src/stdbuf.c

   1 /* stdbuf -- setup the standard streams for a command
   2    Copyright (C) 2009-2024 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                             c_toupper (stdbuf[i].optc));
 289           else
 290             ret = asprintf (&var, "%s%c=%zu", "_STDBUF_",
 291                             c_toupper (stdbuf[i].optc),
 292                             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 }