Multithreading in Bash [duplicate]

This question already has answers here: How do you run multiple programs in parallel from a bash script? (19 answers) Closed 5 years ago. 开发者_如何学运维

I would like to introduce multithreading feature in my shell script.

I have a script which calls the function read_cfg() with different arguments. Each of these function calls are independent.

Would it be possible to instantiate these function calls (not scripts) parallelly. Please let me how can we achieve that.. ?

---

Sure, just add & after the command:

read_cfg cfgA &
read_cfg cfgB &
read_cfg cfgC &
wait

all those jobs will then run in the background simultaneously. The optional wait command will then wait for all the jobs to finish.

Each command will run in a separate process, so it's technically not "multithreading", but I believe it solves your problem.

---

You can run several copies of your script in parallel, each copy for different input data, e.g. to process all *.cfg files on 4 cores:

    ls *.cfg | xargs -P 4 -n 1 read_cfg.sh

The read_cfg.sh script takes just one parameters (as enforced by -n)

---

Bash job control involves multiple processes, not multiple threads.

You can execute a command in background with the & suffix.

You can wait for completion of a background command with the wait command.

You can execute multiple commands in parallel by separating them with |. This provides also a synchronization mechanism, since stdout of a command at left of | is connected to stdin of command at right.