Creating a bash script to change file names to lower case - bash

Question

I am trying to write a bash script that convert all file names to lowercase, but I have a problem because it does not work for one case.
When you have your file1 and FILE1, and you will use it on the FILE1 it will replace letters file1.
#!/bin/bash
testFILE=""
FLAG="1"
for FILE in *
do
testFILE=`echo FILE | tr '[A-Z]' '[a-z]'`
for FILE2 in *
do
if [ `echo $testFILE` = `echo $FILE2` ]
then
FLAG="0"
fi
done
if [ $FLAG = "1" ]
then
mv $FILE `echo $FILE | tr '[A-Z]' '[a-z]'`
fi
FLAG="1"
done

Answer 1

Looks like
testFILE=`echo FILE | tr '[A-Z]' '[a-z]'`
should be
testFILE=`echo "$FILE" | tr '[A-Z]' '[a-z]'`
Re-writing your script to fix some other minor things
#!/bin/bash
testFILE=
FLAG=1
for FILE in *; do
testFILE=$(tr '[A-Z]' '[a-z]' <<< "$FILE")
for FILE2 in *; do
if [ "$testFILE" = "$FILE2" ]; then
FLAG=0
fi
done
if [ $FLAG -eq 1 ]; then
mv -- "$FILE" "$(tr '[A-Z]' '[a-z]' <<< "$FILE")"
fi
FLAG=1
done
Quote variables to prevent word-splitting ("$FILE" instead of $FILE)
Generally preferable to use $() instead of tildes
Don't use string comparison where you don't have to
Use -- to delimit arguments in commands that accept it (in order to prevent files like -file from being treated as options)
By convention, you should really only use capital variable names for environment variables, though I kept them in above.
Pipes vs here strings (<<<) doesn't matter so much here, but <<< is slightly faster and generally safer.
Though more simply, I think you want
#!/bin/bash
for file in *; do
testFile=$(tr '[A-Z]' '[a-z]' <<< "$file")
[ -e "$testFile" ] || mv -- "$file" "$testFile"
done
Or on most modern mv implementations (not technically posix)
#!/bin/bash
for file in *; do
mv -n -- "$file" "$(tr '[A-Z]' '[a-z]' <<< "$file")"
done
From the man page
-n, --no-clobber
do not overwrite an existing file

Answer 2

Below script :
find . -mindepth 1 -maxdepth 1 -print0 | while read -d '' filename
do
if [ -e ${filename,,} ]
then
mv --backup ${filename} ${filename,,} 2>/dev/null
# create a backup of the desination only if the destination already exist
# suppressing the error caused by moving the file to itself
else
mv ${filename} ${filename,,}
fi
done
may do the job for you.
Advantages of this script
It will parse files containing newlines.
It avoids a prompt by doing selective backup destination that already exists.