Chown

chown changes the user and/or group ownership of a file or directory.

Examples:

Change the owner:
chown bob myfile.txt Changes the owner of myfile.txt to bob

Change the group:
chown :office myfile.txt Change just the group of myfile.txt to office.

Change the owner and the group:
chown bob:office myfile.txt Change the owner of myfile.txt to bob, and change the group to office

Change the owner and group (shortcut):
chown bob. myfile.txt Change the owner of myfile.txt to bob, and change the group to the bob group.

Change the owner and group for a directory, and all files and directories below it:
chown -R bob. /home/bob/workf

References

1. chown man page