byte-cook / bash-alias-and-function

Use these shortcuts to make bash even simpler

Bash Alias and Function

This project contains useful bash aliases and functions. Bash aliases are essentially shortcuts that save you from having to remember long commands and save you a lot of typing when working on the command line.

To make the alias or function persistent you need to declare it in the ~/.bashrc file. If you want to make your ~/.bashrc more modular, you can store your aliases in a separate file. Some distributions, such as Ubuntu and Debian, include a ~/.bash_aliases file that is referenced in ~/.bashrc.

Pick the shortcuts you are interested in and copy the code into one of the files mentioned above.

Run alias commands as root

Alias definition:

sudo='sudo '

Usage:

sudo <youralias>

How it works: If the last character of the alias value is a blank, then the next command word following the alias is also checked for alias expansion. See https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html?ref=linuxhandbook.com#Aliases.

Mount iso file

Alias definition:

function mount.iso() {
    # $1: the iso file
    if [ $# -eq 1 ]; then
        sudo mkdir -p /media/iso 
        sudo mount -o loop -t iso9660 "$1" /media/iso
    else
        echo Usage: mount.iso \<iso-file\>
    fi
}
function umount.iso() {
    sudo umount /media/iso
    sudo rmdir /media/iso
}

Convert video files

Convert MP4 files to MP3 files:

alias convert.mp42mp3='for f in *.mp4; do ffmpeg -i "$f" "${f%.mp4}.mp3"; done'

Convert MOV files to MP4 files

alias convert.mov2mp4='for i in *.mov; do ffmpeg -i "$i" -vcodec h264 -crf 30 -acodec aac "${i%.mov}_new.mp4"; done'

Convert high quality MP4 files to MP4 files with lower quality:

alias convert.mp42mp4='for i in *.mp4; do ffmpeg -i "$i" -vcodec h264 -crf 30 -acodec aac "${i%.mp4}_new.mp4"; done'

Or if the conversion is to be done for individual files:

function convert.mp42mp4.file() {
    # $1: input file name
    if [ "$#" == 0 ]; then
        echo Usage: convert.mp42mp4.file \<file\> [\<file\> ...]
        return 1
    else
        for n in "$@"
        do
            if [ "${n##*.}" == "mp4" ]; then
                outputFile="${n%.*}"_new.mp4
                ffmpeg -i "$n" -vcodec h264 -crf 30 -acodec aac "$outputFile"
            fi
        done
    fi
}

Download m3u8 file

function download.m3u8 {
    # $1: m3u8 url
    # $2: output filename
    if [ $# -eq 2 ]; then
        cd ~/Downloads
        ffmpeg -protocol_whitelist file,http,https,tcp,tls,crypto -i "$1" -c copy "$2"
    else
        echo Usage: download.m3u8 \<m3u8-url\> \<output-file\>
    fi
}

Create folders for MP3 CD

function mkdir.mp3() {
    # $1: start index
    if [ "$#" != 1 ]; then
        echo Usage: mkdir.mp3 \<start-index\>
        return 1
    else
        # check input
        if [ $(($1 % 6)) != 1 ]; then
            echo Error: Input is not a valid start index
            return 1
        fi
        
        lastIndex=$(($1+5))
        folder=MP3_$1-$lastIndex
        for i in $(seq $1 $lastIndex);
        do
            mkdir -p $folder/MP3_$i
        done
    fi
}

Encrypt/decrypt tar archives

function tar.encrypt() {
    # $1...: files or folders to encrypt
    if [ "$#" == 0 ]; then
        echo Usage: tar.encrypt \<file\> [\<file\> ...]
        return 1
    else
        tar czvpf - "$@" | gpg --symmetric --cipher-algo aes256 -o archive.tar.gz.gpg
    fi
}

function tar.decrypt() {
    # $1: archive to decrypt
    if [ "$#" != 1 ]; then
        echo Usage: tar.decrypt \<archive\>
        return 1
    else
        gpg -d $1 | tar xzvf -
    fi
}

Find files containing search text

function grep.findfiles() {
    # $1: search text
    # $2: directory
    if [ "$#" != 2 ]; then
        echo Usage: grep.findfiles \<search-text\> \<directory\>
        return 1
    else
        # -R: recursive
        # -i: ignore case
        # -l: print the name of the files
        grep -Ril "$1" "$2"
    fi
}

Appendix: Bash programming reference

https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

${param#pattern} : pattern must match the beginning of param, the rest is returned
${param%pattern} : pattern must match the ending of param, the rest is returned