1WRITE(2) 386BSD Programmer's Manual WRITE(2) 2 3NNAAMMEE 4 wwrriittee, wwrriitteevv - write output 5 6SSYYNNOOPPSSIISS 7 ##iinncclluuddee <<uunniissttdd..hh>> 8 ##iinncclluuddee <<ssyyss//ttyyppeess..hh>> 9 ##iinncclluuddee <<ssyyss//uuiioo..hh>> 10 11 _s_s_i_z_e__t 12 wwrriittee(_i_n_t _d, _c_o_n_s_t _c_h_a_r *_b_u_f, _s_i_z_e__t _n_b_y_t_e_s) 13 14 _i_n_t 15 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) 16 17DDEESSCCRRIIPPTTIIOONN 18 WWrriittee() attempts to write _n_b_y_t_e_s of data to the object referenced by the 19 descriptor _d from the buffer pointed to by _b_u_f. WWrriitteevv() performs the 20 same action, but gathers the output data from the _i_o_v_c_n_t buffers 21 specified by the members of the _i_o_v array: iov[0], iov[1], ..., 22 iov[iovcnt-1]. 23 24 For wwrriitteevv(), the _i_o_v_e_c structure is defined as: 25 struct iovec { 26 caddr_t iov_base; 27 int iov_len; 28 }; 29 30 Each _i_o_v_e_c entry specifies the base address and length of an area in 31 memory from which data should be written. WWrriitteevv() will always write a 32 complete area before proceeding to the next. 33 34 On objects capable of seeking, the wwrriittee() starts at a position given by 35 the pointer associated with _d, see lseek(2). Upon return from wwrriittee(), 36 the pointer is incremented by the number of bytes which were written. 37 38 Objects that are not capable of seeking always write from the current 39 position. The value of the pointer associated with such an object is 40 undefined. 41 42 If the real user is not the super-user, then wwrriittee() clears the set-user- 43 id bit on a file. This prevents penetration of system security by a user 44 who ``captures'' a writable set-user-id file owned by the super-user. 45 46 When using non-blocking I/O on objects such as sockets that are subject 47 to flow control, wwrriittee() and wwrriitteevv() may write fewer bytes than 48 requested; the return value must be noted, and the remainder of the 49 operation should be retried when possible. 50 51RREETTUURRNN VVAALLUUEESS 52 Upon successful completion the number of bytes which were written is 53 returned. Otherwise a -1 is returned and the global variable _e_r_r_n_o is 54 set to indicate the error. 55 56EERRRROORRSS 57 WWrriittee() and wwrriitteevv() will fail and the file pointer will remain unchanged 58 if: 59 60 [EBADF] _D is not a valid descriptor open for writing. 61 62 [EPIPE] An attempt is made to write to a pipe that is not open for 63 reading by any process. 64 65 [EPIPE] An attempt is made to write to a socket of type that is not 66 67 connected to a peer socket. 68 69 [EFBIG] An attempt was made to write a file that exceeds the 70 process's file size limit or the maximum file size. 71 72 [EFAULT] Part of _i_o_v or data to be written to the file points 73 outside the process's allocated address space. 74 75 [EINVAL] The pointer associated with _d was negative. 76 77 [ENOSPC] There is no free space remaining on the file system 78 containing the file. 79 80 [EDQUOT] The user's quota of disk blocks on the file system 81 containing the file has been exhausted. 82 83 [EIO] An I/O error occurred while reading from or writing to the 84 file system. 85 86 [EWOULDBLOCK] 87 The file was marked for non-blocking I/O, and no data could 88 be written immediately. 89 90 In addition, wwrriitteevv() may return one of the following errors: 91 92 [EINVAL] _I_o_v_c_n_t was less than or equal to 0, or greater than 16. 93 94 [EINVAL] One of the _i_o_v__l_e_n values in the _i_o_v array was negative. 95 96 [EINVAL] The sum of the _i_o_v__l_e_n values in the _i_o_v array overflowed a 97 32-bit integer. 98 99SSEEEE AALLSSOO 100 fcntl(2), lseek(2), open(2), pipe(2), select(2) 101 102SSTTAANNDDAARRDDSS 103 WWrriittee() is expected to conform to IEEE Std 1003.1-1988 (``POSIX''). 104 105HHIISSTTOORRYY 106 The wwrriitteevv() function call appeared in 4.2BSD. A wwrriittee function call 107 appeared in Version 6 AT&T UNIX. 108 1094th Berkeley Distribution March 10, 1991 2 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133