A collection of useful commands

useful_bash.sh

## Batch rename files
to_replace="REPLACE ME"
replace_with=""
find . -type f -iname "*PATTERN TO MATCH*" -print0 | while IFS= read -r -d $'\0' file; do
    mv "$file" "${file/$to_replace/$replace_with}";
done
# http://stackoverflow.com/questions/15065010/how-to-perform-a-for-each-file-loop-by-using-find-in-shell-bash

# option 2
to_replace="REPLACE ME"
replace_with=""
for file in "*.PATTERN"; do
  mv "$file" "${file/$to_replace/$replace_with}";
done

#-------------------------------------------------------------------------------------------------------------

## Delete 
# files of size 0
find . -type f -size 0 -delete

# symlinks
find . -type l -delete

#-------------------------------------------------------------------------------------------------------------

# b) function cd_func
# This function defines a 'cd' replacement function capable of keeping,
# displaying and accessing history of visited directories, up to 10 entries.
# To use it, uncomment it, source this file and try 'cd --'.
# acd_func 1.0.5, 10-nov-2004
# Petar Marinov, http:/geocities.com/h2428, this is public domain
######### Usage
# cd --
# Shows the history list of visited directories. The list shows the most recently visited names on the top.
#
# cd -NUM
# Changes the current directory with the one at position NUM in the history list. The directory is also moved from this position to the top of the list
cd_func ()
{
  local x2 the_new_dir adir index
  local -i cnt

  if [[ $1 ==  "--" ]]; then
    dirs -v
    return 0
  fi

  the_new_dir=$1
  [[ -z $1 ]] && the_new_dir=$HOME

  if [[ ${the_new_dir:0:1} == '-' ]]; then
    #
    # Extract dir N from dirs
    index=${the_new_dir:1}
    [[ -z $index ]] && index=1
    adir=$(dirs +$index)
    [[ -z $adir ]] && return 1
    the_new_dir=$adir
  fi

  #
  # '~' has to be substituted by ${HOME}
  [[ ${the_new_dir:0:1} == '~' ]] && the_new_dir="${HOME}${the_new_dir:1}"

  #
  # Now change to the new dir and add to the top of the stack
  pushd "${the_new_dir}" > /dev/null
  [[ $? -ne 0 ]] && return 1
  the_new_dir=$(pwd)

  #
  # Trim down everything beyond 11th entry
  popd -n +11 2>/dev/null 1>/dev/null

  #
  # Remove any other occurence of this dir, skipping the top of the stack
  for ((cnt=1; cnt <= 10; cnt++)); do
    x2=$(dirs +${cnt} 2>/dev/null)
    [[ $? -ne 0 ]] && return 0
    [[ ${x2:0:1} == '~' ]] && x2="${HOME}${x2:1}"
    if [[ "${x2}" == "${the_new_dir}" ]]; then
      popd -n +$cnt 2>/dev/null 1>/dev/null
      cnt=cnt-1
    fi
  done

  return 0
}

alias cd=cd_func

#-------------------------------------------------------------------------------------------------------------

extract () {
   if [ -f $1 ] ; then
       case $1 in
           *.tar.bz2)   tar xvjf $1    ;;
           *.tar.gz)    tar xvzf $1    ;;
           *.bz2)       bunzip2 $1     ;;
           *.rar)       unrar x $1       ;;
           *.gz)        gunzip $1      ;;
           *.tar)       tar xvf $1     ;;
           *.tbz2)      tar xvjf $1    ;;
           *.tgz)       tar xvzf $1    ;;
           *.zip)       unzip $1       ;;
           *.Z)         uncompress $1  ;;
           *.7z)        7z x $1        ;;
           *)           echo "don't know how to extract '$1'..." ;;
       esac
   else
       echo "'$1' is not a valid file!"
   fi
 }
 
#-------------------------------------------------------------------------------------------------------------

## Create animations using ImageMagick

# convert *.JPG -coalesce -duplicate 1,-2-1 -quiet -layers OptimizePlus -loop 0 -rotate 90 patrol.gif
# convert *.JPG -rotate 90 animation.gif
for d in ./*/ ;
do
  (cd "$d" && convert *.JPG -coalesce -duplicate 1,-2-1 -quiet -layers OptimizePlus -loop 0 -rotate 90 patrol.gif && convert *.JPG -rotate 90 animation.gif);
done