[SOLVED] Bash script to remove leading zeros in file name

Issue

My task is easy enough to accomplish in python, but I am trying to do it with a Bash script.

I have files named [0001-9999].jpg (i.e, always 4 digits long; e.g, 0003.jpg, 4003.jpg) in two different directories, 'left' & 'right' (corresponding to left and right-page bindings of a scanned book). I want to combine the two directories, in ascending order such that they are named [1-19998].jpg in a new 'output' directory.

I am stuck at getting my Bash script to recreate the filename format (always 4-digits, ranging from 0001 to 9999) so that I can cp them to 'output'.

Here is what I have so far in combine.sh:

#!/bin/bash

# combine.sh assumes it is copied into intended directory, and all files are in order and present. 
# verso (left page) folder is called 'left', recto (right page) folder is called 'right'.
# first (and only) argument should be the word 'left' or 'right' in lower-caps, for first page.

# get total number of pages
l=`ls -l left | wc -l`
r=`ls -l right | wc -l`
size=$(( ($l - 1) + ($r - 1) ))

# set $first offset based on input
if [ "$1" == "left" ]
then
    first=0
  elif [ "$1" == "right" ]
then
    first=1
else
    echo invalid first
fi

# loop to copy files
j=1
for (( i=1 ; i<=$size; i++ ));
do
    # alternate between left and right, starting w/ $1
    # copying into ./output/ with new name [i].jpg
    dir=$(( (i + 1 + first) % 2 )) # offset for left or right
    if [ $dir -eq 0 ]
    then
        echo should be 000$j.jpg 
        # move/copy next jpg of verso dir into combined dir
      elif [ $dir -eq 1 ]
    then
        (( j += 1 ))
        # move/copy next jpg of recto dir into combined dir
    fi
done

Clearly, my current model wouldn't work past 0009.jpg. It is the last piece of this script (just need to cp after) though, and any help would be greatly appreciated! I'm guessing I need to do some awk-ing on the input filename strings?

Solution

You're looking for something like this:

case $1 in
left) dir2=right ;;
right) dir2=left ;;
*) # TODO handle bad argument
esac
dir1=$1

n=0
for src1 in "$dir1"/*.jpg; do
  echo mv "$src1" "output/$((n+=1)).jpg"

  src2=$dir2${src1#"$dir1"}
  if test -e "$src2"; then
    echo mv "$src2" "output/$((n+=1)).jpg"
  else
    break
  fi
done

Remove echos if the output looks good.

Answered By - oguz ismail

Answer Checked By - Senaida (WPSolving Volunteer)