iankelling.org Git - lnf/blob - lnf

   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 _lnf_existing_link() {
  25   local target dest_file dest_dir
  26   target="$1"
  27   dest_file="$2"
  28   dest_dir="$3"
  29   if [[ -L $dest_file ]]; then
  30     if [[ $(readlink $dest_file) == "$target" ]]; then
  31       # Leave the link in place, but make sure it's
  32       # owner & group is as if we created it.
  33       # links all get 777 perms, so
  34       # we already know that is right.
  35
  36       # test for setgid.
  37       if [[ $(stat -L -c%a "$dest_dir") == 2??? ]]; then
  38         grp=$(stat -L -c%g "$dest_dir") || return $?
  39       else
  40         grp=$(id -g) || return $?
  41       fi
  42       if [[ $EUID == 0 && $(stat -c%u "$dest_file") != 0 ]]; then
  43         chown -h 0:$grp "$dest_file" || return $?
  44       elif [[ $(stat -c%g "$dest_file") != "$grp" ]]; then
  45         chgrp -h $grp "$dest_file" || return $?
  46       fi
  47       do_exit=true
  48       return 0
  49     fi
  50     to_remove+=("$dest_file")
  51   elif [[ -e $dest_file ]]; then
  52     to_remove+=("$dest_file")
  53   fi
  54   to_link+=("$target")
  55 }
  56 lnf() {
  57   local help="Usage:
  58        lnf [OPTIONS] -T TARGET LINK_NAME     (1st form)
  59        lnf [OPTIONS] TARGET                  (2nd form)
  60        lnf [OPTIONS] TARGET... DIRECTORY     (3rd form)
  61 Create symlinks forcefully
  62
  63 If the link already exists, make it's ownership be the same as if it was
  64 newly created (only chown if we are root).  Removes existing files using
  65 rm -rf. Create directory of link if needed. Slightly more restrictive
  66 arguments than ln.
  67
  68 In the 1st form, create a link to TARGET with the name LINK_NAME.  In the 2nd
  69 form, create a link to TARGET in the current directory.  In the 3rd form, create
  70 links to each TARGET in DIRECTORY.
  71
  72 -n|--dry-run     Do verbose dry run.
  73 -v|--verbose     Print commands which modify the filesystem.
  74 -h|--help        Print help and exit.
  75 "
  76
  77
  78   local temp nodir
  79   local verbose=false
  80   local dry_run=false
  81   local do_exit=false
  82   temp=$(getopt -l help,dry-run,verbose hnTv "$@") || usage 1
  83   eval set -- "$temp"
  84   while true; do
  85     case $1 in
  86       -n|--dry-run) dry_run=true; verbose=true; shift ;;
  87       -T) nodir=-T; shift ;;
  88       -v|--verbose) verbose=true; shift ;;
  89       -h|--help) echo "$help"; return 0 ;;
  90       --) shift; break ;;
  91       *) echo "$0: Internal error! unexpected args: $*" ; exit 1 ;;
  92     esac
  93   done
  94
  95   if (( $# == 0 )); then
  96     echo "$help"
  97     return 1
  98   fi
  99
 100   if [[ $nodir ]]; then
 101     if (( $# != 2 )); then
 102       echo "lnf: error: expected 2 arguments with -T flag. Got $#"
 103       return 1
 104     fi
 105   fi
 106
 107   local reset_extglob=false
 108   ! shopt extglob >/dev/null && reset_extglob=true
 109   shopt -s extglob
 110
 111
 112   local -a to_remove to_link
 113   local ret prefix dest_dir grp target
 114   local mkdir=false
 115
 116   if [[ $nodir ]]; then
 117     dest_file="$2"
 118     dest_dir="$(dirname "$dest_file")"
 119     _lnf_existing_link "$1" "$dest_file" "$dest_dir" || return $?
 120     if $do_exit; then return 0; fi
 121     if [[ ! -d $dest_dir ]]; then
 122       mkdir=true
 123       if [[ -e $dest_dir || -L $dest_dir ]]; then
 124         to_remove+=("$dest_dir")
 125       fi
 126     fi
 127     to_link+=("$dest_file")
 128   elif (( $# >= 2 )); then
 129     dest_dir="${!#}"
 130     if [[ -d $dest_dir ]]; then
 131       prefix="$dest_dir" # last arg
 132       for target in "${@:1:$(( $# - 1 ))}"; do # all but last arg
 133         # Remove 1 or more trailing slashes, using.
 134         dest_file="${target%%+(/)}"
 135         # remove any leading directory components, add prefix
 136         dest_file="$prefix/${target##*/}"
 137         _lnf_existing_link "$target" "$dest_file" "$dest_dir"
 138       done
 139     else
 140       to_link+=("${@:1:$(( $# - 1 ))}")
 141       mkdir=true
 142     fi
 143     if (( ${#to_link[@]} == 0 )); then
 144       return 0
 145     fi
 146     to_link+=("$dest_dir")
 147   elif  [[ $# -eq 1 ]]; then
 148     dest_file="${1##*/}"
 149     _lnf_existing_link "$1" "$dest_file" . || return $?
 150     if $do_exit; then return 0; fi
 151   fi
 152   if (( ${#to_remove[@]} >= 1 )); then
 153     if $verbose; then
 154       echo "lnf: rm -rf -- ${to_remove[*]}"
 155     fi
 156     if ! $dry_run; then
 157       rm -rf -- "${to_remove[@]}"
 158     fi
 159   fi
 160
 161   $reset_extglob && shopt -u extglob
 162
 163   if $mkdir; then
 164     if $verbose; then
 165       echo "lnf: mkdir -p $dest_dir"
 166     fi
 167
 168     if ! $dry_run && ! mkdir -p "$dest_dir"; then
 169       echo "lnf error: failed to make directory $dest_dir"
 170       return 1
 171     fi
 172   fi
 173
 174   if $verbose; then
 175     echo "lnf: ln -s $nodir -- ${to_link[*]}"
 176   fi
 177   if ! $dry_run; then
 178     ln -s $nodir -- "${to_link[@]}"
 179   fi
 180 }
 181 lnf "$@"