1 /* stdbuf -- setup the standard streams for a command
2 Copyright (C) 2009-2023 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 Pádraig Brady. */
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 "assure.h"
26 #include "filenamecat.h"
27 #include "quote.h"
28 #include "xreadlink.h"
29 #include "xstrtol.h"
30 #include "c-ctype.h"
31
32 /* The official name of this program (e.g., no 'g' prefix). */
33 #define PROGRAM_NAME "stdbuf"
34 #define LIB_NAME "libstdbuf.so" /* FIXME: don't hardcode */
35
36 #define AUTHORS proper_name_lite ("Padraig Brady", "P\303\241draig Brady")
37
38 static char *program_path;
39
40 static struct
41 {
42 size_t size;
43 int optc;
44 char *optarg;
45 } stdbuf[3];
46
47 static struct option const longopts[] =
48 {
49 {"input", required_argument, nullptr, 'i'},
50 {"output", required_argument, nullptr, 'o'},
51 {"error", required_argument, nullptr, 'e'},
52 {GETOPT_HELP_OPTION_DECL},
53 {GETOPT_VERSION_OPTION_DECL},
54 {nullptr, 0, nullptr, 0}
55 };
56
57 /* Set size to the value of STR, interpreted as a decimal integer,
58 optionally multiplied by various values.
59 Return -1 on error, 0 on success.
60
61 This supports dd BLOCK size suffixes.
62 Note we don't support dd's b=512, c=1, w=2 or 21x512MiB formats. */
63 static int
64 parse_size (char const *str, size_t *size)
65 {
66 uintmax_t tmp_size;
67 enum strtol_error e = xstrtoumax (str, nullptr, 10,
68 &tmp_size, "EGkKMPQRTYZ0");
69 if (e == LONGINT_OK && SIZE_MAX < tmp_size)
70 e = LONGINT_OVERFLOW;
71
72 if (e == LONGINT_OK)
73 {
74 errno = 0;
75 *size = tmp_size;
76 return 0;
77 }
78
79 errno = (e == LONGINT_OVERFLOW ? EOVERFLOW : errno);
80 return -1;
81 }
82
83 void
84 usage (int status)
85 {
86 if (status != EXIT_SUCCESS)
87 emit_try_help ();
88 else
89 {
90 printf (_("Usage: %s OPTION... COMMAND\n"), program_name);
91 fputs (_("\
92 Run COMMAND, with modified buffering operations for its standard streams.\n\
93 "), stdout);
94
95 emit_mandatory_arg_note ();
96
97 fputs (_("\
98 -i, --input=MODE adjust standard input stream buffering\n\
99 -o, --output=MODE adjust standard output stream buffering\n\
100 -e, --error=MODE adjust standard error stream buffering\n\
101 "), stdout);
102 fputs (HELP_OPTION_DESCRIPTION, stdout);
103 fputs (VERSION_OPTION_DESCRIPTION, stdout);
104 fputs (_("\n\
105 If MODE is 'L' the corresponding stream will be line buffered.\n\
106 This option is invalid with standard input.\n"), stdout);
107 fputs (_("\n\
108 If MODE is '0' the corresponding stream will be unbuffered.\n\
109 "), stdout);
110 fputs (_("\n\
111 Otherwise MODE is a number which may be followed by one of the following:\n\
112 KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G,T,P,E,Z,Y,R,Q.\n\
113 Binary prefixes can be used, too: KiB=K, MiB=M, and so on.\n\
114 In this case the corresponding stream will be fully buffered with the buffer\n\
115 size set to MODE bytes.\n\
116 "), stdout);
117 fputs (_("\n\
118 NOTE: If COMMAND adjusts the buffering of its standard streams ('tee' does\n\
119 for example) then that will override corresponding changes by 'stdbuf'.\n\
120 Also some filters (like 'dd' and 'cat' etc.) don't use streams for I/O,\n\
121 and are thus unaffected by 'stdbuf' settings.\n\
122 "), stdout);
123 emit_exec_status (PROGRAM_NAME);
124 emit_ancillary_info (PROGRAM_NAME);
125 }
126 exit (status);
127 }
128
129 /* argv[0] can be anything really, but generally it contains
130 the path to the executable or just a name if it was executed
131 using $PATH. In the latter case to get the path we can:
132 search getenv("PATH"), readlink("/prof/self/exe"), getenv("_"),
133 dladdr(), pstat_getpathname(), etc. */
134
135 static void
136 set_program_path (char const *arg)
137 {
138 if (strchr (arg, '/')) /* Use absolute or relative paths directly. */
139 {
140 program_path = dir_name (arg);
141 }
142 else
143 {
144 char *path = xreadlink ("/proc/self/exe");
145 if (path)
146 program_path = dir_name (path);
147 else if ((path = getenv ("PATH")))
148 {
149 char *dir;
150 path = xstrdup (path);
151 for (dir = strtok (path, ":"); dir != nullptr;
152 dir = strtok (nullptr, ":"))
153 {
154 char *candidate = file_name_concat (dir, arg, nullptr);
155 if (access (candidate, X_OK) == 0)
156 {
157 program_path = dir_name (candidate);
158 free (candidate);
159 break;
160 }
161 free (candidate);
162 }
163 }
164 free (path);
165 }
166 }
167
168 static int
169 optc_to_fileno (int c)
170 {
171 int ret = -1;
172
173 switch (c)
174 {
175 case 'e':
176 ret = STDERR_FILENO;
177 break;
178 case 'i':
179 ret = STDIN_FILENO;
180 break;
181 case 'o':
182 ret = STDOUT_FILENO;
183 break;
184 }
185
186 return ret;
187 }
188
189 static void
190 set_LD_PRELOAD (void)
191 {
192 int ret;
193 #ifdef __APPLE__
194 char const *preload_env = "DYLD_INSERT_LIBRARIES";
195 #else
196 char const *preload_env = "LD_PRELOAD";
197 #endif
198 char *old_libs = getenv (preload_env);
199 char *LD_PRELOAD;
200
201 /* Note this would auto add the appropriate search path for "libstdbuf.so":
202 gcc stdbuf.c -Wl,-rpath,'$ORIGIN' -Wl,-rpath,$PKGLIBEXECDIR
203 However we want the lookup done for the exec'd command not stdbuf.
204
205 Since we don't link against libstdbuf.so add it to PKGLIBEXECDIR
206 rather than to LIBDIR.
207
208 Note we could add "" as the penultimate item in the following list
209 to enable searching for libstdbuf.so in the default system lib paths.
210 However that would not indicate an error if libstdbuf.so was not found.
211 Also while this could support auto selecting the right arch in a multilib
212 environment, what we really want is to auto select based on the arch of the
213 command being run, rather than that of stdbuf itself. This is currently
214 not supported due to the unusual need for controlling the stdio buffering
215 of programs that are a different architecture to the default on the
216 system (and that of stdbuf itself). */
217 char const *const search_path[] = {
218 program_path,
219 PKGLIBEXECDIR,
220 nullptr
221 };
222
223 char const *const *path = search_path;
224 char *libstdbuf;
225
226 while (true)
227 {
228 struct stat sb;
229
230 if (!**path) /* system default */
231 {
232 libstdbuf = xstrdup (LIB_NAME);
233 break;
234 }
235 ret = asprintf (&libstdbuf, "%s/%s", *path, LIB_NAME);
236 if (ret < 0)
237 xalloc_die ();
238 if (stat (libstdbuf, &sb) == 0) /* file_exists */
239 break;
240 free (libstdbuf);
241
242 ++path;
243 if ( ! *path)
244 error (EXIT_CANCELED, 0, _("failed to find %s"), quote (LIB_NAME));
245 }
246
247 /* FIXME: Do we need to support libstdbuf.dll, c:, '\' separators etc? */
248
249 if (old_libs)
250 ret = asprintf (&LD_PRELOAD, "%s=%s:%s", preload_env, old_libs, libstdbuf);
251 else
252 ret = asprintf (&LD_PRELOAD, "%s=%s", preload_env, libstdbuf);
253
254 if (ret < 0)
255 xalloc_die ();
256
257 free (libstdbuf);
258
259 ret = putenv (LD_PRELOAD);
260 #ifdef __APPLE__
261 if (ret == 0)
262 ret = setenv ("DYLD_FORCE_FLAT_NAMESPACE", "y", 1);
263 #endif
264
265 if (ret != 0)
266 error (EXIT_CANCELED, errno,
267 _("failed to update the environment with %s"),
268 quote (LD_PRELOAD));
269 }
270
271 /* Populate environ with _STDBUF_I=$MODE _STDBUF_O=$MODE _STDBUF_E=$MODE.
272 Return TRUE if any environment variables set. */
273
274 static bool
275 set_libstdbuf_options (void)
276 {
277 bool env_set = false;
278
279 for (size_t i = 0; i < ARRAY_CARDINALITY (stdbuf); i++)
280 {
281 if (stdbuf[i].optarg)
282 {
283 char *var;
284 int ret;
285
286 if (*stdbuf[i].optarg == 'L')
287 ret = asprintf (&var, "%s%c=L", "_STDBUF_",
288 toupper (stdbuf[i].optc));
289 else
290 ret = asprintf (&var, "%s%c=%" PRIuMAX, "_STDBUF_",
291 toupper (stdbuf[i].optc),
292 (uintmax_t) stdbuf[i].size);
293 if (ret < 0)
294 xalloc_die ();
295
296 if (putenv (var) != 0)
297 error (EXIT_CANCELED, errno,
298 _("failed to update the environment with %s"),
299 quote (var));
300
301 env_set = true;
302 }
303 }
304
305 return env_set;
306 }
307
308 int
309 main (int argc, char **argv)
310 {
311 int c;
312
313 initialize_main (&argc, &argv);
314 set_program_name (argv[0]);
315 setlocale (LC_ALL, "");
316 bindtextdomain (PACKAGE, LOCALEDIR);
317 textdomain (PACKAGE);
318
319 initialize_exit_failure (EXIT_CANCELED);
320 atexit (close_stdout);
321
322 while ((c = getopt_long (argc, argv, "+i:o:e:", longopts, nullptr)) != -1)
323 {
324 int opt_fileno;
325
326 switch (c)
327 {
328 /* Old McDonald had a farm ei... */
329 case 'e':
330 case 'i':
331 case 'o':
332 opt_fileno = optc_to_fileno (c);
333 affirm (0 <= opt_fileno && opt_fileno < ARRAY_CARDINALITY (stdbuf));
334 stdbuf[opt_fileno].optc = c;
335 while (c_isspace (*optarg))
336 optarg++;
337 stdbuf[opt_fileno].optarg = optarg;
338 if (c == 'i' && *optarg == 'L')
339 {
340 /* -oL will be by far the most common use of this utility,
341 but one could easily think -iL might have the same affect,
342 so disallow it as it could be confusing. */
343 error (0, 0, _("line buffering stdin is meaningless"));
344 usage (EXIT_CANCELED);
345 }
346
347 if (!STREQ (optarg, "L")
348 && parse_size (optarg, &stdbuf[opt_fileno].size) == -1)
349 error (EXIT_CANCELED, errno, _("invalid mode %s"), quote (optarg));
350
351 break;
352
353 case_GETOPT_HELP_CHAR;
354
355 case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
356
357 default:
358 usage (EXIT_CANCELED);
359 }
360 }
361
362 argv += optind;
363 argc -= optind;
364
365 /* must specify at least 1 command. */
366 if (argc < 1)
367 {
368 error (0, 0, _("missing operand"));
369 usage (EXIT_CANCELED);
370 }
371
372 if (! set_libstdbuf_options ())
373 {
374 error (0, 0, _("you must specify a buffering mode option"));
375 usage (EXIT_CANCELED);
376 }
377
378 /* Try to preload libstdbuf first from the same path as
379 stdbuf is running from. */
380 set_program_path (program_name);
381 if (!program_path)
382 program_path = xstrdup (PKGLIBDIR); /* Need to init to non-null. */
383 set_LD_PRELOAD ();
384 free (program_path);
385
386 execvp (*argv, argv);
387
388 int exit_status = errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE;
389 error (0, errno, _("failed to run command %s"), quote (argv[0]));
390 return exit_status;
391 }