rename each text file according to its first line of text

filename-firstline.sh

#This is a fork of dylan-k code. Only the actual short line to rename inside a loop is changed to a long line.
#Original code gave errors on some special characters. For example if a back slash \ was in the first line to be used as new name.
#Those files were not renamed. This new line ignores those problematic characters and even more, using alphanumeric naming. 
#Many ways to do alpnum renaming are suggested but most actually fail in many cases and bashes and distros.
#This new forked way, alpnum renaming will not fail.
#dylan-k: A shell script that will rename all the text files in a directory
#each file will be named with the first line of text from that file

for file in *
do
   # Avoid renaming diretories!
   if [ -f "$file" ]
   then
       newname=`head -1 $file`
       if [ -f "$newname" ]
       then
              echo "Cannot rename $file to $newname - file already exists"
       else
              mv "$file" $(echo "$newname.txt" | sed -e 's/[^A-Za-z0-9._-]/_/g')
       fi
   fi
done