Chip 1995 March/CHIP3.mdf/slackwar/a/util/util-lin.10/util-lin/util-linux-1.10/ttymsg.c

C/C++ Source or Header | 1993-03-08 | 4.9 KB | 174 lines

/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Modified for Linux (which doesn\'t have snprintf()) by [e-mail]
 * on Sun Mar  7 16:14:18 1993.
 *
 */

#ifndef lint
static char sccsid[] = "@(#)ttymsg.c    5.8 (Berkeley) 7/1/91";
#endif /* not lint */

#include <sys/types.h>
#include <sys/uio.h>
#include <signal.h>
#include <fcntl.h>
#include <dirent.h>
#include <errno.h>
#include <paths.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

/*
 * Display the contents of a uio structure on a terminal.  Used by wall(1)
 * and syslogd(8).  Forks and finishes in child if write would block, waiting
 * at most five minutes.  Returns pointer to error string on unexpected error;
 * string is not newline-terminated.  Various "normal" errors are ignored
 * (exclusive-use, lack of permission, etc.).
 */
char *
ttymsg(iov, iovcnt, line)
    struct iovec *iov;
    int iovcnt;
    char *line;
{
    static char device[MAXNAMLEN] = _PATH_DEV;
    static char errbuf[1024];
    register int cnt, fd, left, wret;
    struct iovec localiov[6];
    int forked = 0;

    if (iovcnt > 6)
        return ("too many iov's (change code in wall/ttymsg.c)");
    /*
     * open will fail on slip lines or exclusive-use lines
     * if not running as root; not an error.
     */
    (void) strcpy(device + sizeof(_PATH_DEV) - 1, line);
    if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
        if (errno == EBUSY || errno == EACCES)
            return (NULL);
#ifdef __linux__
        (void) sprintf(errbuf,
            "%s: %s", device, strerror(errno));
#else
        (void) snprintf(errbuf, sizeof(errbuf),
            "%s: %s", device, strerror(errno));
#endif
        return (errbuf);
    }

    for (cnt = left = 0; cnt < iovcnt; ++cnt)
        left += iov[cnt].iov_len;

    for (;;) {
        wret = writev(fd, iov, iovcnt);
        if (wret >= left)
            break;
        if (wret >= 0) {
            left -= wret;
            if (iov != localiov) {
                bcopy(iov, localiov,
                    iovcnt * sizeof(struct iovec));
                iov = localiov;
            }
            for (cnt = 0; wret >= iov->iov_len; ++cnt) {
                wret -= iov->iov_len;
                ++iov;
                --iovcnt;
            }
            if (wret) {
                iov->iov_base += wret;
                iov->iov_len -= wret;
            }
            continue;
        }
        if (errno == EWOULDBLOCK) {
            int cpid, off = 0;

            if (forked) {
                (void) close(fd);
                _exit(1);
            }
            cpid = fork();
            if (cpid < 0) {
#ifdef __linux__
                (void) sprintf(errbuf,
                    "fork: %s", strerror(errno));
#else
                (void) snprintf(errbuf, sizeof(errbuf),
                    "fork: %s", strerror(errno));
#endif
                (void) close(fd);
                return (errbuf);
            }
            if (cpid) {    /* parent */
                (void) close(fd);
                return (NULL);
            }
            forked++;
            /* wait at most 5 minutes */
            (void) signal(SIGALRM, SIG_DFL);
            (void) signal(SIGTERM, SIG_DFL); /* XXX */
            (void) sigsetmask(0);
            (void) alarm((u_int)(60 * 5));
            (void) fcntl(fd, O_NONBLOCK, &off);
            continue;
        }
        /*
         * We get ENODEV on a slip line if we're running as root,
         * and EIO if the line just went away.
         */
        if (errno == ENODEV || errno == EIO)
            break;
        (void) close(fd);
        if (forked)
            _exit(1);
#ifdef __linux__
        (void) sprintf(errbuf,
            "%s: %s", device, strerror(errno));
#else
        (void) snprintf(errbuf, sizeof(errbuf),
            "%s: %s", device, strerror(errno));
#endif
        return (errbuf);
    }

    (void) close(fd);
    if (forked)
        _exit(0);
    return (NULL);
}