misc/nstat.c

   1 /*
   2  * nstat.c      handy utility to read counters /proc/net/netstat and snmp
   3  *
   4  *              This program is free software; you can redistribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License, or (at your option) any later version.
   8  *
   9  * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  10  */
  11
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <unistd.h>
  15 #include <fcntl.h>
  16 #include <string.h>
  17 #include <errno.h>
  18 #include <time.h>
  19 #include <sys/time.h>
  20 #include <fnmatch.h>
  21 #include <sys/file.h>
  22 #include <sys/socket.h>
  23 #include <sys/un.h>
  24 #include <sys/poll.h>
  25 #include <sys/wait.h>
  26 #include <sys/stat.h>
  27 #include <signal.h>
  28 #include <math.h>
  29 #include <getopt.h>
  30
  31 #include <json_writer.h>
  32 #include <SNAPSHOT.h>
  33 #include "utils.h"
  34
  35 int dump_zeros;
  36 int reset_history;
  37 int ignore_history;
  38 int no_output;
  39 int json_output;
  40 int no_update;
  41 int scan_interval;
  42 int time_constant;
  43 double W;
  44 char **patterns;
  45 int npatterns;
  46
  47 char info_source[128];
  48 int source_mismatch;
  49
  50 static int generic_proc_open(const char *env, char *name)
  51 {
  52         char store[128];
  53         char *p = getenv(env);
  54
  55         if (!p) {
  56                 p = getenv("PROC_ROOT") ? : "/proc";
  57                 snprintf(store, sizeof(store)-1, "%s/%s", p, name);
  58                 p = store;
  59         }
  60         return open(p, O_RDONLY);
  61 }
  62
  63 static int net_netstat_open(void)
  64 {
  65         return generic_proc_open("PROC_NET_NETSTAT", "net/netstat");
  66 }
  67
  68 static int net_snmp_open(void)
  69 {
  70         return generic_proc_open("PROC_NET_SNMP", "net/snmp");
  71 }
  72
  73 static int net_snmp6_open(void)
  74 {
  75         return generic_proc_open("PROC_NET_SNMP6", "net/snmp6");
  76 }
  77
  78 static int net_sctp_snmp_open(void)
  79 {
  80         return generic_proc_open("PROC_NET_SCTP_SNMP", "net/sctp/snmp");
  81 }
  82
  83 struct nstat_ent {
  84         struct nstat_ent *next;
  85         char             *id;
  86         unsigned long long val;
  87         double             rate;
  88 };
  89
  90 struct nstat_ent *kern_db;
  91 struct nstat_ent *hist_db;
  92
  93 static const char *useless_numbers[] = {
  94         "IpForwarding", "IpDefaultTTL",
  95         "TcpRtoAlgorithm", "TcpRtoMin", "TcpRtoMax",
  96         "TcpMaxConn", "TcpCurrEstab"
  97 };
  98
  99 static int useless_number(const char *id)
 100 {
 101         int i;
 102
 103         for (i = 0; i < ARRAY_SIZE(useless_numbers); i++)
 104                 if (strcmp(id, useless_numbers[i]) == 0)
 105                         return 1;
 106         return 0;
 107 }
 108
 109 static int match(const char *id)
 110 {
 111         int i;
 112
 113         if (npatterns == 0)
 114                 return 1;
 115
 116         for (i = 0; i < npatterns; i++) {
 117                 if (!fnmatch(patterns[i], id, FNM_CASEFOLD))
 118                         return 1;
 119         }
 120         return 0;
 121 }
 122
 123 static void load_good_table(FILE *fp)
 124 {
 125         char buf[4096];
 126         struct nstat_ent *db = NULL;
 127         struct nstat_ent *n;
 128
 129         while (fgets(buf, sizeof(buf), fp) != NULL) {
 130                 int nr;
 131                 unsigned long long val;
 132                 double rate;
 133                 char idbuf[sizeof(buf)];
 134
 135                 if (buf[0] == '#') {
 136                         buf[strlen(buf)-1] = 0;
 137                         if (info_source[0] && strcmp(info_source, buf+1))
 138                                 source_mismatch = 1;
 139                         info_source[0] = 0;
 140                         strncat(info_source, buf+1, sizeof(info_source)-1);
 141                         continue;
 142                 }
 143                 /* idbuf is as big as buf, so this is safe */
 144                 nr = sscanf(buf, "%s%llu%lg", idbuf, &val, &rate);
 145                 if (nr < 2) {
 146                         fprintf(stderr, "%s:%d: error parsing history file\n",
 147                                 __FILE__, __LINE__);
 148                         exit(-2);
 149                 }
 150                 if (nr < 3)
 151                         rate = 0;
 152                 if (useless_number(idbuf))
 153                         continue;
 154                 if ((n = malloc(sizeof(*n))) == NULL) {
 155                         perror("nstat: malloc");
 156                         exit(-1);
 157                 }
 158                 n->id = strdup(idbuf);
 159                 n->val = val;
 160                 n->rate = rate;
 161                 n->next = db;
 162                 db = n;
 163         }
 164
 165         while (db) {
 166                 n = db;
 167                 db = db->next;
 168                 n->next = kern_db;
 169                 kern_db = n;
 170         }
 171 }
 172
 173 static int count_spaces(const char *line)
 174 {
 175         int count = 0;
 176         char c;
 177
 178         while ((c = *line++) != 0)
 179                 count += c == ' ' || c == '\n';
 180         return count;
 181 }
 182
 183 static void load_ugly_table(FILE *fp)
 184 {
 185         char *buf = NULL;
 186         size_t buflen = 0;
 187         ssize_t nread;
 188         struct nstat_ent *db = NULL;
 189         struct nstat_ent *n;
 190
 191         while ((nread = getline(&buf, &buflen, fp)) != -1) {
 192                 char idbuf[4096];
 193                 int  off;
 194                 char *p;
 195                 int count1, count2, skip = 0;
 196
 197                 p = strchr(buf, ':');
 198                 if (!p) {
 199                         fprintf(stderr, "%s:%d: error parsing history file\n",
 200                                 __FILE__, __LINE__);
 201                         exit(-2);
 202                 }
 203                 count1 = count_spaces(buf);
 204                 *p = 0;
 205                 idbuf[0] = 0;
 206                 strncat(idbuf, buf, sizeof(idbuf) - 1);
 207                 off = p - buf;
 208                 p += 2;
 209
 210                 while (*p) {
 211                         char *next;
 212
 213                         if ((next = strchr(p, ' ')) != NULL)
 214                                 *next++ = 0;
 215                         else if ((next = strchr(p, '\n')) != NULL)
 216                                 *next++ = 0;
 217                         if (off < sizeof(idbuf)) {
 218                                 idbuf[off] = 0;
 219                                 strncat(idbuf, p, sizeof(idbuf) - off - 1);
 220                         }
 221                         n = malloc(sizeof(*n));
 222                         if (!n) {
 223                                 perror("nstat: malloc");
 224                                 exit(-1);
 225                         }
 226                         n->id = strdup(idbuf);
 227                         n->rate = 0;
 228                         n->next = db;
 229                         db = n;
 230                         p = next;
 231                 }
 232                 n = db;
 233                 nread = getline(&buf, &buflen, fp);
 234                 if (nread == -1) {
 235                         fprintf(stderr, "%s:%d: error parsing history file\n",
 236                                 __FILE__, __LINE__);
 237                         exit(-2);
 238                 }
 239                 count2 = count_spaces(buf);
 240                 if (count2 > count1)
 241                         skip = count2 - count1;
 242                 do {
 243                         p = strrchr(buf, ' ');
 244                         if (!p) {
 245                                 fprintf(stderr, "%s:%d: error parsing history file\n",
 246                                         __FILE__, __LINE__);
 247                                 exit(-2);
 248                         }
 249                         *p = 0;
 250                         if (sscanf(p+1, "%llu", &n->val) != 1) {
 251                                 fprintf(stderr, "%s:%d: error parsing history file\n",
 252                                         __FILE__, __LINE__);
 253                                 exit(-2);
 254                         }
 255                         /* Trick to skip "dummy" trailing ICMP MIB in 2.4 */
 256                         if (skip)
 257                                 skip--;
 258                         else
 259                                 n = n->next;
 260                 } while (p > buf + off + 2);
 261         }
 262         free(buf);
 263
 264         while (db) {
 265                 n = db;
 266                 db = db->next;
 267                 if (useless_number(n->id)) {
 268                         free(n->id);
 269                         free(n);
 270                 } else {
 271                         n->next = kern_db;
 272                         kern_db = n;
 273                 }
 274         }
 275 }
 276
 277 static void load_sctp_snmp(void)
 278 {
 279         FILE *fp = fdopen(net_sctp_snmp_open(), "r");
 280
 281         if (fp) {
 282                 load_good_table(fp);
 283                 fclose(fp);
 284         }
 285 }
 286
 287 static void load_snmp(void)
 288 {
 289         FILE *fp = fdopen(net_snmp_open(), "r");
 290
 291         if (fp) {
 292                 load_ugly_table(fp);
 293                 fclose(fp);
 294         }
 295 }
 296
 297 static void load_snmp6(void)
 298 {
 299         FILE *fp = fdopen(net_snmp6_open(), "r");
 300
 301         if (fp) {
 302                 load_good_table(fp);
 303                 fclose(fp);
 304         }
 305 }
 306
 307 static void load_netstat(void)
 308 {
 309         FILE *fp = fdopen(net_netstat_open(), "r");
 310
 311         if (fp) {
 312                 load_ugly_table(fp);
 313                 fclose(fp);
 314         }
 315 }
 316
 317
 318 static void dump_kern_db(FILE *fp, int to_hist)
 319 {
 320         json_writer_t *jw = json_output ? jsonw_new(fp) : NULL;
 321         struct nstat_ent *n, *h;
 322
 323         h = hist_db;
 324         if (jw) {
 325                 jsonw_start_object(jw);
 326                 jsonw_pretty(jw, pretty);
 327                 jsonw_name(jw, info_source);
 328                 jsonw_start_object(jw);
 329         } else
 330                 fprintf(fp, "#%s\n", info_source);
 331
 332         for (n = kern_db; n; n = n->next) {
 333                 unsigned long long val = n->val;
 334
 335                 if (!dump_zeros && !val && !n->rate)
 336                         continue;
 337                 if (!match(n->id)) {
 338                         struct nstat_ent *h1;
 339
 340                         if (!to_hist)
 341                                 continue;
 342                         for (h1 = h; h1; h1 = h1->next) {
 343                                 if (strcmp(h1->id, n->id) == 0) {
 344                                         val = h1->val;
 345                                         h = h1->next;
 346                                         break;
 347                                 }
 348                         }
 349                 }
 350
 351                 if (jw)
 352                         jsonw_uint_field(jw, n->id, val);
 353                 else
 354                         fprintf(fp, "%-32s%-16llu%6.1f\n", n->id, val, n->rate);
 355         }
 356
 357         if (jw) {
 358                 jsonw_end_object(jw);
 359
 360                 jsonw_end_object(jw);
 361                 jsonw_destroy(&jw);
 362         }
 363 }
 364
 365 static void dump_incr_db(FILE *fp)
 366 {
 367         json_writer_t *jw = json_output ? jsonw_new(fp) : NULL;
 368         struct nstat_ent *n, *h;
 369
 370         h = hist_db;
 371         if (jw) {
 372                 jsonw_start_object(jw);
 373                 jsonw_pretty(jw, pretty);
 374                 jsonw_name(jw, info_source);
 375                 jsonw_start_object(jw);
 376         } else
 377                 fprintf(fp, "#%s\n", info_source);
 378
 379         for (n = kern_db; n; n = n->next) {
 380                 int ovfl = 0;
 381                 unsigned long long val = n->val;
 382                 struct nstat_ent *h1;
 383
 384                 for (h1 = h; h1; h1 = h1->next) {
 385                         if (strcmp(h1->id, n->id) == 0) {
 386                                 if (val < h1->val) {
 387                                         ovfl = 1;
 388                                         val = h1->val;
 389                                 }
 390                                 val -= h1->val;
 391                                 h = h1->next;
 392                                 break;
 393                         }
 394                 }
 395                 if (!dump_zeros && !val && !n->rate)
 396                         continue;
 397                 if (!match(n->id))
 398                         continue;
 399
 400                 if (jw)
 401                         jsonw_uint_field(jw, n->id, val);
 402                 else
 403                         fprintf(fp, "%-32s%-16llu%6.1f%s\n", n->id, val,
 404                                 n->rate, ovfl?" (overflow)":"");
 405         }
 406
 407         if (jw) {
 408                 jsonw_end_object(jw);
 409
 410                 jsonw_end_object(jw);
 411                 jsonw_destroy(&jw);
 412         }
 413 }
 414
 415 static int children;
 416
 417 static void sigchild(int signo)
 418 {
 419 }
 420
 421 static void update_db(int interval)
 422 {
 423         struct nstat_ent *n, *h;
 424
 425         n = kern_db;
 426         kern_db = NULL;
 427
 428         load_netstat();
 429         load_snmp6();
 430         load_snmp();
 431         load_sctp_snmp();
 432
 433         h = kern_db;
 434         kern_db = n;
 435
 436         for (n = kern_db; n; n = n->next) {
 437                 struct nstat_ent *h1;
 438
 439                 for (h1 = h; h1; h1 = h1->next) {
 440                         if (strcmp(h1->id, n->id) == 0) {
 441                                 double sample;
 442                                 unsigned long long incr = h1->val - n->val;
 443
 444                                 n->val = h1->val;
 445                                 sample = (double)incr * 1000.0 / interval;
 446                                 if (interval >= scan_interval) {
 447                                         n->rate += W*(sample-n->rate);
 448                                 } else if (interval >= 1000) {
 449                                         if (interval >= time_constant) {
 450                                                 n->rate = sample;
 451                                         } else {
 452                                                 double w = W*(double)interval/scan_interval;
 453
 454                                                 n->rate += w*(sample-n->rate);
 455                                         }
 456                                 }
 457
 458                                 while (h != h1) {
 459                                         struct nstat_ent *tmp = h;
 460
 461                                         h = h->next;
 462                                         free(tmp->id);
 463                                         free(tmp);
 464                                 };
 465                                 h = h1->next;
 466                                 free(h1->id);
 467                                 free(h1);
 468                                 break;
 469                         }
 470                 }
 471         }
 472 }
 473
 474 #define T_DIFF(a, b) (((a).tv_sec-(b).tv_sec)*1000 + ((a).tv_usec-(b).tv_usec)/1000)
 475
 476
 477 static void server_loop(int fd)
 478 {
 479         struct timeval snaptime = { 0 };
 480         struct pollfd p;
 481
 482         p.fd = fd;
 483         p.events = p.revents = POLLIN;
 484
 485         sprintf(info_source, "%d.%lu sampling_interval=%d time_const=%d",
 486                 getpid(), (unsigned long)random(), scan_interval/1000, time_constant/1000);
 487
 488         load_netstat();
 489         load_snmp6();
 490         load_snmp();
 491         load_sctp_snmp();
 492
 493         for (;;) {
 494                 int status;
 495                 time_t tdiff;
 496                 struct timeval now;
 497
 498                 gettimeofday(&now, NULL);
 499                 tdiff = T_DIFF(now, snaptime);
 500                 if (tdiff >= scan_interval) {
 501                         update_db(tdiff);
 502                         snaptime = now;
 503                         tdiff = 0;
 504                 }
 505                 if (poll(&p, 1, scan_interval - tdiff) > 0
 506                     && (p.revents&POLLIN)) {
 507                         int clnt = accept(fd, NULL, NULL);
 508
 509                         if (clnt >= 0) {
 510                                 pid_t pid;
 511
 512                                 if (children >= 5) {
 513                                         close(clnt);
 514                                 } else if ((pid = fork()) != 0) {
 515                                         if (pid > 0)
 516                                                 children++;
 517                                         close(clnt);
 518                                 } else {
 519                                         FILE *fp = fdopen(clnt, "w");
 520
 521                                         if (fp)
 522                                                 dump_kern_db(fp, 0);
 523                                         exit(0);
 524                                 }
 525                         }
 526                 }
 527                 while (children && waitpid(-1, &status, WNOHANG) > 0)
 528                         children--;
 529         }
 530 }
 531
 532 static int verify_forging(int fd)
 533 {
 534         struct ucred cred;
 535         socklen_t olen = sizeof(cred);
 536
 537         if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, (void *)&cred, &olen) ||
 538             olen < sizeof(cred))
 539                 return -1;
 540         if (cred.uid == getuid() || cred.uid == 0)
 541                 return 0;
 542         return -1;
 543 }
 544
 545 static void usage(void) __attribute__((noreturn));
 546
 547 static void usage(void)
 548 {
 549         fprintf(stderr,
 550                 "Usage: nstat [OPTION] [ PATTERN [ PATTERN ] ]\n"
 551                 "   -h, --help          this message\n"
 552                 "   -a, --ignore        ignore history\n"
 553                 "   -d, --scan=SECS     sample every statistics every SECS\n"
 554                 "   -j, --json          format output in JSON\n"
 555                 "   -n, --nooutput      do history only\n"
 556                 "   -p, --pretty        pretty print\n"
 557                 "   -r, --reset         reset history\n"
 558                 "   -s, --noupdate      don't update history\n"
 559                 "   -t, --interval=SECS report average over the last SECS\n"
 560                 "   -V, --version       output version information\n"
 561                 "   -z, --zeros         show entries with zero activity\n");
 562         exit(-1);
 563 }
 564
 565 static const struct option longopts[] = {
 566         { "help", 0, 0, 'h' },
 567         { "ignore",  0,  0, 'a' },
 568         { "scan", 1, 0, 'd'},
 569         { "nooutput", 0, 0, 'n' },
 570         { "json", 0, 0, 'j' },
 571         { "reset", 0, 0, 'r' },
 572         { "noupdate", 0, 0, 's' },
 573         { "pretty", 0, 0, 'p' },
 574         { "interval", 1, 0, 't' },
 575         { "version", 0, 0, 'V' },
 576         { "zeros", 0, 0, 'z' },
 577         { 0 }
 578 };
 579
 580 int main(int argc, char *argv[])
 581 {
 582         char *hist_name;
 583         struct sockaddr_un sun;
 584         FILE *hist_fp = NULL;
 585         int ch;
 586         int fd;
 587
 588         while ((ch = getopt_long(argc, argv, "h?vVzrnasd:t:jp",
 589                                  longopts, NULL)) != EOF) {
 590                 switch (ch) {
 591                 case 'z':
 592                         dump_zeros = 1;
 593                         break;
 594                 case 'r':
 595                         reset_history = 1;
 596                         break;
 597                 case 'a':
 598                         ignore_history = 1;
 599                         break;
 600                 case 's':
 601                         no_update = 1;
 602                         break;
 603                 case 'n':
 604                         no_output = 1;
 605                         break;
 606                 case 'd':
 607                         scan_interval = 1000*atoi(optarg);
 608                         break;
 609                 case 't':
 610                         if (sscanf(optarg, "%d", &time_constant) != 1 ||
 611                             time_constant <= 0) {
 612                                 fprintf(stderr, "nstat: invalid time constant divisor\n");
 613                                 exit(-1);
 614                         }
 615                         break;
 616                 case 'j':
 617                         json_output = 1;
 618                         break;
 619                 case 'p':
 620                         pretty = 1;
 621                         break;
 622                 case 'v':
 623                 case 'V':
 624                         printf("nstat utility, iproute2-ss%s\n", SNAPSHOT);
 625                         exit(0);
 626                 case 'h':
 627                 case '?':
 628                 default:
 629                         usage();
 630                 }
 631         }
 632
 633         argc -= optind;
 634         argv += optind;
 635
 636         sun.sun_family = AF_UNIX;
 637         sun.sun_path[0] = 0;
 638         sprintf(sun.sun_path+1, "nstat%d", getuid());
 639
 640         if (scan_interval > 0) {
 641                 if (time_constant == 0)
 642                         time_constant = 60;
 643                 time_constant *= 1000;
 644                 W = 1 - 1/exp(log(10)*(double)scan_interval/time_constant);
 645                 if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
 646                         perror("nstat: socket");
 647                         exit(-1);
 648                 }
 649                 if (bind(fd, (struct sockaddr *)&sun, 2+1+strlen(sun.sun_path+1)) < 0) {
 650                         perror("nstat: bind");
 651                         exit(-1);
 652                 }
 653                 if (listen(fd, 5) < 0) {
 654                         perror("nstat: listen");
 655                         exit(-1);
 656                 }
 657                 if (daemon(0, 0)) {
 658                         perror("nstat: daemon");
 659                         exit(-1);
 660                 }
 661                 signal(SIGPIPE, SIG_IGN);
 662                 signal(SIGCHLD, sigchild);
 663                 server_loop(fd);
 664                 exit(0);
 665         }
 666
 667         patterns = argv;
 668         npatterns = argc;
 669
 670         if ((hist_name = getenv("NSTAT_HISTORY")) == NULL) {
 671                 hist_name = malloc(128);
 672                 sprintf(hist_name, "/tmp/.nstat.u%d", getuid());
 673         }
 674
 675         if (reset_history)
 676                 unlink(hist_name);
 677
 678         if (!ignore_history || !no_update) {
 679                 struct stat stb;
 680
 681                 fd = open(hist_name, O_RDWR|O_CREAT|O_NOFOLLOW, 0600);
 682                 if (fd < 0) {
 683                         perror("nstat: open history file");
 684                         exit(-1);
 685                 }
 686                 if ((hist_fp = fdopen(fd, "r+")) == NULL) {
 687                         perror("nstat: fdopen history file");
 688                         exit(-1);
 689                 }
 690                 if (flock(fileno(hist_fp), LOCK_EX)) {
 691                         perror("nstat: flock history file");
 692                         exit(-1);
 693                 }
 694                 if (fstat(fileno(hist_fp), &stb) != 0) {
 695                         perror("nstat: fstat history file");
 696                         exit(-1);
 697                 }
 698                 if (stb.st_nlink != 1 || stb.st_uid != getuid()) {
 699                         fprintf(stderr, "nstat: something is so wrong with history file, that I prefer not to proceed.\n");
 700                         exit(-1);
 701                 }
 702                 if (!ignore_history) {
 703                         FILE *tfp;
 704                         long uptime = -1;
 705
 706                         if ((tfp = fopen("/proc/uptime", "r")) != NULL) {
 707                                 if (fscanf(tfp, "%ld", &uptime) != 1)
 708                                         uptime = -1;
 709                                 fclose(tfp);
 710                         }
 711                         if (uptime >= 0 && time(NULL) >= stb.st_mtime+uptime) {
 712                                 fprintf(stderr, "nstat: history is aged out, resetting\n");
 713                                 if (ftruncate(fileno(hist_fp), 0) < 0)
 714                                         perror("nstat: ftruncate");
 715                         }
 716                 }
 717
 718                 load_good_table(hist_fp);
 719
 720                 hist_db = kern_db;
 721                 kern_db = NULL;
 722         }
 723
 724         if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) >= 0 &&
 725             (connect(fd, (struct sockaddr *)&sun, 2+1+strlen(sun.sun_path+1)) == 0
 726              || (strcpy(sun.sun_path+1, "nstat0"),
 727                  connect(fd, (struct sockaddr *)&sun, 2+1+strlen(sun.sun_path+1)) == 0))
 728             && verify_forging(fd) == 0) {
 729                 FILE *sfp = fdopen(fd, "r");
 730
 731                 if (!sfp) {
 732                         fprintf(stderr, "nstat: fdopen failed: %s\n",
 733                                 strerror(errno));
 734                         close(fd);
 735                 } else {
 736                         load_good_table(sfp);
 737                         if (hist_db && source_mismatch) {
 738                                 fprintf(stderr, "nstat: history is stale, ignoring it.\n");
 739                                 hist_db = NULL;
 740                         }
 741                         fclose(sfp);
 742                 }
 743         } else {
 744                 if (fd >= 0)
 745                         close(fd);
 746                 if (hist_db && info_source[0] && strcmp(info_source, "kernel")) {
 747                         fprintf(stderr, "nstat: history is stale, ignoring it.\n");
 748                         hist_db = NULL;
 749                         info_source[0] = 0;
 750                 }
 751                 load_netstat();
 752                 load_snmp6();
 753                 load_snmp();
 754                 load_sctp_snmp();
 755                 if (info_source[0] == 0)
 756                         strcpy(info_source, "kernel");
 757         }
 758
 759         if (!no_output) {
 760                 if (ignore_history || hist_db == NULL)
 761                         dump_kern_db(stdout, 0);
 762                 else
 763                         dump_incr_db(stdout);
 764         }
 765         if (!no_update) {
 766                 if (ftruncate(fileno(hist_fp), 0) < 0)
 767                         perror("nstat: ftruncate");
 768                 rewind(hist_fp);
 769
 770                 json_output = 0;
 771                 dump_kern_db(hist_fp, 1);
 772                 fclose(hist_fp);
 773         }
 774         exit(0);
 775 }