Changing file permissions recursively

Every now and then you’ve got a massive directory tree whose reading permissions need to be changed. For example, all files readable to all users, all directories accessible to all users, all executables executable by all users.

This is easy enough to do with find and chmod commands. Assuming that the root of the directory tree is somedir:

Set all directories to rwxr-xr-x (a.k.a. 755)
find somedir -type d -print -exec chmod 755 {} \;

Make all files readable
find somedir -type f -print -exec chmod go+r {} \;

Change all 744 files, executable by the owner, to 755, executable by all:
find somedir -type f -perm 744 -print -exec chmod 755 {} \;