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CHMOD
!!!CHMOD
----
!!NAME


chmod - change permissions of a file
!!SYNOPSIS

 __#include <sys/types.h>__
 __#include <sys/stat.h>__

 __int chmod(const char *__''path''__, mode_t__ ''mode''__);__
!!DESCRIPTION

The mode of the file given by ''path'' is changed.

Modes are specified by ''or'ing'' the following:
|S_ISUID| 04000| set user ID on execution
|S_ISGID| 02000| set group ID on execution
|S_ISVTX| 01000| sticky bit
|S_IRUSR (S_IREAD)| 00400| read by owner
|S_IWUSR (S_IWRITE)| 00200| write by owner
|S_IXUSR (S_IEXEC)| 00100| execute/search by owner
|S_IRGRP| 00040| read by group
|S_IWGRP| 00020| write by group
|S_IXGRP| 00010| execute/search by group
|S_IROTH| 00004| read by others
|S_IWOTH| 00002| write by others
|S_IXOTH| 00001| execute/search by others


The effective UID of the process must be zero or must match the owner of the file.

If the effective UID of the process is not zero and the group of the file does not match the effective group ID of the process or one of its supplementary group IDs, the S_ISGID bit will be turned off, but this will not cause an error to be returned.

Depending on the file system, set user ID and set group ID execution bits may be turned off if a file is written. On some file systems, only the super-user can set the sticky bit, which may have a special meaning. For the sticky bit, and for set user ID and set group ID bits on directories, see stat(2).

On NFS file systems, restricting the permissions will immediately influence already open files, because the access control is done on the server, but open files are maintained by the client. Widening the permissions may be delayed for other clients if attribute caching is enabled on them.

!!RETURN VALUE
On success, zero is returned. On error, -1 is returned, and ''errno'' is set appropriately.

!!ERRORS

Depending on the file system, other errors can be returned.
The more general errors for __chmod__ are listed
below:
;[EPERM]: The effective UID does not match the owner of the file, and is not zero.
;[EROFS]: The named file resides on a read-only file system.
;[EFAULT]: ''path'' points outside your accessible address space.
;[ENAMETOOLONG]: ''path'' is too long.
;[ENOENT]: The file does not exist.
;[ENOMEM]: Insufficient kernel memory was available.
;[ENOTDIR]: A component of the path prefix is not a directory.
;[EACCES]: Search permission is denied on a component of the path prefix.
;[ELOOP]: Too many symbolic links were encountered in resolving ''path''.
;[EIO]: An I/O error occurred.

!!CONFORMING TO

The __chmod__ call conforms to SVr4, SVID, POSIX, X/OPEN, 4.4BSD. SVr4 documents EINTR, ENOLINK and EMULTIHOP returns, but no ENOMEM. POSIX.1 does not document EFAULT, ENOMEM, ELOOP or EIO error conditions, or the macros __S_IREAD__, __S_IWRITE__ and __S_IEXEC__.

POSIX and X/OPEN do not document the sticky bit.
!!SEE ALSO

open(2), chown(2), execve(2), stat(2)

13 pages link to chmod(2):

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Last edited on Tuesday, October 29, 2002 11:49:53 pm by PerryLorier

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