NAME

chmod − change mode of file

SYNOPSIS

chmod(name, mode)
char *name;
int mode;

DESCRIPTION

The file whose name is given as the null-terminated string pointed to by name has its mode changed to mode. Modes are constructed by oring together some combination of the following:

04000 set user ID on execution

02000 set group ID on execution

01000 save text image after execution (for shareable files)

00400 read by owner

00200 write by owner

00100 execute (search on directory) by owner

00070 read, write, execute (search) by group

00007 read, write, execute (search) by others

If an executable file is set up for sharing (see the cc −n option), then mode 1000 prevents the system from abandoning the swap-space image of the program-text portion of the file when its last user terminates.  Ability to set this bit is restricted to the super-user since swap space is consumed by the images. 

Only the owner of a file (or the super-user) may change the mode.  Only the super-user can set the 1000 mode. 

Changing the owner of a file turns off the set-user-id bit.  This makes the system somewhat more secure by protecting set-user-id files from remaining set-user-id if they are modified, at the expense of a degree of compatibility. 

SEE ALSO

chmod(1)

DIAGNOSTIC

Zero is returned if the mode is changed; −1 is returned if name cannot be found or if the current user is neither the owner of the file nor the super-user. 

7th Edition  —  1/6/82