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

.TH CREAT 2 "2 July 1983"
.UC 4
.SH NAME
creat \- create a new file
.SH SYNOPSIS
.nf
.B creat(name, mode)
.B char *name;
.fi
.SH DESCRIPTION
.B "This interface is obsoleted by open(2).
.PP
.I Creat
creates a new file or prepares to rewrite an existing
file called 
.IR name ,
given as the address of a null-terminated string.
If the file did not exist, it is given
mode
.IR mode ,
as modified by the process's mode mask (see
.IR umask (2)).
Also see
.IR  chmod (2)
for the
construction of the
.I mode
argument.
.PP
If the file did exist, its mode and owner remain unchanged
but it is truncated to 0 length.
.PP
The file is also opened for writing, and its file descriptor
is returned.
.SH NOTES
The
.I mode
given is arbitrary; it need not allow
writing.
This feature has been used in the past by
programs to construct a simple exclusive locking
mechanism.  It is replaced by the O_EXCL open
mode, or 
.IR flock (2)
facilitity.
.SH "RETURN VALUE
The value \-1 is returned if an error occurs.  Otherwise,
the call returns a non-negative descriptor which only permits
writing.
.SH ERRORS
.I Creat
will fail and the file will not be created or truncated
if one of the following occur:
.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
[EACCES]
A needed directory does not have search permission.
.TP 15
[EACCES]
The file does not exist and the directory
in which it is to be created is not writable.
.TP 15
[EACCES]
The file exists, but it is unwritable.
.TP 15
[EISDIR]
The file is a directory.
.TP 15
[EMFILE]
There are already too many files open.
.TP 15
[EROFS]
The named file resides on a read-only file system.
.TP 15
[ENXIO]
The file is a character special or block special file, and
the associated device does not exist.
.TP 15
[ETXTBSY]
The file is a pure procedure (shared text) file that is being
executed.
.TP 15
[EFAULT]
.I Name
points outside the process's allocated address space.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating the
pathname.
.TP 15
[EOPNOTSUPP]
The file was a socket (not currently implemented).
.SH "SEE ALSO"
open(2), write(2), close(2), chmod(2), umask(2)