2.9BSD/usr/man/man2/chmod.2

.TH CHMOD 2 
.UC
.SH NAME
chmod \- change mode of file
.SH SYNOPSIS
.B chmod(name, mode)
.br
.B char *name;
.SH DESCRIPTION
The file whose name
is given as the null-terminated string pointed to by
.I name
has its mode changed to
.IR mode .
Modes are constructed by ORing 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
(\fB\-n\fP or \fB\-i\fP option of
.IR ld (1))
then mode 01000 prevents the system from
abandoning the swap-space image of the program-text portion
of the file when its last user
terminates.
Thus when the next user of the file executes it,
the text need not be read from the file
system but can simply be swapped in,
saving time.
Ability to set this bit is restricted to the super-user
since swap space is consumed
by the images; it is only worth while for heavily used commands.
.PP
If a directory (for example, /tmp) has the 01000 bit on in its mode,
only the user himself (or the super-user) may delete files he owns
from the directory (regardless of other ``write'' permissions).
.PP
Only the owner of a file (or the super-user) may change the mode.
Only the super-user can set the 01000 mode.
.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 20
[EINVAL]
The path name contained a non-ASCII byte.
.TP 20
[ENOTDIR]
A component of the path prefix is not a directory.
.TP 20
[ENOENT]
The named file does not exist.
.TP 20
[EACCES]
Search permission is denied on a component of the path prefix.
.TP 20
[EPERM]
The effective user ID does not match the owner of the file and the
effective user ID is not the super-user.
.TP 20
[EROFS]
The named file resdes on a read-only file system.
.TP 20
[EFAULT]
.I Name
points outside the process's allocated address space.
.TP 20
[ELOOP]
Too many symbolic links were encountered in translating the path name.
.SH "SEE ALSO"
chmod(1)
.SH ASSEMBLER
(chmod = 15.)
.br
.B sys chmod; name; mode