wall.c

sysvinit--linux系统下的init

/*
 * wall.c	Write to all users logged in.
 *
 * Usage:	wall [text]
 *
 * Version:	@(#)wall  2.79  12-Sep-2000  [e-mail]
 *
 *		This file is part of the sysvinit suite,
 *		Copyright 1991-2000 Miquel van Smoorenburg.
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <pwd.h>
#include <syslog.h>


char *Version = "@(#) wall 2.79 12-Sep-2000 [e-mail]";
#define MAXLEN 4096
#define MAXLINES 20

extern void wall(char *, int, int);

int main(int argc, char **argv)
{
  char buf[MAXLEN];
  char line[83];
  int i, f, ch;
  int len = 0;
  int remote = 0;
  char *p;
  char *whoami;
  struct passwd *pwd;

  buf[0] = 0;
  if ((pwd = getpwuid(getuid())) == NULL) {
	if (getuid() == 0)
		whoami = "root";
	else {
		fprintf(stderr, "You don't exist. Go away.\n");
		exit(1);
	}
  } else
	whoami = pwd->pw_name;

  while((ch = getopt(argc, argv, "n")) != EOF)
	switch(ch) {
		case 'n':
			/*
			 *	Undocumented option for suppressing
			 *	banner from rpc.rwalld. Only works if
			 *	we are root or if we're NOT setgid.
			 */
			if (geteuid() != 0 && getgid() != getegid()) {
				fprintf(stderr, "wall -n: not priviliged\n");
				exit(1);
			}
			remote = 1;
			break;
		default:
			fprintf(stderr, "usage: wall [message]\n");
			return 1;
			break;
	}

  if ((argc - optind) > 0) {
	for(f = optind; f < argc; f++) {
		len += strlen(argv[f]) + 1;
		if (len >= MAXLEN-2) break;
		strcat(buf, argv[f]);
		if (f < argc-1) strcat(buf, " ");
	}
	strcat(buf, "\r\n");
  } else {
	while(fgets(line, 80, stdin)) {
		/*
		 *	Make sure that line ends in \r\n
		 */
		for(p = line; *p && *p != '\r' && *p != '\n'; p++)
			;
		strcpy(p, "\r\n");
		len += strlen(line);
		if (len >= MAXLEN) break;
		strcat(buf, line);
	}
  }

  i = 0;
  for (p = buf; *p; p++) {
	if (*p == '\n' && i++ > MAXLINES) {
		*++p = 0;
		break;
	}
  }

  openlog("wall", LOG_PID, LOG_USER);
  syslog(LOG_INFO, "wall: user %s broadcasted %d lines (%d chars)",
	whoami, i, strlen(buf));
  closelog();

  unsetenv("TZ");
  wall(buf, 0, remote);

  /*NOTREACHED*/
  return 0;
}