4.2BSD/usr/man/man2/chmod.2

.TH CHMOD 2 "2 July 1983"
.UC 4
.SH NAME
chmod \- change mode of file
.SH SYNOPSIS
.nf
.ft B
chmod(path, mode)
char *path;
int mode;
.PP
.ft B
fchmod(fd, mode)
int fd, mode;
.fi
.SH DESCRIPTION
The file whose name
is given by \fIpath\fP
or referenced by the descriptor
.I fd
has its mode changed to
.IR mode .
Modes are constructed by
.IR or 'ing
together some
combination of the following:
.PP
.RS
 04000 set user ID on execution
 02000 set group ID on execution
 01000 save text image after execution
 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
.RE
.PP
If an executable file is set up for sharing (this is the default)
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.
.PP
Only the owner of a file (or the super-user) may change the mode.
.PP
Writing or changing the owner of a file
turns off the set-user-id and set-group-id bits.
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.
.SH "RETURN VALUE
Upon successful completion, a value of 0 is returned.
Otherwise, a value of \-1 is returned and
.I errno
is set to indicate the error.
.SH "ERRORS
.I Chmod
will fail and the file mode will be unchanged if:
.TP 15
[EPERM]
The argument contains a byte with the high-order bit set.
.TP 15
[ENOTDIR]
A component of the path prefix is not a directory.
.TP 15
[ENOENT]
The pathname was too long.
.TP 15
[ENOENT]
The named file does not exist.
.TP 15
[EACCES]
Search permission is denied on a component of the path prefix.
.TP 15
[EPERM]
The effective user ID does not match the owner of the file and
the effective user ID is not the super-user.
.TP 15
[EROFS]
The named file resides on a read-only file system.
.TP 15
[EFAULT]
.I Path
points outside the process's allocated address space.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating the pathname.
.PP
.I Fchmod
will fail if:
.TP 15
[EBADF]
The descriptor is not valid.
.TP 15
[EINVAL]
.I Fd
refers to a socket, not to a file.
.TP 15
[EROFS]
The file resides on a read-only file system.
.SH "SEE ALSO"
open(2), chown(2)