Unix command to insert a comment on the top of all files in a directory

Question

I want to add a comment to all files in a directory in Unix. Please suggest a solution if there is any combination of commands I can use.

Answer 1

Using find and sed:

$ find . -maxdepth 1 -type f -exec sed -i '1i #comment' {} \;

This will add the line #comment to the top of all the files in the current directory

Answer 2

Try doing this using a simple shell concatenation :

for i in *; do
    { echo '# this is a comment'; cat "$i"; } > /tmp/_$$file &&
    mv /tmp/_$$file "$i"
done

Answer 3

For the fun, try doing this using ed :

echo $'1i\n# comment\n.\nw\nq' | ed -s file.txt 

Here-doc version :

ed -s file.txt <<EOF
1i
# comment
.
w
q
EOF

Answer 4

If you want to add a comment to all files with an extension (e.g. ".rb"):

find . -maxdepth 1 -type f -name "*.rb" -exec sed -i '1i #comment' {} \;

And recursive:

find . -type f -name "*.rb" -exec sed -i '1i #comment' {} \;