chmod.c

操作系统源代码

/* chmod - Change file modes				Author: V. Archer */

/* Copyright 1991 by Vincent Archer
 *	You may freely redistribute this software, in source or binary
 *	form, provided that you do not alter this copyright mention in any
 *	way.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <minix/minlib.h>
#include <stdio.h>

#ifndef S_ISLNK
#define S_ISLNK(mode)	0
#define lstat		stat
#endif

#define USR_MODES (S_ISUID|S_IRWXU)
#define GRP_MODES (S_ISGID|S_IRWXG)
#define EXE_MODES (S_IXUSR|S_IXGRP|S_IXOTH)
#ifdef S_ISVTX
#define ALL_MODES (USR_MODES|GRP_MODES|S_IRWXO|S_ISVTX)
#else
#define ALL_MODES (USR_MODES|GRP_MODES|S_IRWXO)
#endif


/* Common variables */
char *symbolic;
mode_t new_mode, u_mask;
int rflag, errors;
struct stat st;
char path[PATH_MAX + 1];

_PROTOTYPE(int main, (int argc, char **argv));
_PROTOTYPE(mode_t parsemode, (char *symbolic, Mode_t oldmode));
_PROTOTYPE(int do_change, (char *name));
_PROTOTYPE(void usage, (void));

/* Parse a P1003.2 4.7.7-conformant symbolic mode. */
mode_t parsemode(symbolic, oldmode)
char *symbolic;
mode_t oldmode;
{
  mode_t who, mask, newmode, tmpmask;
  char action;

  newmode = oldmode & ALL_MODES;
  while (*symbolic) {
	who = 0;
	for (; *symbolic; symbolic++) {
		if (*symbolic == 'a') {
			who |= ALL_MODES;
			continue;
		}
		if (*symbolic == 'u') {
			who |= USR_MODES;
			continue;
		}
		if (*symbolic == 'g') {
			who |= GRP_MODES;
			continue;
		}
		if (*symbolic == 'o') {
			who |= S_IRWXO;
			continue;
		}
		break;
	}
	if (!*symbolic || *symbolic == ',') usage();
	while (*symbolic) {
		if (*symbolic == ',') break;
		switch (*symbolic) {
		    default:
			usage();
		    case '+':
		    case '-':
		    case '=':	action = *symbolic++;
		}
		mask = 0;
		for (; *symbolic; symbolic++) {
			if (*symbolic == 'u') {
				tmpmask = newmode & S_IRWXU;
				mask |= tmpmask | (tmpmask << 3) | (tmpmask << 6);
				symbolic++;
				break;
			}
			if (*symbolic == 'g') {
				tmpmask = newmode & S_IRWXG;
				mask |= tmpmask | (tmpmask >> 3) | (tmpmask << 3);
				symbolic++;
				break;
			}
			if (*symbolic == 'o') {
				tmpmask = newmode & S_IRWXO;
				mask |= tmpmask | (tmpmask >> 3) | (tmpmask >> 6);
				symbolic++;
				break;
			}
			if (*symbolic == 'r') {
				mask |= S_IRUSR | S_IRGRP | S_IROTH;
				continue;
			}
			if (*symbolic == 'w') {
				mask |= S_IWUSR | S_IWGRP | S_IWOTH;
				continue;
			}
			if (*symbolic == 'x') {
				mask |= EXE_MODES;
				continue;
			}
			if (*symbolic == 's') {
				mask |= S_ISUID | S_ISGID;
				continue;
			}
			if (*symbolic == 'X') {
				if (S_ISDIR(oldmode) || (oldmode & EXE_MODES))
					mask |= EXE_MODES;
				continue;
			}
#ifdef S_ISVTX
			if (*symbolic == 't') {
				mask |= S_ISVTX;
				who |= S_ISVTX;
				continue;
			}
#endif
			break;
		}
		switch (action) {
		    case '=':
			if (who)
				newmode &= ~who;
			else
				newmode = 0;
		    case '+':
			if (who)
				newmode |= who & mask;
			else
				newmode |= mask & (~u_mask);
			break;
		    case '-':
			if (who)
				newmode &= ~(who & mask);
			else
				newmode &= ~mask | u_mask;
		}
	}
	if (*symbolic) symbolic++;
  }
  return(newmode);
}


/* Main module. The single option possible (-R) does not warrant a call to
 * the getopt() stuff.
 */
int main(argc, argv)
int argc;
char *argv[];
{
  int ex_code = 0;

  argc--;
  argv++;

  if (argc && strcmp(*argv, "-R") == 0) {
	argc--;
	argv++;
	rflag = 1;
  } else
	rflag = 0;

  if (!argc--) usage();
  if (!strcmp(argv[0], "--")) {	/* Allow chmod -- -r, as in Draft11 example */
	if (!argc--) usage();
	argv++;
  }
  symbolic = *argv++;
  if (!argc) usage();

  if (*symbolic >= '0' && *symbolic <= '7') {
	new_mode = 0;
	while (*symbolic >= '0' && *symbolic <= '7')
		new_mode = (new_mode << 3) | (*symbolic++ & 07);
	if (*symbolic) usage();
	new_mode &= ALL_MODES;
	symbolic = (char *) 0;
  } else
	u_mask = umask(0);

  while (argc--)
	if (do_change(*argv++)) ex_code = 1;
  return(ex_code);
}


/* Apply a mode change to a given file system element. */
int do_change(name)
char *name;
{
  mode_t m;
  DIR *dirp;
  struct dirent *entp;
  char *namp;

  if (lstat(name, &st)) {
	perror(name);
	return(1);
  }
  if (S_ISLNK(st.st_mode) && rflag) return(0);	/* Note: violates POSIX. */
  if (!symbolic)
	m = new_mode;
  else
	m = parsemode(symbolic, st.st_mode);
  if (chmod(name, m)) {
	perror(name);
	errors = 1;
  } else
	errors = 0;

  if (S_ISDIR(st.st_mode) && rflag) {
	if (!(dirp = opendir(name))) {
		perror(name);
		return(1);
	}
	if (name != path) strcpy(path, name);
	namp = path + strlen(path);
	*namp++ = '/';
	while (entp = readdir(dirp))
		if (entp->d_name[0] != '.' ||
		    (entp->d_name[1] &&
		     (entp->d_name[1] != '.' || entp->d_name[2]))) {
			strcpy(namp, entp->d_name);
			errors |= do_change(path);
		}
	closedir(dirp);
	*--namp = '\0';
  }
  return(errors);
}


/* Display Posix prototype */
void usage()
{
  std_err("Usage: chmod [-R] mode file...\n");
  exit(1);
}