write - write output
ssize_t write(int d, const void *buf, size_t nbytes)
Write attempts to write nbytes of data to the object referenced by the
descriptor d from the buffer pointed to by buf.
On objects capable of seeking, the write starts at a position given by
the pointer associated with d, see lseek(2). Upon return from write, the
pointer is incremented by the number of bytes actually written.
Objects that are not capable of seeking always write from the current
position. The value of the pointer associated with such an object is
When using non-blocking I/O on objects such as TCP/IP channels that are
subject to flow control, write may write fewer bytes than requested; the
return value must be noted, and the remainder of the operation should be
retried when possible.
Upon successful completion the number of bytes actually written is
returned. Otherwise a -1 is returned and the global variable errno is
set to indicate the error.
Write will fail and the file pointer will remain unchanged if one or more
of the following are true:
[EBADF] D is not a valid descriptor open for writing.
[EPIPE] An attempt is made to write to a pipe that is not open for
reading by any process.
[EPIPE] An attempt is made to write to a TCP channel that is not
connected to a peer socket.
[EFBIG] An attempt was made to write a file that exceeds the
process's file size limit or the maximum file size.
[EFAULT] Part of the data to be written to the file points outside
the process's allocated address space.
[ENOSPC] There is no free space remaining on the file system
containing the file.
[EIO] An I/O error occurred while reading from or writing to the
[EAGAIN] The file was marked for non-blocking I/O, and no data
could be written immediately.
fcntl(2), lseek(2), open(2), pipe(2), read(2).