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Multi threading in UNIX


 
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# 1  
Old 09-07-2019
Multi threading in UNIX

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



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

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


Last edited by RavinderSingh13; 09-08-2019 at 06:02 AM..
# 2  
Old 09-08-2019
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.

Quote:
Multithreading is mainly found in multitasking operating systems. Multithreading is a widespread programming and execution model that allows multiple threads to exist within the context of one process. These threads share the process's resources, but are able to execute independently. The threaded programming model provides developers with a useful abstraction of concurrent execution. Multithreading can also be applied to one process to enable parallel execution on a multiprocessing system.
See, for example:

Thread (computing)
# 3  
Old 09-09-2019
The ls in your script omits the full path.
The following does not:
Code:
for file in $FILE_PATH/* 
do
  $OPT_PATH/load_script "$file" &
done

# 4  
Old 09-09-2019
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
- GNU Project - Free Software Foundation
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