usr/src/lib/libcmd/common/readlink.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1982-2007 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                                                                      *
  20 ***********************************************************************/
  21 #pragma prototyped
  22
  23 static const char usage[] =
  24 "[-?\n@(#)$Id: readlink (AT&T Research) 2008-06-08 $\n]"
  25 USAGE_LICENSE
  26 "[+NAME?readlink - read the contents of a symbolic link]"
  27 "[+DESCRIPTION?\breadlink\b returns the contents of the symbolic "
  28        "link referred to by the path argument. Unless the \b-f\b "
  29        "option is specified an error will be returned when the path "
  30        "is not a symbolic link.]"
  31 "[f:canonicalize?The returned value will be an absolute pathname that names "
  32        "the same file, whose resolution does not involve \".\", \"..\", or "
  33        "symbolic links, otherwise only the exact (relative) value will be returned.]"
  34 "[n:no-newline?Supress newline at the end.]"
  35 "[v:verbose?Verbose - print errors.]"
  36 "[+SEE ALSO?\bbasename\b(1),\bdirname\b(2),\breadlink\b(2),\breadpath\n(2)]"
  37 ;
  38
  39 #include <cmd.h>
  40
  41 int
  42 b_readlink(int argc, char** argv, void* context)
  43 {
  44        register char*          s;
  45        register int            i;
  46        register char*          m;
  47        register char*          x;
  48        int                     canonicalize = 0,
  49                                nonewline = 0,
  50                                verbose = 0;
  51        char                    buf[PATH_MAX+2];
  52        int                     len = 0;
  53        char                   *filename,
  54                               *resolvedname = NULL;
  55
  56        cmdinit(argc, argv, context, ERROR_CATALOG, 0);
  57        for (;;)
  58        {
  59                switch (optget(argv, usage))
  60                {
  61                case 'f':
  62                        canonicalize = opt_info.num;
  63                        continue;
  64                case 'n':
  65                        nonewline = opt_info.num;
  66                        continue;
  67                case 'v':
  68                        verbose = opt_info.num;
  69                        continue;
  70                case '?':
  71                        error(ERROR_usage(2), "%s", opt_info.arg);
  72                        continue;
  73                case ':':
  74                        error(2, "%s", opt_info.arg);
  75                        continue;
  76                }
  77                break;
  78        }
  79        argv += opt_info.index;
  80        argc -= opt_info.index;
  81        if(error_info.errors || argc != 1)
  82                error(ERROR_usage(2),"%s", optusage(NiL));
  83        filename = argv[0];
  84
  85        if (canonicalize)
  86        {
  87                len = resolvepath(filename, buf, sizeof(buf)-2);
  88        }
  89        else
  90        {
  91                len = readlink(filename, buf, sizeof(buf)-2);
  92        }
  93
  94        if (len != -1)
  95                resolvedname = buf;
  96
  97        if (!resolvedname)
  98        {
  99                if (verbose)
 100                        error(ERROR_system(1),"%s: readlink failed", filename);
 101                else
 102                        return 1;
 103        }
 104
 105        if (!nonewline)
 106                resolvedname[len++] = '\n';
 107
 108        sfwrite(sfstdout, resolvedname, len);
 109
 110        return 0;
 111 }