A library of usefull BASH 4+ functions (many won't work in sh)

bash-lib.sh

# Please, check https://github.com/dylanaraps/pure-bash-bible
# It is a great chest of treasures

########   STRINGS   #############

# check if elemet is in the ARRAY
# Usage:
# arr=(a b x)
# containsElement 'x' arr
containsElement () {
  local ee=$(shopt -po errexit)
  set +e
  local e match="$1"
  shift
  for e; do
    if [[ "$e" == "$match" ]]; then
      $ee # restore builtin
      return 0
    fi
  done
  $ee # restore builtin
  return 1
}

# Trim spaces from string head and tail
# Usage:
# trim_string "   example   string    "
trim_string() {
    : "${1#"${1%%[![:space:]]*}"}"
    : "${_%"${_##*[![:space:]]}"}"
    printf '%s\n' "$_"
}

# Trim ALL spaces
# shellcheck disable=SC2086,SC2048
# Usage: trim_all "   example   string    "
trim_all() {
    set -f
    set -- $*
    printf '%s\n' "$*"
    set +f
}

# Trim quotes from string
# Usage: trim_quotes "string"
trim_quotes() {
    : "${1//\'}"
    printf '%s\n' "${_//\"}"
}
# Split a string by delimiter
# Usage: split "string" "delimiter" ARRAY_NAME
split(){
  IFS="$2" read -ra $3 <<< "$1"
}

########   ARRAYS   #############

# Usage: reverse_array "array"
reverse_array() {
    shopt -s extdebug
    f()(printf '%s\n' "${BASH_ARGV[@]}"); f "$@"
    shopt -u extdebug
}

# Usage: remove_array_dups "array"
remove_array_dups() {
    declare -A tmp_array

    for i in "$@"; do
        [[ $i ]] && IFS=" " tmp_array["${i:- }"]=1
    done

    printf '%s\n' "${!tmp_array[@]}"
}


########   JUST USEFUL   #############

# Usage: get_term_size
get_term_size() {
    # (:;:) is a micro sleep to ensure the variables are
    # exported immediately.
    shopt -s checkwinsize; (:;:)
    printf '%s\n' "$LINES $COLUMNS"
}

# Sleep without external command (useful for short sleeps)
#        read_sleep 0.2
read_sleep() {
    read -rt "$1" <> <(:) || :
}

# Usage: hex_to_rgb "#FFFFFF"
#        hex_to_rgb "000000"
hex_to_rgb() {
    : "${1/\#}"
    ((r=16#${_:0:2},g=16#${_:2:2},b=16#${_:4:2}))
    printf '%s\n' "$r $g $b"
}

# Generate UUID
uuid() {
    C="89ab"

    for ((N=0;N<16;++N)); do
        B="$((RANDOM%256))"

        case "$N" in
            6)  printf '4%x' "$((B%16))" ;;
            8)  printf '%c%x' "${C:$RANDOM%${#C}:1}" "$((B%16))" ;;

            3|5|7|9)
                printf '%02x-' "$B"
            ;;

            *)
                printf '%02x' "$B"
            ;;
        esac
    done

    printf '\n'
}

# Print a progress bar
# Usage: bar 1 10 [optional bar symbol, default is '-']
#            ^----- Elapsed Percentage (0-100).
#               ^-- Total length in chars. (not includes brackets!)
bar() {
    local b=${3:--}
    ((elapsed=$1*$2/100))

    # Create the bar with spaces.
    printf -v prog  "%${elapsed}s"
    printf -v total "%$(($2-elapsed))s"

    printf '%s' "[${prog// /$b}${total}]"
}

# Prints an integer with suffix (K,M,G,etc)
# does not support fractions like 1500 -> 1.5K, always cuts (1500 -> 1K)
#
with_suffix(){
    awk '{ suffix=" KMGT"; for(i=1; $1>1024 && i < length(suffix); i++) $1/=1024; print int($1) substr(suffix, i, 1), $3; }' <<<${1:-0}
}