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Annotation of 43BSDTahoe/man/man2/write.2, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1980 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)write.2     6.5 (Berkeley) 5/14/86
        !             6: .\"
        !             7: .TH WRITE 2 "May 14, 1986"
        !             8: .UC 4
        !             9: .SH NAME
        !            10: write, writev \- write output
        !            11: .SH SYNOPSIS
        !            12: .nf
        !            13: .ft B
        !            14: cc = write(d, buf, nbytes)
        !            15: int cc, d;
        !            16: char *buf;
        !            17: int nbytes;
        !            18: .PP
        !            19: .ft B
        !            20: #include <sys/types.h>
        !            21: #include <sys/uio.h>
        !            22: .PP
        !            23: .ft B
        !            24: cc = writev(d, iov, iovcnt)
        !            25: int cc, d;
        !            26: struct iovec *iov;
        !            27: int iovcnt;
        !            28: .fi
        !            29: .SH DESCRIPTION
        !            30: .I Write
        !            31: attempts to write
        !            32: .I nbytes
        !            33: of data to the object referenced by the descriptor
        !            34: .I d
        !            35: from the buffer pointed to by
        !            36: .IR buf .
        !            37: .I Writev
        !            38: performs the same action, but gathers the output data
        !            39: from the 
        !            40: .I iovcnt
        !            41: buffers specified by the members of the
        !            42: .I iov
        !            43: array: iov[0], iov[1], ..., iov[iovcnt\|\-\|1].
        !            44: .PP
        !            45: For 
        !            46: .IR writev ,
        !            47: the 
        !            48: .I iovec
        !            49: structure is defined as
        !            50: .PP
        !            51: .nf
        !            52: .RS
        !            53: .DT
        !            54: struct iovec {
        !            55:        caddr_t iov_base;
        !            56:        int     iov_len;
        !            57: };
        !            58: .RE
        !            59: .fi
        !            60: .PP
        !            61: Each 
        !            62: .I iovec
        !            63: entry specifies the base address and length of an area
        !            64: in memory from which data should be written.
        !            65: .I Writev
        !            66: will always write a complete area before proceeding
        !            67: to the next.
        !            68: .PP
        !            69: On objects capable of seeking, the \fIwrite\fP starts at a position
        !            70: given by the pointer associated with
        !            71: .IR d ,
        !            72: see
        !            73: .IR lseek (2).
        !            74: Upon return from
        !            75: .IR write ,
        !            76: the pointer is incremented by the number of bytes actually written.
        !            77: .PP
        !            78: Objects that are not capable of seeking always write from the current
        !            79: position.  The value of the pointer associated with such an object
        !            80: is undefined.
        !            81: .PP
        !            82: If the real user is not the super-user, then
        !            83: .I write
        !            84: clears the set-user-id bit on a file.
        !            85: This prevents penetration of system security
        !            86: by a user who
        !            87: \*(lqcaptures\*(rq a writable set-user-id file
        !            88: owned by the super-user.
        !            89: .PP
        !            90: When using non-blocking I/O on objects such as sockets that are subject
        !            91: to flow control,
        !            92: .I write
        !            93: and
        !            94: .I writev
        !            95: may write fewer bytes than requested;
        !            96: the return value must be noted,
        !            97: and the remainder of the operation should be retried when possible.
        !            98: .SH "RETURN VALUE
        !            99: Upon successful completion the number of bytes actually written
        !           100: is returned.  Otherwise a \-1 is returned and the global variable
        !           101: .I errno
        !           102: is set to indicate the error.
        !           103: .SH ERRORS
        !           104: .I Write
        !           105: and
        !           106: .I writev
        !           107: will fail and the file pointer will remain unchanged if one or more
        !           108: of the following are true:
        !           109: .TP 15
        !           110: [EBADF]
        !           111: \fID\fP is not a valid descriptor open for writing.
        !           112: .TP 15
        !           113: [EPIPE]
        !           114: An attempt is made to write to a pipe that is not open
        !           115: for reading by any process.
        !           116: .TP 15
        !           117: [EPIPE]
        !           118: An attempt is made to write to a socket of type SOCK_STREAM
        !           119: that is not connected to a peer socket.
        !           120: .TP 15
        !           121: [EFBIG]
        !           122: An attempt was made to write a file that exceeds the process's
        !           123: file size limit or the maximum file size.
        !           124: .TP 15
        !           125: [EFAULT]
        !           126: Part of \fIiov\fP or data to be written to the file
        !           127: points outside the process's allocated address space.
        !           128: .TP 15
        !           129: [EINVAL]
        !           130: The pointer associated with
        !           131: .I d
        !           132: was negative.
        !           133: .TP 15
        !           134: [ENOSPC]
        !           135: There is no free space remaining on the file system
        !           136: containing the file.
        !           137: .TP 15
        !           138: [EDQUOT]
        !           139: The user's quota of disk blocks on the file system
        !           140: containing the file has been exhausted.
        !           141: .TP 15
        !           142: [EIO]
        !           143: An I/O error occurred while reading from or writing to the file system.
        !           144: .TP 15
        !           145: [EWOULDBLOCK]
        !           146: The file was marked for non-blocking I/O,
        !           147: and no data could be written immediately.
        !           148: .PP
        !           149: In addition, 
        !           150: .I writev
        !           151: may return one of the following errors:
        !           152: .TP 15
        !           153: [EINVAL]
        !           154: .I Iovcnt
        !           155: was less than or equal to 0, or greater than 16.
        !           156: .TP 15
        !           157: [EINVAL]
        !           158: One of the
        !           159: .I iov_len
        !           160: values in the
        !           161: .I iov
        !           162: array was negative.
        !           163: .TP 15
        !           164: [EINVAL]
        !           165: The sum of the
        !           166: .I iov_len
        !           167: values in the
        !           168: .I iov
        !           169: array overflowed a 32-bit integer.
        !           170: .SH "SEE ALSO"
        !           171: fcntl(2), lseek(2), open(2), pipe(2), select(2)

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