path-tools.sh

#!/usr/bin/env bash

path_append() {
  [[ -n $1 && $# -eq 1 ]] || { printf "Usage: path_append ELM\n" >&2; return 1; }
  local new_path; new_path=$(path_remove "$1")
  printf "%s\n" "$new_path:$1"
}

path_prepend() {
  [[ -n $1 && $# -eq 1 ]] || { printf "Usage: path_prepend ELM\n" >&2; return 1; }
  local new_path; new_path=$(path_remove "$1")
  printf "%s\n" "$1:$new_path"
}

path_insert_after() {
  local new_path new_path_inner path rev_path prepend=false matched=false
  if [[ $1 == '-p' ]]; then prepend=true; shift; fi
  [[ -n $1 && $# -le 2 ]] || { printf "Usage: path_insert_after [-p] ELM [GLOB]\n" >&2; return 1; }
  if [[ -n $2 ]]; then
    new_path=$(path_remove "$1")
    while IFS= read -r -d ':' rev_path; do
      path=$(rev <<<"$rev_path")
      # shellcheck disable=2053
      if [[ ${path%/} != $2 ]] || $matched; then
        new_path_inner=$new_path_inner:$rev_path
      else
        new_path_inner=$new_path_inner:$(rev <<<"$1"):$rev_path
        matched=true
      fi
    done < <(rev <<<":$new_path")
    new_path_inner=$(rev <<<"$new_path_inner")
    new_path=${new_path_inner%:}
    if ! $matched; then
      if $prepend; then new_path=$1:$new_path
      else new_path=$new_path:$1; fi
    fi
    printf "%s\n" "$new_path"
  else
    if $prepend; then path_prepend "$1"
    else path_append "$1"; fi
  fi
}

path_insert_before() {
  local new_path new_path_inner path prepend=false matched=false
  if [[ $1 == '-p' ]]; then prepend=true; shift; fi
  [[ -n $1 && $# -le 2 ]] || { printf "Usage: path_insert_before [-p] ELM [GLOB]\n" >&2; return 1; }
  if [[ -n $2 ]]; then
    new_path=$(path_remove "$1")
    while IFS= read -r -d ':' path; do
      # shellcheck disable=2053
      if [[ ${path%/} != $2 ]] || $matched; then
        new_path_inner=$new_path_inner:$path
      else
        new_path_inner=$new_path_inner:$1:$path
        matched=true
      fi
    done <<<"$new_path:"
    new_path=${new_path_inner#:}
    if ! $matched; then
      if $prepend; then new_path=$1:$new_path
      else new_path=$new_path:$1; fi
    fi
    printf "%s\n" "$new_path"
  else
    if $prepend; then path_prepend "$1"
    else path_append "$1"; fi
  fi
}

path_remove() {
  [[ -n $1 && $2 =~ ^|true|false$ && $# -le 2 ]] || { printf "Usage: path_remove ELM [ENABLE_GLOB]\n" >&2; return 1; }
  local path new_path
  while IFS= read -r -d ':' path; do
    # shellcheck disable=2053
    if [[ $2 = true && ${path%/} != $1 ]] || [[ $2 != true && ${path%/} != "${1%/}" ]]; then
      new_path=$new_path:$path
    fi
  done <<<"$PATH:"
  printf "%s\n" "${new_path#:}"
}

path_contains() {
  [[ -n $1 || ! $2 =~ ^|true|false$ && $# -le 2 ]] || { printf "Usage: path_contains ELM [ENABLE_GLOB]\n" >&2; return 1; }
  local path
  while IFS= read -r -d ':' path; do
    # shellcheck disable=2053
    if [[ $2 = true && ${path%/} = $1 ]] || [[ $2 != true && ${path%/} = "${1%/}" ]]; then
      return 0
    fi
  done <<<"$PATH:"
  return 1
}

# shellcheck disable=2120
path_validate() {
  [[ $# -eq 0 ]] || { printf "Usage: path_validate\n" >&2; return 1; }
  local ret=0
  if [[ $PATH = *'\0'* ]]; then
    printf "path-tools.sh: \$PATH contains nul bytes\n" >&2
    ret=1
  fi
  if [[ $PATH =~ ^:|:$|:: ]]; then
    printf "path-tools.sh: \$PATH contains empty strings\n" >&2
    ret=1
  fi
  local duplicates=(); IFS=$'\n' readarray -t duplicates < <(tr ':' $'\n' <<<"$PATH" | sed 's%\(.\)/$%\1%' | sort | uniq -D | uniq)
  if [[ ${#duplicates[@]} -ne 0 ]]; then
    printf "path-tools.sh: \$PATH contains duplicate paths:\n" >&2
    printf "  %s\n" "${duplicates[@]}" >&2
    ret=1
  fi
  return $ret
}