Bash/Functions

Bash also supports functions. Add the functions to ~/.bashrc, or a separate file which is sourced from ~/.bashrc. More Bash function examples can be found in BBS#30155.

Display error codes

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

Compile and execute a C source on the fly

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;
}

Extract

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|zst)))))
                   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"
}

Note: Make sure extglob is enabled: shopt -s extglob, by adding it to the ~/.bashrc (see gregswiki:glob#Options which change globbing behavior).

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

cd and ls in one

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.

cl() {
	local dir="$1"
	local dir="${dir:=$HOME}"
	if [[ -d "$dir" ]]; then
		cd "$dir" >/dev/null; ls
	else
		echo "bash: cl: $dir: Directory not found"
	fi
}

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

Simple note taker

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
}

Simple task utility

Inspired by #Simple note taker

todo() {
    if [[ ! -f $HOME/.todo ]]; then
        touch "$HOME/.todo"
    fi

    if ! (($#)); then
        cat "$HOME/.todo"
    elif [[ "$1" == "-l" ]]; then
        nl -b a "$HOME/.todo"
    elif [[ "$1" == "-c" ]]; then
        > $HOME/.todo
    elif [[ "$1" == "-r" ]]; then
        nl -b a "$HOME/.todo"
        eval printf %.0s- '{1..'"${COLUMNS:-$(tput cols)}"\}; echo
        read -p "Type a number to remove: " number
        sed -i ${number}d $HOME/.todo "$HOME/.todo"
    else
        printf "%s\n" "$*" >> "$HOME/.todo"
    fi
}

Calculator

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

IP info

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
}

Note: Bash is limited to extended regular expressions; this example uses perl regular expressions with grep. [1]