How to execute parallel commands

Question

Im working on large project and we have multiple npm packages.

I want to install all the packages in parallel which mean that i want all of to run on the same time (to save time) and once the last install has finished to continue with my script.

Example script:

#!/bin/zsh
#...

NPM_FOLDERS=(
    common.library/audit
    common.library/cipher
    common.library/logger
    ...
)

# Get the number of total folders to process
counter=${#NPM_FOLDERS[@]};

# counter for user feedback to the current install folder index
index=1;

# loop and install all the required packages
for folder in $NPM_FOLDERS;
do 
    #  Print the installation message with the folder & couters
    echo "\033[38;5;255m($index/$counter) Executing npm install in: \033[38;5;226m$folder";
    
    # change the folder to the required location    
    cd $ROOT_FOLDER/$folder;
    
    # Execute install on this folder
    npm install ;
   
    # increase current index
    let index++;

done

echo
echo "\033[38;5;11mInstallation completed."
echo

In not going to accept the fastest answer but the one who will do what i wish to do and do not have the right knowledge on how to do it, so you can tale the time and give a full answer.

Thank you very much in advance.

`npm install &`? Not sure how to explicitly wait for background processes, though. — Benjamin W., Dec 31 '15 at 23:32

Barmar · Accepted Answer · 2016-01-01T00:31:43.290

5

Execute npm install in the background with:

npm install &

Then after the done line you can wait for all the background processes to finish with:

wait

This command is explained in the bash manual:

Wait until the child process specified by each process ID pid or job specification jobspec exits and return the exit status of the last command waited for. If a job spec is given, all processes in the job are waited for. If no arguments are given, all currently active child processes are waited for, and the return status is zero.

edited Jan 01 '16 at 00:31

answered Dec 31 '15 at 23:51

Barmar

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But this will not wait until the last one will install. i need to install 20+ process and wait until the last one will finish. will it work? – CodeWizard Jan 01 '16 at 00:10
What will the wait do? will it wait for all the processes? – CodeWizard Jan 01 '16 at 00:11
If you run `wait` with no arguments, it waits for all background processes. – Barmar Jan 01 '16 at 00:14
Why would you assume I was wrong, instead of reading the documentation and confirming that what I wrote would work as you want? – Barmar Jan 01 '16 at 00:15
Not assuming you are wrong. just trying to understand what is it doing. I appropriate it. just trying to understand it – CodeWizard Jan 01 '16 at 00:18
It's working like a charm. Thank you very much, – CodeWizard Jan 01 '16 at 00:20
What does the wait do at the end? i understand its waiting for all the process, is there place where i can read about it to learn how it works? – CodeWizard Jan 01 '16 at 00:22
Appropriate your help, accepted and voted for your answer. Can you please explain what the wait does in few words? – CodeWizard Jan 01 '16 at 00:27
1

It waits for all background processes to finish, just like I said in the answer. – Barmar Jan 01 '16 at 00:29
Thank you, i learned something new thanks to you, – CodeWizard Jan 01 '16 at 00:30
1

I've added an excerpt from the documentation, because you don't know how to google. – Barmar Jan 01 '16 at 00:32
Thank you, Have a great new year. – CodeWizard Jan 01 '16 at 00:40

How to execute parallel commands

Example script:

1 Answers1