Here. By Mayank Sarup.
What do “read”/”write”/”execute” mean?
r – Read permission. Whether the file may be read. In the case of a
directory, this would mean the ability to list the contents of the
w – Write permission. Whether the file may be written to or modified. For
a directory, this defines whether you can make any changes to the contents
of the directory. If write permission is not set then you will not be able
to delete, rename or create a file.
x – Execute permission. Whether the file may be executed. In the case of a
directory, this attribute decides whether you have permission to enter,
run a search through that directory or execute some program from that
Examples of and related commands
chmod u-x,g+w,o+rw somefile
chmod xyz filename
(r = 4; w = 2; x = 1)
chown new-owner somefile
chgrp new-grp somefile