write - write output

     #include <sys/types.h>
     #include <unistd.h>

     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
                    file system.

     [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).