bin/ln/ln.c

   1 /*-
   2  * Copyright (c) 1987, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#) Copyright (c) 1987, 1993, 1994 The Regents of the University of California.  All rights reserved.
  30  * @(#)ln.c     8.2 (Berkeley) 3/31/94
  31  * $FreeBSD: head/bin/ln/ln.c 251261 2013-06-02 17:55:00Z eadler $
  32  */
  33
  34 #include <sys/param.h>
  35 #include <sys/stat.h>
  36
  37 #include <err.h>
  38 #include <errno.h>
  39 #include <fcntl.h>
  40 #include <libgen.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45
  46 static int      fflag;                  /* Unlink existing files. */
  47 static int      Fflag;                  /* Remove empty directories also. */
  48 static int      hflag;                  /* Check new name for symlink first. */
  49 static int      iflag;                  /* Interactive mode. */
  50 static int      Pflag;                  /* Create hard links to symlinks. */
  51 static int      sflag;                  /* Symbolic, not hard, link. */
  52 static int      vflag;                  /* Verbose output. */
  53 static int      wflag;                  /* Warn if symlink target does not
  54                                          * exist, and -f is not enabled. */
  55 static char     linkch;
  56
  57 static int      linkit(const char *, const char *, int);
  58 static void     usage(void);
  59
  60 int
  61 main(int argc, char *argv[])
  62 {
  63         struct stat sb;
  64         char *p, *targetdir;
  65         int ch, exitval;
  66
  67         /*
  68          * Test for the special case where the utility is called as
  69          * "link", for which the functionality provided is greatly
  70          * simplified.
  71          */
  72         if ((p = strrchr(argv[0], '/')) == NULL)
  73                 p = argv[0];
  74         else
  75                 ++p;
  76         if (strcmp(p, "link") == 0) {
  77                 while (getopt(argc, argv, "") != -1)
  78                         usage();
  79                 argc -= optind;
  80                 argv += optind;
  81                 if (argc != 2)
  82                         usage();
  83                 exit(linkit(argv[0], argv[1], 0));
  84         }
  85
  86         while ((ch = getopt(argc, argv, "FLPfhinsvw")) != -1)
  87                 switch (ch) {
  88                 case 'F':
  89                         Fflag = 1;
  90                         break;
  91                 case 'L':
  92                         Pflag = 0;
  93                         break;
  94                 case 'P':
  95                         Pflag = 1;
  96                         break;
  97                 case 'f':
  98                         fflag = 1;
  99                         iflag = 0;
 100                         wflag = 0;
 101                         break;
 102                 case 'h':
 103                 case 'n':
 104                         hflag = 1;
 105                         break;
 106                 case 'i':
 107                         iflag = 1;
 108                         fflag = 0;
 109                         break;
 110                 case 's':
 111                         sflag = 1;
 112                         break;
 113                 case 'v':
 114                         vflag = 1;
 115                         break;
 116                 case 'w':
 117                         wflag = 1;
 118                         break;
 119                 case '?':
 120                 default:
 121                         usage();
 122                 }
 123
 124         argv += optind;
 125         argc -= optind;
 126
 127         linkch = sflag ? '-' : '=';
 128         if (sflag == 0)
 129                 Fflag = 0;
 130         if (Fflag == 1 && iflag == 0) {
 131                 fflag = 1;
 132                 wflag = 0;              /* Implied when fflag != 0 */
 133         }
 134
 135         switch(argc) {
 136         case 0:
 137                 usage();
 138                 /* NOTREACHED */
 139         case 1:                         /* ln source */
 140                 exit(linkit(argv[0], ".", 1));
 141         case 2:                         /* ln source target */
 142                 exit(linkit(argv[0], argv[1], 0));
 143         default:
 144                 ;
 145         }
 146                                         /* ln source1 source2 directory */
 147         targetdir = argv[argc - 1];
 148         if (hflag && lstat(targetdir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
 149                 /*
 150                  * We were asked not to follow symlinks, but found one at
 151                  * the target--simulate "not a directory" error
 152                  */
 153                 errno = ENOTDIR;
 154                 err(1, "%s", targetdir);
 155         }
 156         if (stat(targetdir, &sb))
 157                 err(1, "%s", targetdir);
 158         if (!S_ISDIR(sb.st_mode))
 159                 usage();
 160         for (exitval = 0; *argv != targetdir; ++argv)
 161                 exitval |= linkit(*argv, targetdir, 1);
 162         exit(exitval);
 163 }
 164
 165 /*
 166  * Two pathnames refer to the same directory entry if the directories match
 167  * and the final components' names match.
 168  */
 169 static int
 170 samedirent(const char *path1, const char *path2)
 171 {
 172         const char *file1, *file2;
 173         char pathbuf[PATH_MAX];
 174         struct stat sb1, sb2;
 175
 176         if (strcmp(path1, path2) == 0)
 177                 return 1;
 178         file1 = strrchr(path1, '/');
 179         if (file1 != NULL)
 180                 file1++;
 181         else
 182                 file1 = path1;
 183         file2 = strrchr(path2, '/');
 184         if (file2 != NULL)
 185                 file2++;
 186         else
 187                 file2 = path2;
 188         if (strcmp(file1, file2) != 0)
 189                 return 0;
 190         if (file1 - path1 >= PATH_MAX || file2 - path2 >= PATH_MAX)
 191                 return 0;
 192         if (file1 == path1)
 193                 memcpy(pathbuf, ".", 2);
 194         else {
 195                 memcpy(pathbuf, path1, file1 - path1);
 196                 pathbuf[file1 - path1] = '\0';
 197         }
 198         if (stat(pathbuf, &sb1) != 0)
 199                 return 0;
 200         if (file2 == path2)
 201                 memcpy(pathbuf, ".", 2);
 202         else {
 203                 memcpy(pathbuf, path2, file2 - path2);
 204                 pathbuf[file2 - path2] = '\0';
 205         }
 206         if (stat(pathbuf, &sb2) != 0)
 207                 return 0;
 208         return sb1.st_dev == sb2.st_dev && sb1.st_ino == sb2.st_ino;
 209 }
 210
 211 static int
 212 linkit(const char *source, const char *target, int isdir)
 213 {
 214         struct stat sb;
 215         const char *p;
 216         int ch, exists, first;
 217         char path[PATH_MAX];
 218         char wbuf[PATH_MAX];
 219         char bbuf[PATH_MAX];
 220
 221         if (!sflag) {
 222                 /* If source doesn't exist, quit now. */
 223                 if ((Pflag ? lstat : stat)(source, &sb)) {
 224                         warn("%s", source);
 225                         return (1);
 226                 }
 227                 /* Only symbolic links to directories. */
 228                 if (S_ISDIR(sb.st_mode)) {
 229                         errno = EISDIR;
 230                         warn("%s", source);
 231                         return (1);
 232                 }
 233         }
 234
 235         /*
 236          * If the target is a directory (and not a symlink if hflag),
 237          * append the source's name.
 238          */
 239         if (isdir ||
 240             (lstat(target, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
 241             (!hflag && stat(target, &sb) == 0 && S_ISDIR(sb.st_mode))) {
 242                 if (strlcpy(bbuf, source, sizeof(bbuf)) >= sizeof(bbuf) ||
 243                     (p = basename(bbuf)) == NULL ||
 244                     snprintf(path, sizeof(path), "%s/%s", target, p) >=
 245                     (ssize_t)sizeof(path)) {
 246                         errno = ENAMETOOLONG;
 247                         warn("%s", source);
 248                         return (1);
 249                 }
 250                 target = path;
 251         }
 252
 253         /*
 254          * If the link source doesn't exist, and a symbolic link was
 255          * requested, and -w was specified, give a warning.
 256          */
 257         if (sflag && wflag) {
 258                 if (*source == '/') {
 259                         /* Absolute link source. */
 260                         if (stat(source, &sb) != 0)
 261                                  warn("warning: %s inaccessible", source);
 262                 } else {
 263                         /*
 264                          * Relative symlink source.  Try to construct the
 265                          * absolute path of the source, by appending `source'
 266                          * to the parent directory of the target.
 267                          */
 268                         strlcpy(bbuf, target, sizeof(bbuf));
 269                         p = dirname(bbuf);
 270                         if (p != NULL) {
 271                                 snprintf(wbuf, sizeof(wbuf), "%s/%s",
 272                                     p, source);
 273                                 if (stat(wbuf, &sb) != 0)
 274                                         warn("warning: %s", source);
 275                         }
 276                 }
 277         }
 278
 279         /*
 280          * If the file exists, first check it is not the same directory entry.
 281          */
 282         exists = !lstat(target, &sb);
 283         if (exists) {
 284                 if (!sflag && samedirent(source, target)) {
 285                         warnx("%s and %s are the same directory entry",
 286                             source, target);
 287                         return (1);
 288                 }
 289         }
 290         /*
 291          * Then unlink it forcibly if -f was specified
 292          * and interactively if -i was specified.
 293          */
 294         if (fflag && exists) {
 295                 if (Fflag && S_ISDIR(sb.st_mode)) {
 296                         if (rmdir(target)) {
 297                                 warn("%s", target);
 298                                 return (1);
 299                         }
 300                 } else if (unlink(target)) {
 301                         warn("%s", target);
 302                         return (1);
 303                 }
 304         } else if (iflag && exists) {
 305                 fflush(stdout);
 306                 fprintf(stderr, "replace %s? ", target);
 307
 308                 first = ch = getchar();
 309                 while(ch != '\n' && ch != EOF)
 310                         ch = getchar();
 311                 if (first != 'y' && first != 'Y') {
 312                         fprintf(stderr, "not replaced\n");
 313                         return (1);
 314                 }
 315
 316                 if (Fflag && S_ISDIR(sb.st_mode)) {
 317                         if (rmdir(target)) {
 318                                 warn("%s", target);
 319                                 return (1);
 320                         }
 321                 } else if (unlink(target)) {
 322                         warn("%s", target);
 323                         return (1);
 324                 }
 325         }
 326
 327         /* Attempt the link. */
 328         if (sflag ? symlink(source, target) :
 329             linkat(AT_FDCWD, source, AT_FDCWD, target,
 330             Pflag ? 0 : AT_SYMLINK_FOLLOW)) {
 331                 warn("%s", target);
 332                 return (1);
 333         }
 334         if (vflag)
 335                 printf("%s %c> %s\n", target, linkch, source);
 336         return (0);
 337 }
 338
 339 static void
 340 usage(void)
 341 {
 342         fprintf(stderr, "%s\n%s\n%s\n",
 343             "usage: ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file [target_file]",
 344             "       ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file ... target_dir",
 345             "       link source_file target_file");
 346         exit(1);
 347 }