Shell Programming and Scripting

for file in *.type; do
       awk 'NR==1 {$0=replace} 1' replace=">mm200" $file >tmpfile && mv -f tmpfile $file
done

# VITAL:  Back up first!  Otherwise one typo could mangle all your input files
# and make you very sad.
tar -cf type-backup.tar *.type

for file in *.type; do
       awk 'NR==1 {$0=replace} 1' replace=">mm200" "$file" > tmpfile
       # Using cat instead of mv means $file will not change ownership
       # or permissions by accident.  This is because it overwrites the file,
       # rather than deleting it and putting a brand-new file in its place.
       cat tmpfile > "$file"
done

rm -f tmpfile

awk '{if(NR==1)$0=replace; print > FILENAME}' replace=">mm200" *.type