export function from zsh to bash for use in gnu parallel

Question

How do I export a function from zsh, so that I can use it in gnu parallel?

example:

function my_func(){ echo $1;}
export -f my_func
parallel "my_func {}" :::  1 2

in bash will output

1
2

whereas in zsh it will output error messages

/bin/bash: my_func: command not found
/bin/bash: my_func: command not found

Why do your error messages begin with `/bin/bash`? Does that mean that GNU `parallel` is running `/bin/bash` despite the fact that you have `SHELL=/bin/zsh` set in the environment? Or do you have `SHELL=/bin/bash` set? — Jonathan Leffler, Mar 29 '14 at 23:57
@JonathanLeffler I think `parallel`, being another GNU program, tries to interpret a missing command as a function, in which case it spawns a `bash` shell to attempt to call it. — chepner, Mar 30 '14 at 00:42

score 9 · Answer 1 · answered Mar 29 '14 at 23:58

9

zsh does not have a concept of exporting functions. export -f somefunc will print the function definition, it will not export a function.

Instead, you can rely on the fact that bash functions are exported as regular variables starting with ():

export my_func='() { echo "$1"; }'
parallel --gnu "my_func {}" ::: 1 2

answered Mar 29 '14 at 23:58

that other guy

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1

That is true but can you *rely* on it? It's certainly not documented. – rici Mar 30 '14 at 01:22
4

As the author of GNU Parallel I can say that GNU Parallel relies on that when transferring functions to remote machines. I was quite baffled, when I found out that you cannot have a normal variable that starts with '() {' This had quite unexpected results: i='() {' bash -c 'echo $i' – Ole Tange Mar 30 '14 at 02:01
This even works with mutiline functions! `function my_func(){ echo $1;}` `export my_func="`whence -f my_func | sed -e 's/my_func //' `"` `parallel "my_func {}" ::: 1 2` – Bilal Syed Hussain Mar 30 '14 at 02:19
1

@OleTange The zsh workaround specified in the [man page](http://www.gnu.org/software/parallel/man.html) doesn't seem to work. I'm running zsh 5.0.5. Any ideas? – nachocab Nov 02 '14 at 20:36
2

@nachocab Yeah: It seems the workaround was killed by the Shellshock fix in Bash. Currently I have no solution to that. If you find one, please let me know. – Ole Tange Nov 02 '14 at 20:43
@WaelJ If you upgrade Bash to post-shellshock, you will also need to upgrade GNU Parallel to version Shellshock or later. – Ole Tange Nov 02 '14 at 20:44
@OleTange is this solution still valid? – shadowtalker Jun 28 '16 at 17:55
2

@ssdecontrol No. Use env_parallel to import zsh functions, variables, and arrays. – Ole Tange Jun 28 '16 at 17:59

score 6 · Answer 2 · answered Mar 30 '14 at 02:39

6

Based on that other guy's answer. You can write a function that export a zsh function that already defined to bash

function exportf (){
    export $(echo $1)="`whence -f $1 | sed -e "s/$1 //" `"
}

Usage

function my_func(){
    echo $1;
    echo "hello";
}

exportf my_func
parallel "my_func {}" :::  1 2

answered Mar 30 '14 at 02:39

Bilal Syed Hussain

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Wonderful function. With your permission it will go into the man-page of GNU Parallel. There is one minor snag: It does not work if $SHELL=zsh. So you need to overwrite SHELL=/bin/bash – Ole Tange Mar 30 '14 at 08:45
Sure add it man-page of GNU Parallel, adding it to the tutorial as well, would be probably be useful – Bilal Syed Hussain Mar 30 '14 at 14:55
Can the function be updated to work when in the case that Ole Tange mentioned? If so could you edit the answer to fix that case? (or have you already?) – dshepherd Jul 29 '14 at 09:16
If you find a way to fix it for the post-shellshock world, please update your answer. – Ole Tange Nov 02 '14 at 20:47
I have not been able to make it a function but this works, on my OS X 10.10 bash 3.2.53 . env '__BASH_FUNC()'="() { echo \$1;}" bash -c 'export -f a; SHELL=/bin/bash parallel a {} ::: 1 2 3' – Bilal Syed Hussain Nov 03 '14 at 05:56

score 5 · Accepted Answer · answered May 23 '18 at 21:50

5

A lot has changed since 2014.

Today you simply do:

# Activate env_parallel function (can be done in .zshenv)
. `which env_parallel.zsh`

function my_func(){ echo $1;}
env_parallel "my_func {}" :::  1 2

If your environment is big:

# Activate env_parallel function (can be done in .zshenv)
. `which env_parallel.zsh`

# Record which environment to ignore
env_parallel --session

function my_func(){ echo $1;}
env_parallel "my_func {}" :::  1 2

answered May 23 '18 at 21:50

Ole Tange

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I got `_bodies_of_ALIASES:alias:3: bad option: -o` when executing the 3rd command 1st code block. zsh: 5.8, parallel: 20210822. – Teddy C Sep 11 '21 at 14:22
@TeddyC File a bug report. I cannot reproduce it, so it depends on your environment. https://www.gnu.org/software/parallel/man.html#bug-dependent-on-environment – Ole Tange Sep 11 '21 at 18:34
Thanks for the reply! Tried it again in a clean zsh environment on my machine and it works. :) Perhaps the `env_parallel.zsh` script has conflict with some of my defined aliases / functions, but I'm not sure which ones. – Teddy C Sep 12 '21 at 04:29

score 3 · Answer 4 · answered Apr 09 '20 at 19:38

This approach allows you to define a function in zsh (without worrying about adding a quote level). Also it does not require adding additional software.

Make a function. Here's one:

function bar {
    echo bar
    echo $1
}

And spin it up:

seq 10 | xargs -I{} -n1 -P1 zsh -c "$(whence -f bar); bar {}"

I'm using xargs at the minute but of course the same approach works for GNU Parallel, so thought I'd share it here.

export function from zsh to bash for use in gnu parallel

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