mail.c

操作系统源代码

  char *p, *q;

  /* Here we copy until we reach the end of the letter (end of file or
   * a line containing only a '.'). Postmarks (lines beginning with
   * "From ") are copied with a ">" prepended. Here we also complicate
   * things by not setting a line limit. */
  state = '\n';
  p = postmark;
  while (EOF != (c = getc(fromfp))) {
	switch (state) {
	    case '\n':
		if ('.' == c)	/* '.' at BOL */
			state = '.';
		else if (*p == c) {	/* start of postmark */
			++p;
			state = 'P';
		} else {	/* anything else */
			if ('\n' == c)
				blankline = 1;
			else {
				state = '\0';
				blankline = 0;
			}
			putc(c, tofp);
		}
		break;
	    case '.':
		if ('\n' == c) goto done;
		state = '\0';
		putc('.', tofp);
		putc(c, tofp);
		break;
	    case 'P':
		if (*p == c) {
			if (*++p == '\0') {	/* successfully reached end */
				p = postmark;
				putc('>', tofp);
				fputs(postmark, tofp);
				state = '\0';
				break;
			}
			break;	/* not there yet */
		}
		state = ('\n' == c) ? '\n' : '\0';
		for (q = postmark; q < p; ++q) putc(*q, tofp);
		putc(c, tofp);
		blankline = 0;
		p = postmark;
		break;
	    default:
		state = ('\n' == c) ? '\n' : '\0';
		putc(c, tofp);
	}
  }
  if ('\n' != state) putc('\n', tofp);
done:
  if (!blankline) putc('\n', tofp);
  if (ferror(tofp)) return -1;
  return 0;
}

void readbox()
{
  char linebuf[512];
  struct letter *let;
  off_t current;

  firstlet = lastlet = NULL;

  if (access(mailbox, 4) < 0 || NULL == (boxfp = fopen(mailbox, "r"))) {
	if (usedrop && ENOENT == errno) return;
	fprintf(stderr, "can't access mailbox ");
	perror(mailbox);
	exit(1);
  }
  current = 0L;
  while (1) {
	if (NULL == fgets(linebuf, sizeof linebuf, boxfp)) break;

	if (!strncmp(linebuf, "From ", (size_t)5)) {
		if (NULL == (let = (struct letter *) malloc(sizeof(struct letter)))) {
			fprintf(stderr, "Out of memory.\n");
			exit(1);
		}
		if (NULL == lastlet) {
			firstlet = let;
			let->prev = NULL;
		} else {
			let->prev = lastlet;
			lastlet->next = let;
		}
		lastlet = let;
		let->next = NULL;

		let->status = UNREAD;
		let->location = current;
		D(printf("letter at %ld\n", current));
	}
	current += strlen(linebuf);
  }
}

void printall()
{
  struct letter *let;

  let = reversemode ? firstlet : lastlet;

  if (NULL == let) {
	printf("No mail.\n");
	return;
  }
  while (NULL != let) {
	printlet(let, stdout);
	let = reversemode ? let->next : let->prev;
  }
}

void interact()
{
  char linebuf[512];		/* user input line */
  struct letter *let, *next;	/* current and next letter */
  int interrupted = 0;		/* SIGINT hit during letter print */
  int needprint = 1;		/* need to print this letter */
  char *savefile;		/* filename to save into */

  if (NULL == firstlet) {
	printf("No mail.\n");
	return;
  }
  let = reversemode ? firstlet : lastlet;

  while (1) {
	next = reversemode ? let->next : let->prev;
	if (NULL == next) next = let;

	if (!quitmode) {
		interrupted = setjmp(printjump);
		signal(SIGINT, onint);
	}
	if (!interrupted && needprint) {
		if (DELETED != let->status) let->status = READ;
		printlet(let, stdout);
	}
	if (interrupted) putchar('\n');
	needprint = 0;
	fputs(PROMPT, stdout);
	fflush(stdout);

	if (fgets(linebuf, sizeof linebuf, stdin) == NULL) break;

	if (!quitmode) signal(SIGINT, SIG_IGN);

	switch (linebuf[0]) {
	    case '\n':
		let = next;
		needprint = 1;
		continue;
	    case 'd':
		let->status = DELETED;
		if (next != let)/* look into this */
			needprint = 1;
		needupdate = 1;
		let = next;
		continue;
	    case 'p':
		needprint = 1;
		continue;
	    case '-':
		next = reversemode ? let->prev : let->next;
		if (NULL == next) next = let;
		let = next;
		needprint = 1;
		continue;
	    case 's':
		for (savefile = strtok(linebuf + 1, " \t\n");
		     savefile != NULL;
		     savefile = strtok((char *) NULL, " \t\n")) {
			savelet(let, savefile);
		}
		continue;
	    case '!':
		doshell(linebuf + 1);
		continue;
	    case '*':
		dohelp();
		continue;
	    case 'q':
		return;
	    case 'x':
		exit(0);
	    default:
		fprintf(stderr, "Illegal command\n");
		continue;
	}
  }
}

void onint(dummy)
int dummy;	/* to satisfy ANSI compilers */
{
  longjmp(printjump, 1);
}

void savelet(let, savefile)
struct letter *let;
char *savefile;
{
  int waitstat, pid;
  FILE *savefp;

  if ((pid = fork()) < 0) {
	perror("mail: couldn't fork");
	return;
  } else if (pid != 0) {	/* parent */
	wait(&waitstat);
	return;
  }

  /* Child */
  setgid(getgid());
  setuid(getuid());
  if ((savefp = fopen(savefile, "a")) == NULL) {
	perror(savefile);
	exit(0);
  }
  printlet(let, savefp);
  if ((ferror(savefp) != 0) | (fclose(savefp) != 0)) {
	fprintf(stderr, "savefile write error:");
	perror(savefile);
  }
  exit(0);
}

void updatebox()
{
  FILE *tempfp;			/* fp for tempfile */
  char lockname[PATHLEN];	/* maildrop lock */
  int locktries = 0;		/* tries when box is locked */
  struct letter *let;		/* current letter */
  int c;

  sprintf(lockname, LOCKNAME, whoami());

  if (NULL == (tempfp = fopen(tempname, "w"))) {
	perror("mail: can't create temporary file");
	return;
  }
  for (let = firstlet; let != NULL; let = let->next) {
	if (let->status != DELETED) {
		printlet(let, tempfp);
		D(printf("printed letter at %ld\n", let->location));
	}
  }

  if (ferror(tempfp) || NULL == (tempfp = freopen(tempname, "r", tempfp))) {
	perror("mail: temporary file write error");
	unlink(tempname);
	return;
  }

  /* Shut off signals during the update */
  signal(SIGINT, SIG_IGN);
  signal(SIGHUP, SIG_IGN);
  signal(SIGQUIT, SIG_IGN);

  if (usedrop) while (link(mailbox, lockname) != 0) {
		if (++locktries >= LOCKTRIES) {
			fprintf(stderr, "mail: couldn't lock maildrop for update\n");
			return;
		}
		sleep(LOCKWAIT);
	}

  if (NULL == (boxfp = freopen(mailbox, "w", boxfp))) {
	perror("mail: couldn't reopen maildrop");
	fprintf(stderr, "mail may have been lost; look in %s\n", tempname);
	if (usedrop) unlink(lockname);
	return;
  }
  unlink(tempname);

  while ((c = getc(tempfp)) != EOF) putc(c, boxfp);

  fclose(boxfp);

  if (usedrop) unlink(lockname);
}

void printlet(let, tofp)
struct letter *let;
FILE *tofp;
{
  off_t current, limit;
  int c;

  fseek(boxfp, (current = let->location), 0);
  limit = (NULL != let->next) ? let->next->location : -1;

  while (current != limit && (c = getc(boxfp)) != EOF) {
	putc(c, tofp);
	++current;
  }
}

void doshell(command)
char *command;
{
  int waitstat, pid;
  char *shell;

  if (NULL == (shell = getenv("SHELL"))) shell = SHELL;

  if ((pid = fork()) < 0) {
	perror("mail: couldn't fork");
	return;
  } else if (pid != 0) {	/* parent */
	wait(&waitstat);
	return;
  }

  /* Child */
  setgid(getgid());
  setuid(getuid());
  umask(oldmask);

  execl(shell, shell, "-c", command, (char *) NULL);
  fprintf(stderr, "can't exec shell\n");
  exit(127);
}

void usage()
{
  fprintf(stderr, "usage: mail [-v] user [...]\n");
  fprintf(stderr, "       mail [-epqr] [-f file] [-t arg]\n");
}

char *basename(name)
char *name;
{
  char *p;

  if (NULL == (p = rindex(name, '/')))
	return name;
  else
	return p + 1;
}

char *whoami()
{
  struct passwd *pw;

  if (NULL != (pw = getpwuid(getuid())))
	return pw->pw_name;
  else
	return "nobody";
}

void dohelp()
{
  FILE *fp;
  char buffer[80];

  if ( (fp = fopen(HELPFILE, "r")) == NULL)
	fprintf(stdout, "can't open helpfile %s\n", HELPFILE);
  else
	while (fgets(buffer, 80, fp))
		fputs(buffer, stdout);
}

int filesize(name)
char *name ;
{
  struct stat buf;
 
  if (stat(name, &buf) == -1)
	buf.st_size = 0L;

  return (buf.st_size ? 1 : 0);
}