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[unix-history] / usr / src / usr.bin / wall / ttymsg.c

/*
* Copyright (c) 1989 The Regents of the University of California.
* All rights reserved.
*
* %sccs.include.redist.c%
*/

#ifndef lint
static char sccsid[] = "@(#)ttymsg.c    5.9 (Berkeley) %G%";
#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),
* syslogd(8), and talk(1).  Forks and finishes in child if write would block, 
* waiting up to tmout seconds.  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, tmout)
       struct iovec *iov;
       int iovcnt;
       char *line;
       int tmout;
{
       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);
               (void) snprintf(errbuf, sizeof(errbuf),
                   "%s: %s", device, strerror(errno));
               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) {
                               (void) snprintf(errbuf, sizeof(errbuf),
                                   "fork: %s", strerror(errno));
                               (void) close(fd);
                               return (errbuf);
                       }
                       if (cpid) {     /* parent */
                               (void) close(fd);
                               return (NULL);
                       }
                       forked++;
                       /* wait at most tmout seconds */
                       (void) signal(SIGALRM, SIG_DFL);
                       (void) signal(SIGTERM, SIG_DFL); /* XXX */
                       (void) sigsetmask(0);
                       (void) alarm((u_int)tmout);
                       (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);
               (void) snprintf(errbuf, sizeof(errbuf),
                   "%s: %s", device, strerror(errno));
               return (errbuf);
       }

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