write - write to a file descriptor


       #include <unistd.h>

       ssize_t write(int fd, const void *buf, size_t count);


       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 conforming.


       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.


       EBADF  fd is not a valid file descriptor or  is  not  open
              for writing.

       EINVAL fd is attached to an object which is unsuitable for

       EFAULT buf is outside your accessible address space.

       EPIPE  fd is connected to a pipe or socket  whose  reading
              end  is closed.  When this happens the writing pro­
              cess will receive a SIGPIPE signal; if it  catches,
              blocks or ignores this the error EPIPE is returned.

       EAGAIN Non-blocking I/O has been selected using O_NONBLOCK
              and  there  was  no room in the pipe or socket con­
              nected to fd to write the data immediately.

       EINTR  The call was interrupted by  a  signal  before  any
              data was written.

       ENOSPC The  device  containing  the file referred to by fd
              has no room for the data.

       EIO    A low-level I/O error occurred while modifying  the

       Other  errors may occur, depending on the object connected
       to fd.

       SVr4, SVID, POSIX, X/OPEN, 4.3BSD.  SVr4  documents  addi­
       tional  error  conditions  EDEADLK, EFBIG, ENOLCK, ENOLNK,
       ENOSR, ENXIO, EPIPE, or ERANGE.  Under SVr4 a write may be
       interrupted and return EINTR at any point, not just before
       any data is written.


       open(2), read(2), fcntl(2), close(2), lseek(2), select(2),
       ioctl(2), fsync(2), fwrite(3)