root/user/bin/ln/ln.c

DEFINITIONS

1. dosymlink
2. dohardlink
3. main

   1 /*
   2  * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
   3  *      The President and Fellows of Harvard College.
   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 UNIVERSITY 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 UNIVERSITY 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  */
  30 #include <unistd.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33 #include <err.h>
  35 /*
  36  * ln - hardlink or symlink files
  37  *
  38  * Usage: ln oldfile newfile
  39  *        ln -s symlinkcontents symlinkfile
  40  */
  43 /*
  44  * Create a symlink with filename PATH that contains text TEXT.
  45  * When fed to ls -l, this produces something that looks like
  46  *
  47  * lrwxrwxrwx  [stuff]   PATH -> TEXT
  48  */
  49 static
  50 void
dosymlink(const char *text, const char *path)
  52 {
  53         if (symlink(text, path)) {
err(1, "%s", path);
  55         }
  56 }
  58 /*
  59  * Create a hard link such that NEWFILE names the same file as
  60  * OLDFILE. Since it's a hard link, the two names for the file
  61  * are equal; both are the "real" file.
  62  */
  63 static
  64 void
dohardlink(const char *oldfile, const char *newfile)
  66 {
  67         if (link(oldfile, newfile)) {
err(1, "%s or %s", oldfile, newfile);
exit(1);
  70         }
  71 }
  73 int
main(int argc, char *argv[])
  75 {
  76         /*
  77          * Just do whatever was asked for.
  78          *
  79          * We don't allow the Unix model where you can do
  80          *    ln [-s] file1 file2 file3 destination-directory
  81          */
  82         if (argc==4 && !strcmp(argv[1], "-s")) {
dosymlink(argv[2], argv[3]);
  84         }
  85         else if (argc==3) {
dohardlink(argv[1], argv[2]);
  87         }
  88         else {
warnx("Usage: ln oldfile newfile");
errx(1, "       ln -s symlinkcontents symlinkfile\n");
  91         }
  92         return 0;
  93 }