NAME

SYNOPSIS

       #include <unistd.h>

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

DESCRIPTION

       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  con-
       forming.

RETURN VALUE

       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.

ERRORS

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

       EEINVAL fd is attached to an object which is unsuitable for writing.

       EFAULT  buf is outside your accessible address space.

       EFBIG   An attempt was made to write a file that exceeds the implementa-
              tion-defined maximum file size or the process’ file size  limit,
              or  to write at a position past than the maximum allowed offset.

       EPIPE  fd is connected to a pipe or socket whose reading end is closed.
              When  this  happens the writing process will also receive a SIG-
              PIPE signal.  (Thus, the write return value is seen only if  the
              program catches, blocks or ignores this signal.)

       EAGAIN Non-blocking  I/O  has  been  selected  using O_NONBLOCK and the
              write would block.

       EINTR  The call was interrupted by a signal before any data  was  writ-
              ten.

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

       EEIIOO    A low-level I/O error occurred while modifying the inode.

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

CONFORMING TO

       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 written.

NOTES

       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 your data.

SEE ALSO

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

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©2004, Gary L. Burt