|CHMOD(2)||System Calls Manual||CHMOD(2)|
fchmod — change mode of
char *path, mode_t
fd, const char
*path, mode_t mode,
chmod() function sets the file
permission bits of the file specified by the pathname
path to mode.
chmod() verifies that the process owner (user)
either owns the specified file or is the superuser.
The mode argument is the bitwise OR of zero or more of the permission bit masks from the following list:
#define S_IRWXU 0000700 /* RWX mask for owner */ #define S_IRUSR 0000400 /* R for owner */ #define S_IWUSR 0000200 /* W for owner */ #define S_IXUSR 0000100 /* X for owner */ #define S_IRWXG 0000070 /* RWX mask for group */ #define S_IRGRP 0000040 /* R for group */ #define S_IWGRP 0000020 /* W for group */ #define S_IXGRP 0000010 /* X for group */ #define S_IRWXO 0000007 /* RWX mask for other */ #define S_IROTH 0000004 /* R for other */ #define S_IWOTH 0000002 /* W for other */ #define S_IXOTH 0000001 /* X for other */ #define S_ISUID 0004000 /* set user id on execution */ #define S_ISGID 0002000 /* set group id on execution */ #define S_ISVTX 0001000 /* save swapped text even after use */
ISVTX (the sticky
bit) is set on a file, it is ignored.
ISVTX (the sticky
bit) is set on a directory, an unprivileged user may not delete or
rename files of other users in that directory. The sticky bit may be set by
any user on a directory which the user owns or has appropriate permissions.
For more details of the properties of the sticky bit, see
Writing or changing the owner of a file turns off the set-user-ID and set-group-ID bits unless the user is the superuser. This makes the system somewhat more secure by protecting set-user-ID (set-group-ID) files from remaining set-user-ID (set-group-ID) if they are modified, at the expense of a degree of compatibility.
fchmodat() function is equivalent to
chmod() except in the case where
path specifies a relative path. In this case the file
to be changed is determined relative to the directory associated with the
file descriptor fd instead of the current working
fchmodat() is passed the special value
AT_FDCWD (defined in
<fcntl.h>) in the
fd parameter, the current working directory is used.
If flag is also zero, the behavior is identical to a
The flag argument is the bitwise OR of zero or more of the following values:
fchmod() function is equivalent to
chmod() except that the file whose permissions are
changed is specified by the file descriptor fd.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
fchmodat() functions will fail and the file mode
will be unchanged if:
NAME_MAXcharacters, or an entire pathname (including the terminating NUL) exceeded
fchmodat() function will
AT_FDCWDnor a valid file descriptor.
AT_SYMLINK_NOFOLLOWon a symbolic link and the file system does not support that operation.
fchmod() will fail and the file mode will
be unchanged if:
functions are expected to conform to IEEE Std 1003.1-2008
chmod() system call first appeared in
Version 1 AT&T UNIX;
fchmod() in 4.1cBSD; and
fchmodat() has been available since
|September 10, 2015||OpenBSD-6.2|