139 lines
3.1 KiB
C
139 lines
3.1 KiB
C
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/*
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Copyright (C) 2010
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Rocky Bernstein <rocky@gnu.org>
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Diego 'Flameeyes' Pettenò
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Thomas Schmitt
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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Resolves symbolic links.
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To compile as a standalone program:
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gcc -Wall -g -I../.. -DHAVE_CONFIG_H -DSTANDALONE -o follow_symlink follow_symlink.c
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*/
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/*
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Make sure we handle:
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- resolve relative links like /dev/cdrom -> sr2
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- abort on deep link nesting /dev/cdrom -> /dev/cdrom
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*/
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#ifdef HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <ctype.h>
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#ifdef HAVE_STDLIB_H
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# include <stdlib.h>
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#endif
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#include <stdio.h>
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#ifdef HAVE_STRING_H
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# include <string.h>
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#endif
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#ifdef HAVE_UNISTD_H // readlink
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# include <unistd.h>
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#endif
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#ifdef HAVE_INTTYPES_H
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# include "inttypes.h"
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#endif
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#ifdef HAVE_LIMITS_H
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# include <limits.h>
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#endif
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#ifndef PATH_MAX
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#define PATH_MAX 4096
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#endif
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/*!
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Follow symlinks until we have the real device file
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(idea taken from libunieject).
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*/
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void cdio_follow_symlink (const char * src, char * dst) {
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#ifdef HAVE_READLINK
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char tmp_src[PATH_MAX+1];
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char tmp_dst[PATH_MAX+1];
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char *p_adr;
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int link_loop_limit = 100, i;
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int len;
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strcpy(tmp_src, src);
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/* FIXME:
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remove loop and change with stat before and after readlink
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which looks direct symlink. Rely on errno to figure out other
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non-existent or looped symlinks.
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*/
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for(i = 0; i < link_loop_limit; i++) {
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len = readlink(tmp_src, tmp_dst, PATH_MAX);
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if (-1 == len) {
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/* Right now we expect a "not symlink" error. However after
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we put in the stat() suggested above, there won't be a symlink
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error and we should start reporting what the failure is.
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*/
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break;
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} else {
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tmp_dst[len] = '\0';
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if (tmp_dst[0] != '/') {
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/* Take care of relative link like /dev/cdrom -> sr2 */
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p_adr = strrchr(tmp_src, '/');
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if (p_adr != NULL) {
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strncpy(p_adr + 1, tmp_dst, PATH_MAX - (p_adr + 1 - tmp_src));
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} else {
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strncpy(tmp_src, tmp_dst, PATH_MAX);
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}
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} else {
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strncpy(tmp_src, tmp_dst, PATH_MAX);
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}
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tmp_src[PATH_MAX - 1] = 0; /* strncpy() does not always set a 0 */
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}
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}
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strncpy(dst, tmp_src, PATH_MAX);
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#else
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strncpy(dst, src, PATH_MAX);
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#endif
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}
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#ifdef STANDALONE
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int main(int argc, char **argv)
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{
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int i;
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char dest[PATH_MAX];
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if (argc < 2) {
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fprintf(stderr, "Usage: %s path [path ...]\n", argv[0]);
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fprintf(stderr,
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" Resolve symbolic links\n");
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exit(1);
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}
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for (i= 1; i < argc; i++) {
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dest[0] = 0;
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cdio_follow_symlink (argv[i], dest);
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printf("%s -> %s\n", argv[i], dest);
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}
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exit(0);
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}
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#endif
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