() {
  echo Doing it for $1 $2
  sleep 2
  echo Done with $1 $2
}
export -f doubleit
+ export -f doubleit
parallel doubleit ::: 1 2 3 ::: a b
+ parallel doubleit ::: 1 2 3 ::: a b
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.
doubleit: Command not found.

ETA2: Note, eu posso, no script, simplesmente chamar 'doit 1', digamos, e ele fará isso. Portanto, a função é válida, simplesmente não é ... exportada?