How do I compare file names in two directories in shell script?

Question

Right now, this is what my code looks like:

#!/bin/bash

Dir1=$1
Dir2=$2

for file1 in $Dir1/*; do
    for file2 in $Dir2/*; do
        if [[ $file1 == $file2 ]]; then
            echo "$file1 is contained in both directories"
        fi
    done
done

I am trying to compare the file names of the two directories entered and say that the file is in both directories if the filename matches. When I try to run it though, nothing is echo-ed even though I have the same file in both directories.

Answer 1

Files that are in both Dir1 and Dir2:

find "$Dir1/" "$Dir2/" -printf '%P\n' | sort | uniq -d

Files that are in Dir1 but not in Dir2:

find "$Dir1/" "$Dir2/" "$Dir2/" -printf '%P\n' | sort | uniq -u

Files that are in Dir2 but not in Dir1:

find "$Dir1/" "$Dir1/" "$Dir2/" -printf '%P\n' | sort | uniq -u

Answer 2

If you want to know what's common to two directories then this is another way with much less coding.

#!/bin/bash

comm -12 <(ls -F $1) <(ls -F $2)

See man comm for more information about the comm utility.

Answer 3

It doesn't work because you're comparing variables that contain the directory prefix. Just remove the prefix before comparing:

name1=${file1##*/}
name2=${file2##*/}
if [[ $name1 == $name2 ]]; then
    echo "$name1 exists in both directories"
fi

Also, nested loops seems like an inefficient way to do this. You just need to get the filenames from one directory, and use a simple file existence check for the other directory.

for file in $Dir1/*; do
    name=${file##*/}
    if [[ -f $Dir2/$name ]]; then
        echo "$name exists in both directories"
    fi
done

Answer 4

I just tested this and it worked:

DIR1=$(ls dir1)
DIR2=$(ls dir2)

for i in $DIR1; do
    for j in $DIR2; do
        if [[ $i == $j ]]; then
            echo "$i == $j"
        fi
    done
done

Answer 5

Your comparison fails because Dir1/foo is not the same as Dir2/foo. Instead, if you change to one directory, your * will expand to just the filenames:

#!/bin/bash

Dir1="$1"
Dir2="$2"

if ! cd "$Dir1"; then
  echo "ERROR: Couldn't find directory $Dir1" >&2
  exit 1
fi

if [[ ! "$Dir2" =~ ^/ ]]; then
  echo "ERROR: Second directory must be a full path." >&2
  exit 1
fi

for file1 in *; do
    if [ -f "$Dir2/$file1" ]; then
        echo "$file1 is contained in both directories"
    fi
done

Note that this only matches file names. If you want to make sure it's really the same file, you should use cmp to compare them.