My personal doodle pad about everything that has anything to do with technology...
Let’s assume that an MP4 video file has two audio streams, but you only want to keep one.
The following line will create a new mp4 video file that only has the first audio stream:
ffmpeg -i input.mp4 -map 0:v:0 -map 0:a:0 -c copy output.mp4The following line will create a new mp4 video file that only has the second audio stream:
ffmpeg -i input.mp4 -map 0:v:0 -map 0:a:1 -c copy output.mp4Sometimes, one wants to check if Apache2 is running. This is one way how to do it in BASH:
if [ "$(systemctl is-active apache2)" = "active" ]; then
echo "Apache2 is active"
ApacheIsRunning=1
else
echo "Apache2 is not active"
ApacheIsRunning=0
fiOnce in a while, a Bash script needs to query its own name and directory. Here is an example on how to do that:
#!/usr/bin/bash
ThisScriptsName="$(basename -- "${BASH_SOURCE[0]}")"
ThisScriptsDirectoryAndName="$(readlink -f -- "${BASH_SOURCE[0]}")"
ThisScriptsDirectory="$(dirname -- "$ThisScriptsDirectoryAndName")"
TheCurrentDirectory="$(pwd)"
printf 'ThisScriptsName: %s\n' "$ThisScriptsName"
printf 'ThisScriptsDirectoryAndName: %s\n' "$ThisScriptsDirectoryAndName"
printf 'ThisScriptsDirectory: %s\n' "$ThisScriptsDirectory"
printf 'TheCurrentDirectory: %s\n' "$TheCurrentDirectory"
#EOFLet’s assume the name of the file is WhatsMyNameAndLocation, and it is located in /usr/scripts and executed from / with /usr/WhatsMyNameAndLocation:
ThisScriptsName: WhatsMyNameAndLocation
ThisScriptsDirectoryAndName: /usr/scripts/WhatsMyNameAndLocation
ThisScriptsDirectory: /usr/scripts
TheCurrentDirectory: /timedatectl list-timezones to find a zone, then timedatectl set-timezone [timezone]