Some Linux shell scripts

Search for duplicate files

At first, I present a linux shell script to search for duplicate files based on their content. The idea is to calculate the SHA256 Hash from the file content. If two files have the same SHA256 Hash then they are supposed to be identical.

                        
#! /bin/bash
# usage: dupsearch pattern
# where pattern can be *.jpg or *.png or *.mp3 or something else
# creates 2 temporary files

tmpfile1=$(mktemp /tmp/dupjpg.XXXXXX)
tmpfile2=$(mktemp /tmp/dupjpg.XXXXXX)

# connects the files with filedescriptor 3 and 4
exec 3>"$tmpfile1"
exec 4>"$tmpfile2"

# finds the files, calculates the SHA256-hash and sorts the file
find . -name "$1" 2>/dev/null|xargs sha256sum -b 2>/dev/null|sort >&3 

# the sorted file is in order of the hash codes, but the codes 
# are together with the filenames. cut the codes from the filenames
# and leave only duplicate hash codes. save them to file tmpfile2
cut -d ' ' -f 1 "$tmpfile1"|uniq -d >&4

# read the codes from the file and look for the filenames
# the filenames are in in the position beginning after position 67 in 
# the file
grep -f "$tmpfile2" "$tmpfile1" | cut -c 67-

# delete the temporary files and close the filedescriptors
rm "$tmpfile1"
rm "$tmpfile2"
exec 3>&-
exec 4>&-
                        
                    

Display a slideshow from a playlist

This script displays a slideshow from a playlist with filenames, line by line, in a file. The interesting in the file is, that /dev/stdin is opened as a filedescriptor 3 and despite the input for the while loop is redirected to the file from which the playlist is read, one can get keystrokes for read from /dev/stdin. So you have two input streams. The script is else rather straightforward. The pictures are displayed with feh.

                                                      
#! /bin/bash

exec 3< /dev/stdin

read -n 1 -p "Press any key to begin slideshow";
while IFS= read -r line;
do
        echo $line
        feh -g 1024x800 --scale-down $line
        read -n 1 -p "Press any key to continue ^C to exit" <&3
done < $1