Useful commands and scripts

Some here are scripts, those begin with a shebang

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#!

replace in place with sed

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sed -i -e 's/^/#/' filename

-u to turn off buffering for sed

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dmesg -T --follow | sed -u -e "s/^/$HOSTNAME/"

pz (pythonize shell)

operate on s (the line variable).

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echo -e "example\nwikipedia" | pz 's += ".com"'

mail

mailutils.txt

3.5.2.1 Syntax of mail internal commands

Open the default inbox (mbox) instead of the spool file.

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mail -f

With mail open, match string from the body.

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h :/\\[SPAM\\]

Match string from the header From.

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h From:/root

Header is Subject if omitted. Escaped to prevent an attempt to POSIX regex match.

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h /\\[SPAM\\]

Delete matching messages.

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d /\\[SPAM\\]

moreutils

chronic: runs a command quietly unless it fails combine: combine the lines in two files using boolean operations errno: look up errno names and descriptions ifdata: get network interface info without parsing ifconfig output isutf8: check if a file or standard input is utf-8 ifne: run a command if the standard input is not empty lckdo: execute a program with a lock held (deprecated) mispipe: pipe two commands, returning the exit status of the first parallel: run multiple jobs at once pee: tee standard input to pipes sponge: soak up standard input and write to a file ts: timestamp standard input vidir: edit a directory in your text editor vipe: insert a text editor into a pipe zrun: automatically uncompress arguments to command

ncdu equivalent

For when ncdu is not installed.

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du -d1 -h | sort -h

Faster alternatives written in Rust

fd - alternative to find. debian package name fd-find, executable name on debian is

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fdfind

ripgrep - alternative to grep. debian package name ripgrep.

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rg

pass

Unix style password management script, encrypts with gpg.

find and play videos flexibly

Using mpv, my preferred video player.

To use as is, create a shell script with below contents, arguments:

1st argument - how long ago was the video file last changed.

The rest of the arguments: path(s) to look for videos (glob, like

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/media/videos/201*

can be used as argument).

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#!/bin/sh
find -L "${@:2}" \( -iname '*.mp4' -o -iname '*.webm' -o -iname '*.avi' \) -a -ctime -"$1" -print0 | xargs -0 mpv

Rude wget robot to recursively download a site

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#!/bin/sh
# shows the correct script path even if called from another script
if [ -z "$1" -o -z "$2" ]; then
  echo "Usage: $(basename $(readlink -nf $0)) site_to_download_recursively destination_directory" 
  exit 1
else
  wget --continue --recursive --execute robots=off --wait 1 --directory-prefix="$2" "$1"
  # Below line for offline mirroring, test on each site.
  # wget  --mirror --convert-links --adjust-extension --page-requisites --no-parent --continue --recursive --execute robots=off --wait 1 --directory-prefix="$2" "$1"
  exit 0
fi

ImageMagick

Requires ImageMagick

Resize .jpg pictures in current directory level to roughly 1500x2000 pixels in size.

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mogrify -resize 1500x2000 *.{jpg,JPG}

Create a black background in required size (for example, to use in a video).

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convert -size 1920x1080 xc:black bg.png

FFMpeg

Dump audio using parallel. Parallel uses 1 thread for each core by default.

Make sure to change audio format according to source.

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parallel ffmpeg -i '{}' -map 0:1 -c:a copy '{.}.m4a' ::: /media/video/source_video_file.mkv