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chmod

When it is necessary to modify the permissions on a particular file or group

of files this command is the one to use. It takes the form:

chmod   

 has the form: [ugoa...][[+ =][rwxXstugo...]...][,...]

u

the user who owns the file

g

users in the files group

o

other users not in the group

a

all users

+

causes permissions to be added to those already present

for the file.

remove the specified permissions from the file

=

make those permissions specified as the only permissions

defined for the file.

r

read permission

w

write permission

x

executed permission

X

execute only if the file is a directory or already has per 

mission for some user.

s

set user or group id on execution.

t

save program text on swap device

u

set the permission to those of the user who owns the file.