Bash/Functions

To set trap to intercept a non-zero return code of the last program run:

EC() {
	echo -e '\e[1;33m'code $?'\e[m\n'
}
trap EC ERR

The following function will compile (within the /tmp/ directory) and execute the C source argument on the fly (and the execution will be without arguments). And finally, after program terminates, will remove the compiled file.

# Compile and execute a C source on the fly
csource() {
	[[ $1 ]]    || { echo "Missing operand" >&2; return 1; }
	[[ -r $1 ]] || { printf "File %s does not exist or is not readable\n" "$1" >&2; return 1; }
	local output_path=${TMPDIR:-/tmp}/${1##*/};
	gcc "$1" -o "$output_path" && "$output_path";
	rm "$output_path";
	return 0;
}

The following function will extract a wide range of compressed file types. Use it with the syntax extract <file1> <file2> ...

extract() {
    local c e i

    (($#)) || return

    for i; do
        c=''
        e=1

        if [[ ! -r $i ]]; then
            echo "$0: file is unreadable: \`$i'" >&2
            continue
        fi

        case $i in
            *.t@(gz|lz|xz|b@(2|z?(2))|a@(z|r?(.@(Z|bz?(2)|gz|lzma|xz)))))
                   c=(bsdtar xvf);;
            *.7z)  c=(7z x);;
            *.Z)   c=(uncompress);;
            *.bz2) c=(bunzip2);;
            *.exe) c=(cabextract);;
            *.gz)  c=(gunzip);;
            *.rar) c=(unrar x);;
            *.xz)  c=(unxz);;
            *.zip) c=(unzip);;
            *.zst) c=(unzstd);;
            *)     echo "$0: unrecognized file extension: \`$i'" >&2
                   continue;;
        esac

        command "${c[@]}" "$i"
        ((e = e || $?))
    done
    return "$e"
}

Another way to do this is to install a specialized package, see Archiving and compression tools#Convenience tools.

Very often changing to a directory is followed by the ls command to list its contents. Therefore it is helpful to have a second function doing both at once. In this example we will name it cl (change list) and show an error message if the specified directory does not exist.

Of course the ls command can be altered to fit your needs, for example ls -hall --color=auto.

note () {
    # if file doesn't exist, create it
    if [[ ! -f $HOME/.notes ]]; then
        touch "$HOME/.notes"
    fi

    if ! (($#)); then
        # no arguments, print file
        cat "$HOME/.notes"
    elif [[ "$1" == "-c" ]]; then
        # clear file
        printf "%s" > "$HOME/.notes"
    else
        # add all arguments to file
        printf "%s\n" "$*" >> "$HOME/.notes"
    fi
}

Inspired by #Simple note taker

calc() {
    echo "scale=3;$@" | bc -l
}

Kingbash - menu driven auto-completion (see BBS#101010).

Install from the AUR, then insert the following into your ~/.bashrc:

Detailed information on an IP address or hostname in bash via https://ipinfo.io:

ipif() { 
    if grep -P "(([1-9]\d{0,2})\.){3}(?2)" <<< "$1"; then
	 curl ipinfo.io/"$1"
    else
	ipawk=($(host "$1" | awk '/address/ { print $NF }'))
	curl ipinfo.io/${ipawk[1]}
    fi
    echo
}