UNIX Permissions:

chmod
ls -l
chmod u=rwx, g=rx, o=r row*

The wildcard expression row* specifies that the permissions granted in the command applies to all files and directories that start with "row" in the current directory.

w = write
r = read
x = execute

There are a couple different kinds of files with permissions indicated by the first letter of the string:
* '-' : a regular file
* 'd' : a directory - ex: drwx------    4 root     root          138 Sep 23 21:15
* 'l' : a symbolic link
* 'b' : a block device
* 'c' : a character device
* 'p' : a named pipe
* 's' : UNIX domain socket

The difference between a character device and a block device is in how much data a device can take/give to the computer. A character device can give/receive 1 character (one byte) at a time. A block device handles chunks/blocks of data; typically a block is 512 bytes, but it can vary depending on the device.

------
u = user
g = group
o = others
a = all

user,group,other
-r-xr-xr-x    1 root     root     21313888 Sep 29  2001 tiger1.jpg

example: chmod u=rwx,g=rx,o=r row*

To add permissions: "+"
chmod g+w row

To remove permissions: "-"
chmod go-w row