CHMOD (2)
change permissions of a file
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
int chmod(const char * path , mode_t mode );
int fchmod(int fildes , mode_t mode );
DESCRIPTION
The mode of the file given by
path
or referenced by
fildes
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
S_IRUSR (S_IREAD)
S_IWUSR (S_IWRITE)
S_IXUSR (S_IEXEC)
00100 execute/search by owner
S_IRGRP
S_IWGRP
S_IXGRP
00010 execute/search by group
S_IROTH
S_IWOTH
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 (e.g.,
for directories, a file can only be deleted by the owner or the super-user).
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
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.
The
fchmod
call conforms to 4.4BSD and SVr4.
SVr4 documents additional EINTR and ENOLINK error conditions.
POSIX requires the
fchmod
function if at least one of
_POSIX_MAPPED_FILES
and
_POSIX_SHARED_MEMORY_OBJECTS
is defined, and documents additional ENOSYS and EINVAL error
conditions, but does not document EIO.
POSIX and X/OPEN do not document the sticky bit.
SEE ALSO
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