arrayutil

#!/bin/bash

# without removes a component from its argument array, echoing the new array
# joined by IFS.  For Example:
#
#   $ PATH=/bin:/usr/bin:/usr/local/bin
#   $ IFS=:; without /usr/local/bin $PATH
#   /bin:/usr/bin
without()
{
    arg="$1"
    shift
    out=()
    for part in "$@"; do
        if [ -n "$part" ] && [ "$part" != "$arg" ]; then
            out+=($part)
        fi
    done
    echo "${out[*]}"
}

# prepend adds a component to the head of its argument array, echoing the new
# array joined by IFS; the given component is deduped, and ensured to now come
# first.  For example:
#
#   $ PATH=/bin:/usr/bin:/usr/local/bin
#   $ PATH=$(IFS=:; prepend /usr/local/bin $PATH)
#   $ echo $PATH
#   /usr/local/bin:/bin:/usr/bin
#
#   $ PATH=$(IFS=:; prepend $HOME/bin $PATH)
#   $ echo $PATH
#   /home/bob/bin:/usr/local/bin:/bin:/usr/bin
prepend()
{
    arg="$1"
    shift
    out=($arg)
    for part in "$@"; do
        if [ -n "$part" ] && [ "$part" != "$arg" ]; then
            out+=($part)
        fi
    done
    echo "${out[*]}"
}

# append adds a component to the tail of its argument array, echoing the new
# array joined by IFS; the given component is deduped, and ensured to now come
# last.  For example:
#
#   $ PATH=/bin:/usr/bin:/usr/local/bin
#   $ PATH=$(IFS=:; prepend /usr/local/bin $PATH)
#   $ echo $PATH
#   /bin:/usr/bin:/usr/local/bin
#
#   $ PATH=$(IFS=:; prepend $HOME/bin $PATH)
#   $ echo $PATH
#   /bin:/usr/bin:/usr/local/bin:/home/bob/bin
append()
{
    arg="$1"
    shift
    out=()
    for part in "$@"; do
        if [ -n "$part" ] && [ "$part" != "$arg" ]; then
            out+=($part)
        fi
    done
    out+=($arg)
    echo "${out[*]}"
}