How can I convert tabs to spaces in every file of a directory?

Question

How can I convert tabs to spaces in every file of a directory (possibly recursively)?

Also, is there a way of setting the number of spaces per tab?

Answer 1

Collecting the best comments from Gene's answer, the best solution by far, is by using sponge from moreutils.

sudo apt-get install moreutils
# The complete one-liner:
find ./ -iname '*.java' -type f -exec bash -c 'expand -t 4 "$0" | sponge "$0"' {} \;

Explanation:

• ./ is recursively searching from current directory
• -iname is a case insensitive match (for both *.java and *.JAVA likes)
• type -f finds only regular files (no directories, binaries or symlinks)
• -exec bash -c execute following commands in a subshell for each file name, {}
• expand -t 4 expands all TABs to 4 spaces
• sponge soak up standard input (from expand) and write to a file (the same one)*.

NOTE: * A simple file redirection (> "$0") won't work here because it would overwrite the file too soon.

Advantage: All original file permissions are retained and no intermediate tmp files are used.