Multi threading in UNIX

UNIX for Beginners Q & A
1

Hi,

Can we apply multi threading in Unix. I am using bash shell.
We have a generic script to load the data to table based on file input. For each file there is an individual table to load.

For each file found in directory I want to load the data in parallel to target table using

for file in `ls $FILE_PATH` 
do
$OPT_PATH/load_script $file &
done;

$ for i in {2..5}; do
>     sleep $i &
> done
[1] 50350
[2] 50351
[3] 50352
[4] 50353
2

Multi threading in the UNIX environment is generally a kernel level process and there is no "multi threading" for commands in a script like you provide as an example.

However, you can "multi-processing" by running tasks in the background which you are already doing with the & appended after the command and you can wait for completion of a background command with the wait command.

See, for example:

Thread (computing)

3

The ls in your script omits the full path.
The following does not:

for file in $FILE_PATH/* 
do
  $OPT_PATH/load_script "$file" &
done
4

Suggestions: next time, be sure to tell us your OS and your shell, you will get better answers.
There is a command available from GNU called parallel which does exactly what you want. Also xargs and the & command

IF you have Linux this discusses and gives examples of each way to do what you want:

How to run command or code in parallel in bash shell under Linux or Unix - nixCraft
and
[GNU Parallel