Useful scripts

All Shell scripts are tested on GNU bash, version 4.4.20(1)-release.

Dependencies

• webp to convert image to webp format.

Parallel

Parallel helpers limit the number of background jobs by the processor logic number.

How to use it ?

# At the beggining of your script
# Import helpers/parallel file
. "<path to helpers/parallel>"

# Then init required variable
parallel::init

# Run command(s)
declare -a cmd=(sleep 5)
parallel::run cmd

# Wait for all jobs
parallel::wait

Benchmark

Code used to benchmark scripts based on UNIX timestamp in second with the command date "+%s".

declare -r -i start_time="$(date "+%s")"
parallel::init [max number of background jobs]
# Run some jobs with the command below
# Where cmd is an array describe a command like: (sleep 5)
parallel::run cmd
declare -r -i end_time="$(date "+%s")"
echo "$((end_time - start_time)) seconds"

All result are tested on my machine with 8 logic processors _NPROCESSORS_ONLN.

Compress img

Command line:

$ ./multimedia/compress-img.sh --webp --force <directory with 10 png picture>

Max number of background jobs	Total time (in second)
8	4, 3
6	4
4	4
2	5, 6
1	11, 12

N.B: Result with 4, 6 and 8 background jobs are the similar because jobs have the time to finish. So algorithm wait jobs only in script end.