4.4BSD/usr/share/man/cat2/writev.0

WRITE(2)                    BSD Programmer's Manual                   WRITE(2)

NNAAMMEE
     wwrriittee, wwrriitteevv - write output

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<uunniissttdd..hh>>
     ##iinncclluuddee <<ssyyss//ttyyppeess..hh>>
     ##iinncclluuddee <<ssyyss//uuiioo..hh>>

     _s_s_i_z_e___t
     wwrriittee(_i_n_t _d, _c_o_n_s_t _v_o_i_d _*_b_u_f, _s_i_z_e___t _n_b_y_t_e_s);

     _i_n_t
     wwrriitteevv(_i_n_t _d, _s_t_r_u_c_t _i_o_v_e_c _*_i_o_v, _i_n_t _i_o_v_c_n_t);

DDEESSCCRRIIPPTTIIOONN
     WWrriittee() attempts to write _n_b_y_t_e_s of data to the object referenced by the
     descriptor _d from the buffer pointed to by _b_u_f. WWrriitteevv() performs the
     same action, but gathers the output data from the _i_o_v_c_n_t buffers speci-
     fied by the members of the _i_o_v array: iov[0], iov[1], ..., iov[iovcnt-1].

     For wwrriitteevv(), the _i_o_v_e_c structure is defined as:
           struct iovec {
                   void *iov_base;
                   int iov_len;
           };

     Each _i_o_v_e_c entry specifies the base address and length of an area in mem-
     ory from which data should be written.  WWrriitteevv() will always write a com-
     plete area before proceeding to the next.

     On objects capable of seeking, the wwrriittee() starts at a position given by
     the pointer associated with _d, see lseek(2).  Upon return from wwrriittee(),
     the pointer is incremented by the number of bytes which were written.

     Objects that are not capable of seeking always write from the current po-
     sition.  The value of the pointer associated with such an object is unde-
     fined.

     If the real user is not the super-user, then wwrriittee() clears the set-user-
     id bit on a file.  This prevents penetration of system security by a user
     who ``captures'' a writable set-user-id file owned by the super-user.

     When using non-blocking I/O on objects such as sockets that are subject
     to flow control, wwrriittee() and wwrriitteevv() may write fewer bytes than request-
     ed; the return value must be noted, and the remainder of the operation
     should be retried when possible.

RREETTUURRNN VVAALLUUEESS
     Upon successful completion the number of bytes which were written is re-
     turned.  Otherwise a -1 is returned and the global variable _e_r_r_n_o is set
     to indicate the error.

EERRRROORRSS
     WWrriittee() and wwrriitteevv() will fail and the file pointer will remain unchanged
     if:

     [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 socket of type that is not

                   connected to a peer socket.

     [EFBIG]       An attempt was made to write a file that exceeds the pro-
                   cess's file size limit or the maximum file size.

     [EFAULT]      Part of _i_o_v or data to be written to the file points out-
                   side the process's allocated address space.

     [EINVAL]      The pointer associated with _d was negative.

     [ENOSPC]      There is no free space remaining on the file system con-
                   taining the file.

     [EDQUOT]      The user's quota of disk blocks on the file system contain-
                   ing the file has been exhausted.

     [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.

     In addition, wwrriitteevv() may return one of the following errors:

     [EINVAL]      _I_o_v_c_n_t was less than or equal to 0, or greater than 16.

     [EINVAL]      One of the _i_o_v___l_e_n values in the _i_o_v array was negative.

     [EINVAL]      The sum of the _i_o_v___l_e_n values in the _i_o_v array overflowed a
                   32-bit integer.

SSEEEE AALLSSOO
     fcntl(2),  lseek(2),  open(2),  pipe(2),  select(2)

SSTTAANNDDAARRDDSS
     WWrriittee() is expected to conform to IEEE Std 1003.1-1988 (``POSIX'').

HHIISSTTOORRYY
     The wwrriitteevv() function call appeared in 4.2BSD. A wwrriittee function call ap-
     peared in Version 6 AT&T UNIX.

4th Berkeley Distribution        June 4, 1993                                2