replace

#!/bin/bash -

usage() {
  cat <<EOF
Usage:
  $(basename -- "$0") [options] <search> <replace> <file> ...

Rename the <file>(s) by replacing <search> (glob pattern)
by <replace>.

Options:
  -c - copy
    Do not rename the file, but create a copy.

  -f - force
    Overwrite existing files.

  -g - global
    Replace globally (default is just the first time).

  -h - help
    Print help message and exit.

  -n - dry run
    Do not move/copy any files, only print what would happen.

  -v - verbose
    Print what happens.
EOF
}

warn() {
  printf >&2 '%s\n' "$1"
}

missing_argument() {
  warn "Missing argument for '$1'."
  exit 2
}

if [ $# -eq 0 ]; then
  usage >&2
  exit 1
fi

args=()
copy=0
dryrun=0
force=0
help=0
replace_globally=0
verbose=0

OPTSTRING=':cfghnv'
while getopts ${OPTSTRING} opt; do
  case ${opt} in
    c)
      copy=1
      ;;
    f)
      force=1
      ;;
    g)
      replace_globally=1
      ;;
    h)
      help=1
      ;;
    n)
      dryrun=1
      ;;
    v)
      verbose=1
      ;;
    ?)
      echo >&2 "Invalid option: -${OPTARG}."
      exit 1
      ;;
  esac
done
shift $((OPTIND-1))

if (( help )); then
  usage
  exit 0
fi

if (( "$#" < 3 )); then
  usage >&2
  exit 1
fi

search_string=$1
replace_string=$2
shift 2

cmd='mv'
arrow='->'
if (( copy )); then
  cmd='cp'
  arrow='+>'
fi
cmdarr=( "$cmd")
if (( force )); then
  cmdarr+=('-f')
fi
cmdarr+=('--')

for file; do
  if [[ $search_string == '^' ]]; then
    new="${replace_string}${file}"
  elif [[ $search_string == '$' ]]; then
    new="${file}${replace_string}"
  elif (( replace_globally )); then
    new=${file//$search_string/$replace_string}
  else
    new=${file/$search_string/$replace_string}
  fi
  if [[ $new == $file ]]; then
    warn "Name unchanged for '$file', skipping."
    continue
  fi
  if (( dryrun )); then
    printf '%s %s %s' "$file" "$arrow" "$new"
    if [[ -f "$new" ]]; then
      printf '%s' ' (file exists!)'
    fi
    printf '\n'
    continue
  fi
  if [[ -f "$new" ]] && ! (( force )); then
    warn "Not ${cmd}-ing '${file}' to '${new}', target file exists already (use -f to overwrite)."
    continue
  fi
  "${cmdarr[@]}" "$file" "$new"
  if [[ $? -eq 0 ]]; then
    (( verbose )) && printf '%s %s %s\n' "$file" "$arrow" "$new"
  else
    warn "Cannot ${cmd} '${file}' to '${new}'."
  fi
done