WRITE(S)                 XENIX System V                  WRITE(S)



     Name
          write - Writes to a file.

     Syntax
          int write (fildes, buf, nbyte)
          int fildes;
          char *buf;
          unsigned nbyte;

     Description
          fildes is a file descriptor obtained from a creat, open,
          dup, fcntl, or pipe system call.

          write attempts to write nbyte bytes from the buffer pointed
          to by buf to the file associated with the fildes.

          On devices capable of seeking, the actual writing of data
          proceeds from the position in the file indicated by the file
          pointer.  Upon return from write, the file pointer is
          incremented by the number of bytes actually written.

          On devices incapable of seeking, writing always takes place
          starting at the current position.  The value of a file
          pointer associated with such a device is undefined.

          If the O_APPEND flag of the file status flags is set, the
          file pointer is set to the end of the file prior to each
          write.

          write will fail and the file pointer will remain unchanged
          if one or more of the following are true:

               fildes is not a valid file descriptor open for writing.
               [EBADF]

               An attempt is made to write to a pipe that is not open
               for reading by any process.  [EPIPE and SIGPIPE signal]

               An attempt was made to write a file that exceeds the
               process' file size limit or the maximum file size.  See
               ulimit(S).  [EFBIG]

               buf points outside the process' allocated address
               space.  [EFAULT]

               A signal was caught during the write system call.
               [EINTR]

               There is no free space remaining on the device
               containing the file.

          If a write requests that more bytes be written than there is



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     WRITE(S)                 XENIX System V                  WRITE(S)



          room for (e.g., the ulimit (see ulimit(S)) or the physical
          end of a medium), only as many bytes as there is room for
          will be written.  For example, suppose there is space for 20
          bytes more in a file before reaching a limit.  A write of
          512  bytes will return 20.  The next write of a nonzero
          number of bytes gives a failure return (except as noted
          below).

          If the file being written is a pipe (or FIFO), no partial
          writes are permitted.  Thus, the write will fail if a write
          of nbyte bytes exceeds a limit.

          If the file being written is a pipe (or FIFO) and the
          O_NDELAY flag of the file flag word is set, then a write to
          a full pipe (or FIFO) returns a count of 0.  Otherwise
          (O_NDELAY clear), writes to a full pipe (or FIFO) block
          until space becomes available.

     Return Value
          Upon successful completion, the number of bytes actually
          written is returned.  Otherwise, -1 is returned and errno is
          set to indicate the error.

     See Also
          creat(S), dup(S), lseek(S), open(S), pipe(S), ulimit(S)

     Notes
          Writing a region of a file locked with locking causes write
          to hang indefinitely until the locked region is unlocked.


























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