src/bin/lttng/commands/snapshot.c

   1 /*
   2  * Copyright (C) 2013 - David Goulet <dgoulet@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License, version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along with
  14  * this program; if not, write to the Free Software Foundation, Inc., 51
  15  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <assert.h>
  20 #include <inttypes.h>
  21 #include <popt.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26 #include <sys/types.h>
  27 #include <unistd.h>
  28 #include <assert.h>
  29
  30 #include <common/utils.h>
  31 #include <common/mi-lttng.h>
  32 #include <lttng/snapshot.h>
  33
  34 #include "../command.h"
  35
  36 static const char *opt_session_name;
  37 static const char *opt_output_name;
  38 static const char *opt_data_url;
  39 static const char *opt_ctrl_url;
  40 static const char *current_session_name;
  41 static uint64_t opt_max_size;
  42
  43 /* Stub for the cmd struct actions. */
  44 static int cmd_add_output(int argc, const char **argv);
  45 static int cmd_del_output(int argc, const char **argv);
  46 static int cmd_list_output(int argc, const char **argv);
  47 static int cmd_record(int argc, const char **argv);
  48
  49 static const char *indent4 = "    ";
  50
  51 enum {
  52         OPT_HELP = 1,
  53         OPT_LIST_OPTIONS,
  54         OPT_MAX_SIZE,
  55         OPT_LIST_COMMANDS,
  56 };
  57
  58 static struct mi_writer *writer;
  59
  60 static struct poptOption snapshot_opts[] = {
  61         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  62         {"help",      'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
  63         {"session",      's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
  64         {"ctrl-url",     'C', POPT_ARG_STRING, &opt_ctrl_url, 0, 0, 0},
  65         {"data-url",     'D', POPT_ARG_STRING, &opt_data_url, 0, 0, 0},
  66         {"name",         'n', POPT_ARG_STRING, &opt_output_name, 0, 0, 0},
  67         {"max-size",     'm', POPT_ARG_STRING, 0, OPT_MAX_SIZE, 0, 0},
  68         {"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  69         {"list-commands",  0, POPT_ARG_NONE, NULL, OPT_LIST_COMMANDS},
  70         {0, 0, 0, 0, 0, 0, 0}
  71 };
  72
  73 static struct cmd_struct actions[] = {
  74         { "add-output", cmd_add_output },
  75         { "del-output", cmd_del_output },
  76         { "list-output", cmd_list_output },
  77         { "record", cmd_record },
  78         { NULL, NULL }  /* Array closure */
  79 };
  80
  81 /*
  82  * usage
  83  */
  84 static void usage(FILE *ofp)
  85 {
  86         fprintf(ofp, "usage: lttng snapshot [OPTION] ACTION\n");
  87         fprintf(ofp, "\n");
  88         fprintf(ofp, "Actions:\n");
  89         fprintf(ofp, "   add-output [-m <SIZE>] [-s <NAME>] [-n <NAME>] <URL> | -C <URL> -D <URL>\n");
  90         fprintf(ofp, "      Setup and add an snapshot output for a session.\n");
  91         fprintf(ofp, "\n");
  92         fprintf(ofp, "   del-output ID | NAME [-s <NAME>]\n");
  93         fprintf(ofp, "      Delete an output for a session using the ID.\n");
  94         fprintf(ofp, "\n");
  95         fprintf(ofp, "   list-output [-s <NAME>]\n");
  96         fprintf(ofp, "      List the output of a session.\n");
  97         fprintf(ofp, "\n");
  98         fprintf(ofp, "   record [-m <SIZE>] [-s <NAME>] [-n <NAME>] [<URL> | -C <URL> -D <URL>]\n");
  99         fprintf(ofp, "      Snapshot a session's buffer(s) for all domains. If an URL is\n");
 100         fprintf(ofp, "      specified, it is used instead of a previously added output.\n");
 101         fprintf(ofp, "      Specifying only a name or/a size will override the current output value.\n");
 102         fprintf(ofp, "      For instance, you can record a snapshot with a custom maximum size\n");
 103         fprintf(ofp, "      or with a different name.\n");
 104         fprintf(ofp, "\n");
 105         fprintf(ofp, "Options:\n");
 106         fprintf(ofp, "  -h, --help           Show this help\n");
 107         fprintf(ofp, "      --list-options   Simple listing of options\n");
 108         fprintf(ofp, "  -s, --session NAME   Apply to session name\n");
 109         fprintf(ofp, "  -n, --name NAME      Name of the output or snapshot\n");
 110         fprintf(ofp, "  -m, --max-size SIZE  Maximum bytes size of the snapshot {+k,+M,+G}\n");
 111         fprintf(ofp, "  -C, --ctrl-url URL   Set control path URL. (Must use -D also)\n");
 112         fprintf(ofp, "  -D, --data-url URL   Set data path URL. (Must use -C also)\n");
 113         fprintf(ofp, "\n");
 114 }
 115
 116 /*
 117  * Count and return the number of arguments in argv.
 118  */
 119 static int count_arguments(const char **argv)
 120 {
 121         int i = 0;
 122
 123         assert(argv);
 124
 125         while (argv[i] != NULL) {
 126                 i++;
 127         }
 128
 129         return i;
 130 }
 131
 132 /*
 133  * Create a snapshot output object from arguments using the given URL.
 134  *
 135  * Return a newly allocated object or NULL on error.
 136  */
 137 static struct lttng_snapshot_output *create_output_from_args(const char *url)
 138 {
 139         int ret = 0;
 140         struct lttng_snapshot_output *output = NULL;
 141
 142         output = lttng_snapshot_output_create();
 143         if (!output) {
 144                 goto error_create;
 145         }
 146
 147         if (url) {
 148                 ret = lttng_snapshot_output_set_ctrl_url(url, output);
 149                 if (ret < 0) {
 150                         goto error;
 151                 }
 152         } else if (opt_ctrl_url) {
 153                 ret = lttng_snapshot_output_set_ctrl_url(opt_ctrl_url, output);
 154                 if (ret < 0) {
 155                         goto error;
 156                 }
 157         }
 158
 159         if (opt_data_url) {
 160                 ret = lttng_snapshot_output_set_data_url(opt_data_url, output);
 161                 if (ret < 0) {
 162                         goto error;
 163                 }
 164         }
 165
 166         if (opt_max_size) {
 167                 ret = lttng_snapshot_output_set_size(opt_max_size, output);
 168                 if (ret < 0) {
 169                         goto error;
 170                 }
 171         }
 172
 173         if (opt_output_name) {
 174                 ret = lttng_snapshot_output_set_name(opt_output_name, output);
 175                 if (ret < 0) {
 176                         goto error;
 177                 }
 178         }
 179
 180         return output;
 181
 182 error:
 183         lttng_snapshot_output_destroy(output);
 184 error_create:
 185         return NULL;
 186 }
 187
 188 static int mi_list_output(void)
 189 {
 190         int ret;
 191         struct lttng_snapshot_output *s_iter;
 192         struct lttng_snapshot_output_list *list;
 193
 194         assert(writer);
 195
 196         ret = lttng_snapshot_list_output(current_session_name, &list);
 197         if (ret < 0) {
 198                 goto error;
 199         }
 200
 201         ret = mi_lttng_snapshot_output_session_name(writer, current_session_name);
 202         if (ret) {
 203                 ret = CMD_ERROR;
 204                 goto end;
 205         }
 206
 207         while ((s_iter = lttng_snapshot_output_list_get_next(list)) != NULL) {
 208                 ret = mi_lttng_snapshot_list_output(writer, s_iter);
 209                 if (ret) {
 210                         ret = CMD_ERROR;
 211                         goto end;
 212                 }
 213         }
 214
 215
 216         /* Close snapshot snapshots element */
 217         ret = mi_lttng_writer_close_element(writer);
 218         if (ret) {
 219                 ret = CMD_ERROR;
 220                 goto end;
 221         }
 222
 223         /* Close snapshot session element */
 224         ret = mi_lttng_writer_close_element(writer);
 225         if (ret) {
 226                 ret = CMD_ERROR;
 227         }
 228 end:
 229         lttng_snapshot_output_list_destroy(list);
 230 error:
 231         return ret;
 232 }
 233
 234 static int list_output(void)
 235 {
 236         int ret, output_seen = 0;
 237         struct lttng_snapshot_output *s_iter;
 238         struct lttng_snapshot_output_list *list;
 239
 240         ret = lttng_snapshot_list_output(current_session_name, &list);
 241         if (ret < 0) {
 242                 goto error;
 243         }
 244
 245         MSG("Snapshot output list for session %s", current_session_name);
 246
 247         while ((s_iter = lttng_snapshot_output_list_get_next(list)) != NULL) {
 248                 MSG("%s[%" PRIu32 "] %s: %s (max-size: %" PRId64 ")", indent4,
 249                                 lttng_snapshot_output_get_id(s_iter),
 250                                 lttng_snapshot_output_get_name(s_iter),
 251                                 lttng_snapshot_output_get_ctrl_url(s_iter),
 252                                 lttng_snapshot_output_get_maxsize(s_iter));
 253                 output_seen = 1;
 254         }
 255
 256         lttng_snapshot_output_list_destroy(list);
 257
 258         if (!output_seen) {
 259                 MSG("%sNone", indent4);
 260         }
 261
 262 error:
 263         return ret;
 264 }
 265
 266 /*
 267  * Delete output by ID (machine interface version).
 268  */
 269 static int mi_del_output(uint32_t id, const char *name)
 270 {
 271         int ret;
 272         struct lttng_snapshot_output *output = NULL;
 273
 274         assert(writer);
 275
 276         output = lttng_snapshot_output_create();
 277         if (!output) {
 278                 ret = CMD_FATAL;
 279                 goto error;
 280         }
 281
 282         if (name) {
 283                 ret = lttng_snapshot_output_set_name(name, output);
 284         } else if (id != UINT32_MAX) {
 285                 ret = lttng_snapshot_output_set_id(id, output);
 286         } else {
 287                 ret = CMD_ERROR;
 288                 goto error;
 289         }
 290         if (ret < 0) {
 291                 ret = CMD_FATAL;
 292                 goto error;
 293         }
 294
 295         ret = lttng_snapshot_del_output(current_session_name, output);
 296         if (ret < 0) {
 297                 goto error;
 298         }
 299
 300         ret = mi_lttng_snapshot_del_output(writer, id, name, current_session_name);
 301         if (ret) {
 302                 ret = CMD_ERROR;
 303         }
 304
 305 error:
 306         lttng_snapshot_output_destroy(output);
 307         return ret;
 308 }
 309
 310 /*
 311  * Delete output by ID.
 312  */
 313 static int del_output(uint32_t id, const char *name)
 314 {
 315         int ret;
 316         struct lttng_snapshot_output *output = NULL;
 317
 318         output = lttng_snapshot_output_create();
 319         if (!output) {
 320                 ret = CMD_FATAL;
 321                 goto error;
 322         }
 323
 324         if (name) {
 325                 ret = lttng_snapshot_output_set_name(name, output);
 326         } else if (id != UINT32_MAX) {
 327                 ret = lttng_snapshot_output_set_id(id, output);
 328         } else {
 329                 ret = CMD_ERROR;
 330                 goto error;
 331         }
 332         if (ret < 0) {
 333                 ret = CMD_FATAL;
 334                 goto error;
 335         }
 336
 337         ret = lttng_snapshot_del_output(current_session_name, output);
 338         if (ret < 0) {
 339                 goto error;
 340         }
 341
 342         if (id != UINT32_MAX) {
 343                 MSG("Snapshot output id %" PRIu32 " successfully deleted for session %s",
 344                                 id, current_session_name);
 345         } else {
 346                 MSG("Snapshot output %s successfully deleted for session %s",
 347                                 name, current_session_name);
 348         }
 349
 350 error:
 351         lttng_snapshot_output_destroy(output);
 352         return ret;
 353 }
 354
 355 /*
 356  * Add output from the user URL (machine interface).
 357  */
 358 static int mi_add_output(const char *url)
 359 {
 360         int ret;
 361         struct lttng_snapshot_output *output = NULL;
 362         char name[NAME_MAX];
 363         const char *n_ptr;
 364
 365         if (!url && (!opt_data_url || !opt_ctrl_url)) {
 366                 ret = CMD_ERROR;
 367                 goto error;
 368         }
 369
 370         output = create_output_from_args(url);
 371         if (!output) {
 372                 ret = CMD_FATAL;
 373                 goto error;
 374         }
 375
 376         /* This call, if successful, populates the id of the output object. */
 377         ret = lttng_snapshot_add_output(current_session_name, output);
 378         if (ret < 0) {
 379                 goto error;
 380         }
 381
 382         n_ptr = lttng_snapshot_output_get_name(output);
 383         if (*n_ptr == '\0') {
 384                 int pret;
 385                 pret = snprintf(name, sizeof(name), DEFAULT_SNAPSHOT_NAME "-%" PRIu32,
 386                                 lttng_snapshot_output_get_id(output));
 387                 if (pret < 0) {
 388                         PERROR("snprintf add output name");
 389                 }
 390                 n_ptr = name;
 391         }
 392
 393         ret = mi_lttng_snapshot_add_output(writer, current_session_name, n_ptr,
 394                         output);
 395         if (ret) {
 396                 ret = CMD_ERROR;
 397         }
 398
 399 error:
 400         lttng_snapshot_output_destroy(output);
 401         return ret;
 402 }
 403
 404 /*
 405  * Add output from the user URL.
 406  */
 407 static int add_output(const char *url)
 408 {
 409         int ret;
 410         struct lttng_snapshot_output *output = NULL;
 411         char name[NAME_MAX];
 412         const char *n_ptr;
 413
 414         if (!url && (!opt_data_url || !opt_ctrl_url)) {
 415                 ret = CMD_ERROR;
 416                 goto error;
 417         }
 418
 419         output = create_output_from_args(url);
 420         if (!output) {
 421                 ret = CMD_FATAL;
 422                 goto error;
 423         }
 424
 425         /* This call, if successful, populates the id of the output object. */
 426         ret = lttng_snapshot_add_output(current_session_name, output);
 427         if (ret < 0) {
 428                 goto error;
 429         }
 430
 431         n_ptr = lttng_snapshot_output_get_name(output);
 432         if (*n_ptr == '\0') {
 433                 int pret;
 434                 pret = snprintf(name, sizeof(name), DEFAULT_SNAPSHOT_NAME "-%" PRIu32,
 435                                 lttng_snapshot_output_get_id(output));
 436                 if (pret < 0) {
 437                         PERROR("snprintf add output name");
 438                 }
 439                 n_ptr = name;
 440         }
 441
 442         MSG("Snapshot output successfully added for session %s",
 443                         current_session_name);
 444         MSG("  [%" PRIu32 "] %s: %s (max-size: %" PRId64 ")",
 445                         lttng_snapshot_output_get_id(output), n_ptr,
 446                         lttng_snapshot_output_get_ctrl_url(output),
 447                         lttng_snapshot_output_get_maxsize(output));
 448 error:
 449         lttng_snapshot_output_destroy(output);
 450         return ret;
 451 }
 452
 453 static int cmd_add_output(int argc, const char **argv)
 454 {
 455         int ret;
 456
 457         if (argc < 2 && (!opt_data_url || !opt_ctrl_url)) {
 458                 usage(stderr);
 459                 ret = CMD_ERROR;
 460                 goto end;
 461         }
 462
 463         if (lttng_opt_mi) {
 464                 ret = mi_add_output(argv[1]);
 465         } else {
 466                 ret = add_output(argv[1]);
 467         }
 468
 469 end:
 470         return ret;
 471 }
 472
 473 static int cmd_del_output(int argc, const char **argv)
 474 {
 475         int ret;
 476         char *name;
 477         long id;
 478
 479         if (argc < 2) {
 480                 usage(stderr);
 481                 ret = CMD_ERROR;
 482                 goto end;
 483         }
 484
 485         errno = 0;
 486         id = strtol(argv[1], &name, 10);
 487         if (id == 0 && errno == 0) {
 488                 if (lttng_opt_mi) {
 489                         ret = mi_del_output(UINT32_MAX, name);
 490                 } else {
 491                         ret = del_output(UINT32_MAX, name);
 492                 }
 493         } else if (errno == 0 && *name == '\0') {
 494                 if (lttng_opt_mi) {
 495                         ret = mi_del_output(id, NULL);
 496                 } else {
 497                         ret = del_output(id, NULL);
 498                 }
 499         } else {
 500                 ERR("Argument %s not recognized", argv[1]);
 501                 ret = -1;
 502                 goto end;
 503         }
 504
 505 end:
 506         return ret;
 507 }
 508
 509 static int cmd_list_output(int argc, const char **argv)
 510 {
 511         int ret;
 512
 513         if (lttng_opt_mi) {
 514                 ret = mi_list_output();
 515         } else {
 516                 ret = list_output();
 517         }
 518
 519         return ret;
 520 }
 521
 522 /*
 523  * Do a snapshot record with the URL if one is given (machine interface).
 524  */
 525 static int mi_record(const char *url)
 526 {
 527         int ret;
 528         struct lttng_snapshot_output *output = NULL;
 529
 530         output = create_output_from_args(url);
 531         if (!output) {
 532                 ret = CMD_FATAL;
 533                 goto error;
 534         }
 535
 536         ret = lttng_snapshot_record(current_session_name, output, 0);
 537         if (ret < 0) {
 538                 ret = CMD_ERROR;
 539                 goto error;
 540         }
 541
 542         ret = mi_lttng_snapshot_record(writer, current_session_name, url,
 543                         opt_ctrl_url, opt_data_url);
 544         if (ret) {
 545                 ret = CMD_ERROR;
 546         }
 547
 548 error:
 549         lttng_snapshot_output_destroy(output);
 550         return ret;
 551 }
 552
 553 /*
 554  * Do a snapshot record with the URL if one is given.
 555  */
 556 static int record(const char *url)
 557 {
 558         int ret;
 559         struct lttng_snapshot_output *output = NULL;
 560
 561         output = create_output_from_args(url);
 562         if (!output) {
 563                 ret = CMD_FATAL;
 564                 goto error;
 565         }
 566
 567         ret = lttng_snapshot_record(current_session_name, output, 0);
 568         if (ret < 0) {
 569                 if (ret == -LTTNG_ERR_MAX_SIZE_INVALID) {
 570                         ERR("The minimum size of a snapshot is computed by multiplying "
 571                                         "the total amount of streams with the largest subbuffer "
 572                                         "in the session.");
 573                 }
 574                 goto error;
 575         }
 576
 577         MSG("Snapshot recorded successfully for session %s", current_session_name);
 578
 579         if (url) {
 580                 MSG("Snapshot written at: %s", url);
 581         } else if (opt_ctrl_url) {
 582                 MSG("Snapshot written to ctrl: %s, data: %s", opt_ctrl_url,
 583                                 opt_data_url);
 584         }
 585
 586 error:
 587         lttng_snapshot_output_destroy(output);
 588         return ret;
 589 }
 590
 591 static int cmd_record(int argc, const char **argv)
 592 {
 593         int ret;
 594
 595         if (argc == 2) {
 596                 /* With a given URL */
 597                 if (lttng_opt_mi) {
 598                         ret = mi_record(argv[1]);
 599                 } else {
 600                         ret = record(argv[1]);
 601                 }
 602         } else {
 603                 if (lttng_opt_mi) {
 604                         ret = mi_record(NULL);
 605                 } else {
 606                         ret = record(NULL);
 607                 }
 608         }
 609
 610         return ret;
 611 }
 612
 613 static int handle_command(const char **argv)
 614 {
 615         int ret = CMD_SUCCESS, i = 0, argc, command_ret =  CMD_SUCCESS;
 616         struct cmd_struct *cmd;
 617
 618         if (argv == NULL || (!opt_ctrl_url && opt_data_url) ||
 619                         (opt_ctrl_url && !opt_data_url)) {
 620                 usage(stderr);
 621                 command_ret = CMD_ERROR;
 622                 goto end;
 623         }
 624
 625         argc = count_arguments(argv);
 626
 627         cmd = &actions[i];
 628         while (cmd->func != NULL) {
 629                 /* Find command */
 630                 if (strcmp(argv[0], cmd->name) == 0) {
 631                         if (lttng_opt_mi) {
 632                                 /* Action element */
 633                                 ret = mi_lttng_writer_open_element(writer,
 634                                                 mi_lttng_element_command_action);
 635                                 if (ret) {
 636                                         ret = CMD_ERROR;
 637                                         goto end;
 638                                 }
 639
 640                                 /* Name of the action */
 641                                 ret = mi_lttng_writer_write_element_string(writer,
 642                                                 config_element_name, argv[0]);
 643                                 if (ret) {
 644                                         ret = CMD_ERROR;
 645                                         goto end;
 646                                 }
 647
 648                                 /* Open output element */
 649                                 ret = mi_lttng_writer_open_element(writer,
 650                                                 mi_lttng_element_command_output);
 651                                 if (ret) {
 652                                         ret = CMD_ERROR;
 653                                         goto end;
 654                                 }
 655                         }
 656
 657                         command_ret = cmd->func(argc, argv);
 658
 659                         if (lttng_opt_mi) {
 660                                 /* Close output and action element */
 661                                 ret = mi_lttng_close_multi_element(writer, 2);
 662                                 if (ret) {
 663                                         ret = CMD_ERROR;
 664                                         goto end;
 665                                 }
 666                         }
 667                         goto end;
 668                 }
 669                 i++;
 670                 cmd = &actions[i];
 671         }
 672
 673         ret = CMD_UNDEFINED;
 674
 675 end:
 676         /* Overwrite ret if an error occurred in cmd->func() */
 677         ret = command_ret ? command_ret : ret;
 678         return ret;
 679 }
 680 /*
 681  * The 'snapshot <cmd> <options>' first level command
 682  */
 683 int cmd_snapshot(int argc, const char **argv)
 684 {
 685         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 686         char *session_name = NULL;
 687         static poptContext pc;
 688
 689         pc = poptGetContext(NULL, argc, argv, snapshot_opts, 0);
 690         poptReadDefaultConfig(pc, 0);
 691
 692         /* Mi check */
 693         if (lttng_opt_mi) {
 694                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 695                 if (!writer) {
 696                         ret = -LTTNG_ERR_NOMEM;
 697                         goto end;
 698                 }
 699
 700                 /* Open command element */
 701                 ret = mi_lttng_writer_command_open(writer,
 702                                 mi_lttng_element_command_snapshot);
 703                 if (ret) {
 704                         ret = CMD_ERROR;
 705                         goto end;
 706                 }
 707
 708                 /* Open output element */
 709                 ret = mi_lttng_writer_open_element(writer,
 710                                 mi_lttng_element_command_output);
 711                 if (ret) {
 712                         ret = CMD_ERROR;
 713                         goto end;
 714                 }
 715         }
 716
 717         while ((opt = poptGetNextOpt(pc)) != -1) {
 718                 switch (opt) {
 719                 case OPT_HELP:
 720                         usage(stdout);
 721                         goto end;
 722                 case OPT_LIST_OPTIONS:
 723                         list_cmd_options(stdout, snapshot_opts);
 724                         goto end;
 725                 case OPT_LIST_COMMANDS:
 726                         list_commands(actions, stdout);
 727                         goto end;
 728                 case OPT_MAX_SIZE:
 729                 {
 730                         uint64_t val;
 731                         const char *opt = poptGetOptArg(pc);
 732
 733                         if (utils_parse_size_suffix((char *) opt, &val) < 0) {
 734                                 ERR("Unable to handle max-size value %s", opt);
 735                                 ret = CMD_ERROR;
 736                                 goto end;
 737                         }
 738
 739                         opt_max_size = val;
 740
 741                         break;
 742                 }
 743                 default:
 744                         usage(stderr);
 745                         ret = CMD_UNDEFINED;
 746                         goto end;
 747                 }
 748         }
 749
 750         if (!opt_session_name) {
 751                 session_name = get_session_name();
 752                 if (session_name == NULL) {
 753                         ret = CMD_ERROR;
 754                         goto end;
 755                 }
 756                 current_session_name = session_name;
 757         } else {
 758                 current_session_name = opt_session_name;
 759         }
 760
 761         command_ret = handle_command(poptGetArgs(pc));
 762         if (command_ret) {
 763                 switch (-command_ret) {
 764                 case LTTNG_ERR_EPERM:
 765                         ERR("The session needs to be set in no output mode (--no-output)");
 766                         break;
 767                 case LTTNG_ERR_SNAPSHOT_NODATA:
 768                         WARN("%s", lttng_strerror(command_ret));
 769                         break;
 770                 default:
 771                         ERR("%s", lttng_strerror(command_ret));
 772                         break;
 773                 }
 774                 success = 0;
 775         }
 776
 777         if (lttng_opt_mi) {
 778                 /* Close output element */
 779                 ret = mi_lttng_writer_close_element(writer);
 780                 if (ret) {
 781                         ret = CMD_ERROR;
 782                         goto end;
 783                 }
 784
 785                 /* Success ? */
 786                 ret = mi_lttng_writer_write_element_bool(writer,
 787                                 mi_lttng_element_command_success, success);
 788                 if (ret) {
 789                         ret = CMD_ERROR;
 790                         goto end;
 791                 }
 792
 793                 /* Command element close */
 794                 ret = mi_lttng_writer_command_close(writer);
 795                 if (ret) {
 796                         ret = CMD_ERROR;
 797                         goto end;
 798                 }
 799         }
 800
 801 end:
 802         /* Mi clean-up */
 803         if (writer && mi_lttng_writer_destroy(writer)) {
 804                 /* Preserve original error code */
 805                 ret = ret ? ret : -LTTNG_ERR_MI_IO_FAIL;
 806         }
 807
 808         if (!opt_session_name) {
 809                 free(session_name);
 810         }
 811
 812         /* Overwrite ret if an error occured during handle_command */
 813         ret = command_ret ? command_ret : ret;
 814         poptFreeContext(pc);
 815         return ret;
 816 }