1 /* readlink -- display value of a symbolic link.
2 Copyright (C) 2002-2023 Free Software Foundation, Inc.
3
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation, either version 3 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 /* Written by Dmitry V. Levin */
18
19 #include <config.h>
20 #include <stdio.h>
21 #include <getopt.h>
22 #include <sys/types.h>
23
24 #include "system.h"
25 #include "canonicalize.h"
26 #include "areadlink.h"
27
28 /* The official name of this program (e.g., no 'g' prefix). */
29 #define PROGRAM_NAME "readlink"
30
31 #define AUTHORS proper_name ("Dmitry V. Levin")
32
33 /* If true, do not output the trailing newline. */
34 static bool no_newline;
35
36 /* If true, report error messages. */
37 static bool verbose;
38
39 static struct option const longopts[] =
40 {
41 {"canonicalize", no_argument, nullptr, 'f'},
42 {"canonicalize-existing", no_argument, nullptr, 'e'},
43 {"canonicalize-missing", no_argument, nullptr, 'm'},
44 {"no-newline", no_argument, nullptr, 'n'},
45 {"quiet", no_argument, nullptr, 'q'},
46 {"silent", no_argument, nullptr, 's'},
47 {"verbose", no_argument, nullptr, 'v'},
48 {"zero", no_argument, nullptr, 'z'},
49 {GETOPT_HELP_OPTION_DECL},
50 {GETOPT_VERSION_OPTION_DECL},
51 {nullptr, 0, nullptr, 0}
52 };
53
54 void
55 usage (int status)
56 {
57 if (status != EXIT_SUCCESS)
58 emit_try_help ();
59 else
60 {
61 printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
62 fputs (_("Print value of a symbolic link or canonical file name\n\n"),
63 stdout);
64 fputs (_("\
65 -f, --canonicalize canonicalize by following every symlink in\n\
66 every component of the given name recursively;\
67 \n\
68 all but the last component must exist\n\
69 -e, --canonicalize-existing canonicalize by following every symlink in\n\
70 every component of the given name recursively,\
71 \n\
72 all components must exist\n\
73 "), stdout);
74 fputs (_("\
75 -m, --canonicalize-missing canonicalize by following every symlink in\n\
76 every component of the given name recursively,\
77 \n\
78 without requirements on components existence\n\
79 -n, --no-newline do not output the trailing delimiter\n\
80 -q, --quiet\n\
81 -s, --silent suppress most error messages (on by default)\n\
82 -v, --verbose report error messages\n\
83 -z, --zero end each output line with NUL, not newline\n\
84 "), stdout);
85 fputs (HELP_OPTION_DESCRIPTION, stdout);
86 fputs (VERSION_OPTION_DESCRIPTION, stdout);
87 emit_ancillary_info (PROGRAM_NAME);
88 }
89 exit (status);
90 }
91
92 int
93 main (int argc, char **argv)
94 {
95 /* If not -1, use this method to canonicalize. */
96 int can_mode = -1;
97 int status = EXIT_SUCCESS;
98 int optc;
99 bool use_nuls = false;
100
101 initialize_main (&argc, &argv);
102 set_program_name (argv[0]);
103 setlocale (LC_ALL, "");
104 bindtextdomain (PACKAGE, LOCALEDIR);
105 textdomain (PACKAGE);
106
107 atexit (close_stdout);
108
109 while ((optc = getopt_long (argc, argv, "efmnqsvz", longopts, nullptr)) != -1)
110 {
111 switch (optc)
112 {
113 case 'e':
114 can_mode = CAN_EXISTING;
115 break;
116 case 'f':
117 can_mode = CAN_ALL_BUT_LAST;
118 break;
119 case 'm':
120 can_mode = CAN_MISSING;
121 break;
122 case 'n':
123 no_newline = true;
124 break;
125 case 'q':
126 case 's':
127 verbose = false;
128 break;
129 case 'v':
130 verbose = true;
131 break;
132 case 'z':
133 use_nuls = true;
134 break;
135 case_GETOPT_HELP_CHAR;
136 case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
137 default:
138 usage (EXIT_FAILURE);
139 }
140 }
141
142 if (optind >= argc)
143 {
144 error (0, 0, _("missing operand"));
145 usage (EXIT_FAILURE);
146 }
147
148 if (argc - optind > 1)
149 {
150 if (no_newline)
151 error (0, 0, _("ignoring --no-newline with multiple arguments"));
152 no_newline = false;
153 }
154
155 for (; optind < argc; ++optind)
156 {
157 char const *fname = argv[optind];
158 char *value = (can_mode != -1
159 ? canonicalize_filename_mode (fname, can_mode)
160 : areadlink_with_size (fname, 63));
161 if (value)
162 {
163 fputs (value, stdout);
164 if (! no_newline)
165 putchar (use_nuls ? '\0' : '\n');
166 free (value);
167 }
168 else
169 {
170 status = EXIT_FAILURE;
171 if (verbose)
172 error (0, errno, "%s", quotef (fname));
173 }
174 }
175
176 return status;
177 }