chmod command


chmod [options] mode(s) filename(s) chmod [options] octal_mode(s) filename(s)

The chmod command is used to change the access mode of files. Only the owner of the file or the superuser may alter its access. There are two methods for expressing the mode you wish to assign. The first is the symbolic method, wherein you specify letters representing the mode. This requires that you specify the following information.

Who is affected:

u User who owns the file
g Group (only users in file’s group)
o Other users
a All (default)

What operation:

+ Add permission
Remove permission
= Set permission, overwriting old permissions

What kind of permission:

r Read
w Write
x Execute
s User or group ID is temporarily replaced with that of the file
t Set sticky bit: keep executable in memory after exit