iankelling.org Git - distro-setup/blob - path-add-function

   1 #!/bin/bash
   2 # I, Ian Kelling, follow the GNU license recommendations at
   3 # https://www.gnu.org/licenses/license-recommendations.en.html. They
   4 # recommend that small programs, < 300 lines, be licensed under the
   5 # Apache License 2.0. This file contains or is part of one or more small
   6 # programs. If a small program grows beyond 300 lines, I plan to switch
   7 # its license to GPL.
   8
   9 # Copyright 2024 Ian Kelling
  10
  11 # Licensed under the Apache License, Version 2.0 (the "License");
  12 # you may not use this file except in compliance with the License.
  13 # You may obtain a copy of the License at
  14
  15 #     http://www.apache.org/licenses/LICENSE-2.0
  16
  17 # Unless required by applicable law or agreed to in writing, software
  18 # distributed under the License is distributed on an "AS IS" BASIS,
  19 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  20 # See the License for the specific language governing permissions and
  21 # limitations under the License.
  22
  23
  24
  25 # avoiding bashisms so it can be used in edge cases where I don't have bash,
  26 # however, I'm not super confident that I've avoided them all
  27 #
  28 path-add() {
  29   local help="usage: path_add [options] PATH...
  30 --help:     print this
  31 --end:      adds to end of path, which will give it lowest priority
  32 --ifexists: add to path only if directory exists"
  33   local found x y ifexists end loop newpath
  34   ifexists=false
  35   end=false
  36   loop=true
  37   # portable substring matching is ugly http://mywiki.wooledge.org/BashFAQ/041
  38   while $loop; do
  39     case $1 in
  40       --*)
  41         if [ "$1" = --end ]; then
  42           end=true
  43         elif [ "$1" = --ifexists ]; then
  44           ifexists=true
  45         elif [ "$1" = --help ]; then
  46           echo "$help"
  47           return
  48         fi
  49         shift
  50         ;;
  51       *)
  52         loop=false
  53         ;;
  54     esac
  55   done
  56   # if we arent passed a PATH, just return 0 for convenience
  57   if ! test "$1"; then
  58     return 0
  59   fi
  60   IFS=:
  61   # build up the path without the components we want to add
  62   for y in $PATH; do
  63     for x in "$@"; do
  64       if [ "$x" = "$y" ]; then
  65         found=true
  66       else
  67         found=false
  68       fi
  69     done
  70     if ! $found; then
  71       if [ ! "$newpath" ]; then
  72         newpath="$y"
  73       else
  74         newpath="$newpath:$y"
  75       fi
  76     fi
  77   done
  78
  79   unset IFS
  80   PATH="$newpath"
  81   for x in "$@"; do
  82     if ! $ifexists || [ -d "$x" ]; then
  83       if [ ! "$PATH" ]; then
  84         PATH="$x"
  85       elif $end; then
  86         PATH="$PATH:$x"
  87       else
  88         PATH="$x:$PATH"
  89       fi
  90     fi
  91   done
  92 }