1 /* vi: set sw=4 ts=4: */
2 /*
3 * Mini readlink implementation for busybox
4 *
5 * Copyright (C) 2000,2001 Matt Kraai <kraai@alumni.carnegiemellon.edu>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
8 */
9 //config:config READLINK
10 //config: bool "readlink (4 kb)"
11 //config: default y
12 //config: help
13 //config: This program reads a symbolic link and returns the name
14 //config: of the file it points to
15 //config:
16 //config:config FEATURE_READLINK_FOLLOW
17 //config: bool "Enable canonicalization by following all symlinks (-f)"
18 //config: default y
19 //config: depends on READLINK
20 //config: help
21 //config: Enable the readlink option (-f).
22
23 //applet:IF_READLINK(APPLET_NOFORK(readlink, readlink, BB_DIR_USR_BIN, BB_SUID_DROP, readlink))
24
25 //kbuild:lib-$(CONFIG_READLINK) += readlink.o
26
27 //usage:#define readlink_trivial_usage
28 //usage: IF_FEATURE_READLINK_FOLLOW("[-fnv] ") "FILE"
29 //usage:#define readlink_full_usage "\n\n"
30 //usage: "Display the value of a symlink"
31 //usage: IF_FEATURE_READLINK_FOLLOW( "\n"
32 //usage: "\n -f Canonicalize by following all symlinks"
33 //usage: "\n -n Don't add newline"
34 //usage: "\n -v Verbose"
35 //usage: )
36
37 #include "libbb.h"
38
39 /*
40 * # readlink --version
41 * readlink (GNU coreutils) 6.10
42 * # readlink --help
43 * -f, --canonicalize
44 * canonicalize by following every symlink in
45 * every component of the given name recursively;
46 * all but the last component must exist
47 * -e, --canonicalize-existing
48 * canonicalize by following every symlink in
49 * every component of the given name recursively,
50 * all components must exist
51 * -m, --canonicalize-missing
52 * canonicalize by following every symlink in
53 * every component of the given name recursively,
54 * without requirements on components existence
55 * -n, --no-newline do not output the trailing newline
56 * -q, --quiet, -s, --silent suppress most error messages
57 * -v, --verbose report error messages
58 *
59 * bbox supports: -f (partially) -n -v (fully), -q -s (accepts but ignores)
60 * Note: we export the -f flag, but our -f behaves like coreutils' -e.
61 * Unfortunately, there isn't a C lib function we can leverage to get this
62 * behavior which means we'd have to implement the full stack ourselves :(.
63 */
64
65 int readlink_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
readlink_main(int argc UNUSED_PARAM,char ** argv)66 int readlink_main(int argc UNUSED_PARAM, char **argv)
67 {
68 char *buf;
69 char *fname;
70
71 IF_FEATURE_READLINK_FOLLOW(
72 unsigned opt;
73 /* We need exactly one non-option argument. */
74 opt = getopt32(argv, "^" "fnvsq" "\0" "=1");
75 fname = argv[optind];
76 )
77 IF_NOT_FEATURE_READLINK_FOLLOW(
78 const unsigned opt = 0;
79 if (argc != 2) bb_show_usage();
80 fname = argv[1];
81 )
82
83 /* compat: coreutils readlink reports errors silently via exit code */
84 if (!(opt & 4)) /* not -v */
85 logmode = LOGMODE_NONE;
86
87 /* NOFORK: only one alloc is allowed; must free */
88 if (opt & 1) { /* -f */
89 buf = xmalloc_realpath_coreutils(fname);
90 } else {
91 buf = xmalloc_readlink_or_warn(fname);
92 }
93
94 if (!buf)
95 return EXIT_FAILURE;
96 printf((opt & 2) ? "%s" : "%s\n", buf);
97 free(buf);
98
99 fflush_stdout_and_exit(EXIT_SUCCESS);
100 }
101