Calling multiple bash scripts and running them in parallel, not in sequence

Question

Suppose that I have three (or more) bash scripts: script1.sh, script2.sh, and script3.sh. I would like to call all three of these scripts and run them in parallel. One way to do this is to just execute the following commands:

nohup bash script1.sh &
nohup bash script2.sh &
nohup bash script3.sh &

(In general, the scripts may take several hours or days to finish, so I would like to use nohup so that they continue running even if my console closes.)

But, is there any way to execute those three commands in parallel with a single call?

I was thinking something like

nohup bash script{1..3}.sh &

but this appears to execute script1.sh, script2.sh, and script3.sh in sequence, not in parallel.

Answer 1

for((i=1;i<100;i++)); do nohup bash script${i}.sh & done

Answer 2

A better way would be to use GNU Parallel. GNU parallel is simple and with it we can control the number of jobs to run in parallel with more control over the jobs.

In the below command, script{1..3}.sh gets expanded and are sent as arguments to bash in parallel. Here -j0 indicates that as many jobs should be run as possible. By default parallel runs one job for one cpu core.

$ parallel -j0 bash :::: <(ls script{1..3}.sh)

And you can also try using

$ parallel -j0 bash ::: script{1..3}.sh

While executing the second method if you get any error message then it means that --tollef option is set in /etc/parallel/config and that needs to be deleted and every thing will work fine.

You can read GNU Parallels man page here for more richer options.

And in case if your are running the jobs from a remote machine, better use screen so that the session does not gets closed due to network problems. nohup is not necessary, as recent versions of bash as coming with huponexit as off and this will prevent parent shell from sending HUP signal to its children during its exit. In case if its not unset do it with

$ shopt -u huponexit  

Answer 3

We can also use xargs to run multiple script in parallel.

$ ls script{1..5}.sh|xargs -n 1 -P 0 bash

here each script is passed to bash as argument separately. -P 0 indicates that the number of parallel process can be as much as possible. It is also safer that using bash default job control feature (&).

Answer 4

A single line solution:

$ nohup bash script1.sh & nohup bash script2.sh & nohup bash script3.sh &

Less facetiously, just use a wrapper script:

$ cat script.sh
#!/usr/bin/env bash
script1.sh &
script2.sh &
script3.sh &
$ nohup script.sh &

Or loop over them:

for script in dir/*.sh
do
    nohup bash "$script" &
done

Answer 5

If you're looking to save yourself some typing effort

eval "nohup bash "script{1..3}.sh" &"

Or on second thoughts, maybe not

Answer 6

I am suggesting a much simpler utility I just wrote. It's currently called par, but will be renamed soon to either parl or pll, haven't decided yet.

https://github.com/k-bx/par

API is as simple as:

par "script1.sh" "script2.sh" "script3.sh"

Answer 7

Use parallelshell

parallelshell "echo 1" "echo 2" "echo 3"

https://github.com/keithamus/parallelshell

Answer 8

Checkout this tool: https://github.com/wagoodman/bashful

Say you have mytasks.yaml with

tasks:
    - name: A title for some tasks
      parallel-tasks:
        - cmd: ./script1.sh
        - cmd: ./script2.sh -x an-arg
        - cmd: ./script3.sh -y some-other-arg

And you run it like so:

nohup bashful run mytasks.yaml

Your scripts would be run in parallel with a vertical progress bar (+eta if you've run it before and the time is deterministic). You can tweak how many tasks you want to run in parallel if you start running more than just the given 3 here:

config:
    max-parallel-commands: 6
tasks:
    ...

Disclaimer: I'm the author.

Answer 9

Write all your commands to a parent script (parent_script.sh) which looks like the following:

bash script1.sh &
bash script2.sh &
bash script3.sh &
wait

Adding "wait" at the end of the your script will run it in parallel. Then submit the parent script with nohup.

nohup bash parent_script.sh