CHMOD(2)CHMOD(2)NAME
chmod, fchmod - change mode of file
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
int chmod(const char *path, mode_t mode)
DESCRIPTION
The file whose name is given by path has its mode changed to mode.
Modes are constructed by or'ing together some combination of the fol‐
lowing, defined in <sys/stat.h>:
S_ISUID 04000 set user ID on execution
S_ISGID 02000 set group ID on execution
S_ISVTX 01000 `sticky bit' (see below)
S_IRWXU 00700 read, write, execute by owner
S_IRUSR 00400 read by owner
S_IWUSR 00200 write by owner
S_IXUSR 00100 execute (search on directory) by owner
S_IRWXG 00070 read, write, execute by group
S_IRGRP 00040 read by group
S_IWGRP 00020 write by group
S_IXGRP 00010 execute (search on directory) by group
S_IRWXO 00007 read, write, execute by others
S_IROTH 00004 read by others
S_IWOTH 00002 write by others
S_IXOTH 00001 execute (search on directory) by others
If mode ISVTX (the `sticky bit') is set on a directory, an unprivileged
user may not delete or rename files of other users in that directory.
(Minix-vmd)
Only the owner of a file (or the super-user) may change the mode.
Writing or changing the owner of a file turns off the set-user-id and
set-group-id bits unless the user is the super-user. 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.
RETURN VALUE
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and errno is set to indicate the error.
ERRORS
Chmod will fail and the file mode will be unchanged if:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] The path name exceeds PATH_MAX characters.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the path
prefix.
[ELOOP] Too many symbolic links were encountered in translating
the pathname. (Minix-vmd)
[EPERM] The effective user ID does not match the owner of the
file and the effective user ID is not the super-user.
[EROFS] The named file resides on a read-only file system.
[EFAULT] Path points outside the process's allocated address
space.
[EIO] An I/O error occurred while reading from or writing to
the file system.
SEE ALSOchmod(1), open(2), chown(2), stat(2).
NOTES
The sticky bit was historically used to lock important executables into
memory.
4th Berkeley Distribution May 13, 1986 CHMOD(2)
