replaceit.sh

#!/bin/bash

# This replace spaces in a file name
# with underscores as the default.
# replaceit 
# file 1.txt will be file_1.txt 
# You can provide an argument for replacement. 
# replaceit -
# file-1.txt will be file_1.txt 
# replaceit -f -
# This will replace this-file-1.md to this_file_1.md
# replaceit -f - -t x
# his will replace this-file-1.md to thisxfilex1.md


usage()
{
    echo "Usage: $0 [ -m FROM ] [ -t TO ]"
    exit 2
}


###################
# main script

unset FROM TO

# set defaults
TO="_"
FROM=" "

while getopts "f:t:?h" opt; do
    case $opt in
    f) FROM=$OPTARG ;;
    t) TO=$OPTARG ;;
    h|*) usage ;;
    esac
done


echo "We are replacing $FROM to ${TO}."


for f in *
do
  new="${f//$FROM/$TO}"
  echo "$new"
  if [ "$new" != "$f" ]; then
    if [ -e "$new" ]; then
      echo "Not renaming $f because $new already exists"
    else
      echo "Moving $f to ${new}."
    mv "$f" "$new"
    fi
  fi
done