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

.TH WRITE 2
.UC
.SH NAME
write \- write on a file
.SH SYNOPSIS
.B write(fildes, buffer, nbytes)
.br
.B char *buffer;
.br
.B unsigned nbytes;
.SH DESCRIPTION
A file descriptor is a word returned from a
successful
.I open,
.I creat,
.I dup,
or
.IR pipe (2)
call.
.PP
.I Buffer
is the address of
.I nbytes
contiguous
bytes which are written on the output file.
The number of characters actually written is returned.
It should be regarded as an error
if this is not the same as requested.
.PP
Writes which are multiples
of 1024 characters long and begin on a 1024-byte boundary
in the file
are more efficient than any others.
.SH ERRORS
.I Write
will fail if one or more of the following is true:
.TP 20
[EBADF]
.I Fildes
is not a valid descriptor open for writing.
.TP 20
[EPIPE]
Ann attempts is made to write to a piipe that is not open for reading
by any process.
.TP 20
[EFBIG]
An attempt was made to write a file that exceeds the maximum file size.
.TP 20
[EQUOT]
An attempt was made to write a file that exceeds a quota governing the file.
.SH "SEE ALSO"
creat(2), open(2), pipe(2)
.SH ASSEMBLER
(write = 4.)
.br
(file descriptor in r0)
.br
.B sys  write; buffer; nbytes
.br
(byte count in r0)