write writes up to count bytes to the file referenced by the file
descriptor fd from the buffer starting at buf. POSIX requires
that a read() which can be proved to occur after a write() has
returned returns the new data. Note that not all file systems are POSIX
On success, the number of bytes written are returned (zero indicates nothing was
written). On error, -1 is returned, and errno is set appropriately. If
count is zero and the file descriptor refers to a regular file, 0 will
be returned without causing any other effect. For a special file, the results
are not portable.
Non-blocking I/O has been selected using O_NONBLOCK
and the write would block.
fd is not a valid file descriptor or is not open for
buf is outside your accessible address space.
An attempt was made to write a file that exceeds the
implementation-defined maximum file size or the process' file size limit,
or to write at a position past than the maximum allowed offset.
The call was interrupted by a signal before any data was
fd is attached to an object which is unsuitable for
A low-level I/O error occurred while modifying the
The device containing the file referred to by fd has
no room for the data.
fd is connected to a pipe or socket whose reading
end is closed. When this happens the writing process will also receive a
SIGPIPE signal. (Thus, the write return value is seen only if the
program catches, blocks or ignores this signal.)
Other errors may occur, depending on the object connected to fd.
SVr4, SVID, POSIX, X/OPEN, 4.3BSD. SVr4 documents additional error conditions
EDEADLK, ENOLCK, ENOLNK, ENOSR, ENXIO, or ERANGE. Under SVr4 a write may be
interrupted and return EINTR at any point, not just before any data is
A successful return from write does not make any guarantee that data has
been committed to disk. In fact, on some buggy implementations, it does not
even guarantee that space has successfully been reserved for the data. The
only way to be sure is to call fsync(2) after you are done writing all