fag.c

   1 /* forkaftergrep (C) 2017 Tobias Girstmair, GPLv3 */
   2 //TODO: allow redirect of both streams to files (have to simulate `tee(1)' in the pipe-passer and the dummy-proc; instead of closing nontracked fd redirect to logfile/devnull)
   3 //TODO: grep is missing `-e' and `-f' options
   4
   5 #define _XOPEN_SOURCE 500
   6 #define _DEFAULT_SOURCE
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <signal.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <sysexits.h>
  14 #include <sys/stat.h>
  15 #include <sys/time.h>
  16 #include <sys/wait.h>
  17 #include <unistd.h>
  18 #include "fag.h"
  19
  20 pid_t cpid = 0;
  21
  22 void term_child(int s) {
  23         if (cpid != 0) kill (cpid, s);
  24         exit(1);
  25 }
  26
  27 int main (int argc, char** argv) {
  28         struct opt opts = {0, 0, 0, NULL, NULL, "/dev/null", "/dev/null", STDOUT_FILENO, "-q"};
  29         /* `-q': don't print anything; exit with 0 on match; with 1 on error. used to interface with `grep' */
  30         int opt;
  31         opterr = 0;
  32
  33         /* generate grep options string */
  34         char* p = opts.grepopt+2; /* move cursor behind `q' */
  35
  36         signal (SIGPIPE, SIG_IGN); /* ignore broken pipe between fag and grep */
  37         struct sigaction sa = {0}; /* terminate child if fag gets interrupted/terminated */
  38         sa.sa_handler = &term_child; /* NOTE: will also be inherited by keep-pipe-alive-child */
  39         sigaction (SIGINT, &sa, NULL);
  40         sigaction (SIGTERM, &sa, NULL);
  41
  42
  43         /* the `+' forces getopt to stop at the first non-option */
  44         while ((opt = getopt (argc, argv, "+t:k::rl:L:VhvEFGPiwxyUZJe:f:")) != -1) {
  45                 switch (opt) {
  46                 case 't':
  47                         opts.timeout = atoi (optarg);
  48                         break;
  49                 case 'k':
  50                         opts.kill_sig = optarg ? atoi (optarg) : SIGTERM;
  51                         break;
  52                 case 'r':
  53                         opts.stream = STDERR_FILENO;
  54                         break;
  55                 case 'l':
  56                         fprintf (stderr, "WARNING: `-l' not currently implemented\n");
  57                         opts.logout = optarg;
  58                         break;
  59                 case 'L':
  60                         fprintf (stderr, "WARNING: `-L' not currently implemented\n");
  61                         opts.logerr = optarg;
  62                         break;
  63                 case 'V':
  64                         opts.verbose = 1;
  65                         break;
  66                 case 'h':
  67                         fprintf (stderr, VERTEXT USAGE
  68                                 "Options:\n"
  69                                 "\t-t N\ttimeout after N seconds\n"
  70                                 "\t-k[N]\tsend signal N to child after timeout (default: 15/SIGTERM)\n"
  71                                 "\t-r\tgrep on stderr instead of stdout\n"
  72                                 "\t-l FILE\tlog PROGRAM's stdout to FILE\n"
  73                                 "\t-L FILE\tlog PROGRAM's stderr to FILE\n"
  74                                 "\t-V\tbe verbose; print monitored stream to stderr\n"
  75                                 "\t-[EFGP]\tgrep: matcher selection\n"
  76                                 "\t-[iwxU]\tgrep: matching control\n"
  77                                 "\t-[ZJ]\tgrep: decompression control\n", argv[0]);
  78                         return EX_OK;
  79                 case 'v':
  80                         fprintf (stderr, VERTEXT);
  81                         return EX_OK;
  82                 case 'e': case 'f':
  83                         fprintf (stderr, "`grep -e' and `-f' are not implemented yet!\n");
  84                         return EX_SOFTWARE;
  85                         break;
  86                 case 'E': case 'F': case 'G': case 'P':
  87                 case 'i': case 'y': case 'w': case 'x':
  88                 case 'U': case 'Z': case 'J':
  89                         *(p++)=opt;
  90                         break;
  91
  92                 default:
  93                         fprintf (stderr, "Unrecognized option: %c\n" USAGE, optopt, argv[0]);
  94                         return EX_USAGE;
  95                 }
  96         }
  97         *p = '\0'; /* terminate grep_options string */
  98
  99         /* the first non-option argument is the search string */
 100         if (optind < argc) {
 101                 opts.pattern = argv[optind++];
 102         } else {
 103                 fprintf (stderr, USAGE "(Missing PATTERN)\n", argv[0]);
 104                 return EX_USAGE;
 105         }
 106
 107         /* the remaining are the program to be run */
 108         if (optind < argc) {
 109                 opts.argv = &(argv[optind]);
 110         } else {
 111                 fprintf (stderr, USAGE "(Missing PROGRAM)\n", argv[0]);
 112                 return EX_USAGE;
 113         }
 114
 115         int retval = fork_after_grep (opts);
 116
 117         return retval;
 118 }
 119
 120 int fork_after_grep (struct opt opts) {
 121         int pipefd[2];
 122         int pipefd_cpid[2]; /* IPC to extract PID from daemonized userprog */
 123         pid_t tmp_cpid;
 124         int status;
 125
 126         char buf[BUF_SIZE];
 127         int nbytes;
 128
 129         struct timeval begin, now, diff;
 130
 131         if (pipe(pipefd) == -1) {
 132                 fprintf (stderr, "pipe error (userprog)\n");
 133                 return EX_OSERR;
 134         }
 135
 136         if(pipe(pipefd_cpid) == -1) {
 137                 fprintf (stderr, "pipe error (cpid-ipc)\n");
 138                 close (pipefd[0]);
 139                 close (pipefd[1]);
 140                 return EX_OSERR;
 141         }
 142
 143         if ((tmp_cpid = fork()) == -1) {
 144                 fprintf (stderr, "fork error (daemonizer): %s", strerror (errno));
 145                 close (pipefd[0]);
 146                 close (pipefd[1]);
 147                 close (pipefd_cpid[0]);
 148                 close (pipefd_cpid[1]);
 149                 return EX_OSERR;
 150         }
 151
 152         if (tmp_cpid == 0) {
 153                 pid_t cpid_userprog;
 154
 155                 close (pipefd[0]);
 156                 dup2 (pipefd[1], opts.stream);
 157                 close (pipefd[1]);
 158                 //dup2 (open("/dev/null", O_WRONLY), opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 159                 close (opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 160
 161                 if (setsid () == -1) {
 162                         fprintf (stderr, "setsid error (daemonizer): %s", strerror (errno));
 163                         _exit (EX_OSERR);
 164                 }
 165
 166                 if ((cpid_userprog = fork()) == -1) {
 167                         fprintf (stderr, "fork error (userprog): %s", strerror (errno));
 168                         _exit (EX_OSERR);
 169                 }
 170                 if (cpid_userprog == 0) {
 171                         close(pipefd_cpid[0]);
 172                         close(pipefd_cpid[1]);
 173
 174                         execvp (opts.argv[0], opts.argv);
 175                         fprintf (stderr, "exec error (userprog): %s", strerror (errno));
 176                 } else {
 177                         /* only way to get final child's pid to main is through IPC */
 178                         write(pipefd_cpid[1], &cpid_userprog, sizeof(pid_t));
 179                         close(pipefd_cpid[0]);
 180                         close(pipefd_cpid[1]);
 181                 }
 182                 _exit (EX_UNAVAILABLE);
 183         } else {
 184                 pid_t grep_cpid;
 185                 int grep_pipefd[2];
 186                 int grep_status;
 187
 188                 /* read userprog's PID from IPC: */
 189                 read(pipefd_cpid[0], &cpid, sizeof(pid_t));
 190                 close(pipefd_cpid[0]);
 191                 close(pipefd_cpid[1]);
 192
 193                 close (pipefd[1]);
 194                 fcntl (pipefd[0], F_SETFL, fcntl (pipefd[0], F_GETFL, 0) | O_NONBLOCK);
 195
 196                 gettimeofday (&begin, NULL); /* for timeout */
 197
 198                 if (pipe(grep_pipefd) == -1) {
 199                         fprintf (stderr, "pipe error (grep)\n");
 200                         close (pipefd[0]);
 201                         return EX_OSERR;
 202                 }
 203
 204                 if ((grep_cpid = fork()) == -1) {
 205                         fprintf (stderr, "fork error (grep): %s", strerror (errno));
 206                         close (pipefd[0]);
 207                         close (grep_pipefd[0]);
 208                         close (grep_pipefd[1]);
 209                         return EX_OSERR;
 210                 }
 211
 212                 if (grep_cpid == 0) {
 213                         close (grep_pipefd[1]);
 214                         dup2 (grep_pipefd[0], STDIN_FILENO);
 215                         close (grep_pipefd[0]);
 216
 217                         close (STDOUT_FILENO);
 218
 219                         execlp ("grep", "grep", opts.grepopt, "--", opts.pattern, NULL);
 220                         fprintf (stderr, "exec error (grep): %s", strerror (errno));
 221                         _exit (EX_SOFTWARE);
 222                 } else {
 223                         close (grep_pipefd[0]);
 224                         for (;;) {
 225                                 usleep (20000);
 226                                 nbytes = read (pipefd[0], buf, BUF_SIZE);
 227                                 if (nbytes == -1) {
 228                                         switch (errno) {
 229                                         case EAGAIN:
 230                                                 break;
 231                                         default:
 232                                                 fprintf (stderr, "read error (userprog): %s", strerror (errno));
 233                                                 close (pipefd[0]);
 234                                                 close (grep_pipefd[1]);
 235                                                 kill (grep_cpid, SIGTERM);
 236                                                 return EX_IOERR;
 237                                         }
 238                                 } else if (nbytes == 0) {
 239                                         fprintf (stderr, "Child program exited prematurely (userprog).\n");
 240                                         close (pipefd[0]);
 241                                         close (grep_pipefd[1]);
 242                                         kill (grep_cpid, SIGTERM);
 243                                         if (waitpid (cpid, &status, WNOHANG) > 0 && WIFEXITED (status)) {
 244                                                 return WEXITSTATUS (status);
 245                                         }
 246                                         return EX_UNAVAILABLE;
 247                                 } else {
 248                                         /* have new userprog-data, send it to grep */
 249                                         if (opts.verbose) {
 250                                                 write(STDERR_FILENO, buf, nbytes);
 251                                         }
 252
 253                                         write(grep_pipefd[1], buf, nbytes); /* can cause SIGPIPE if grep exited, therefore signal will be ignored */
 254                                 }
 255
 256                                 if (waitpid (grep_cpid, &grep_status, WNOHANG) > 0 && WIFEXITED (grep_status)) {
 257                                         close (grep_pipefd[1]);
 258
 259                                         if (WEXITSTATUS(grep_status) == 0) {
 260                                                 /* grep exited with match found */
 261                                                 printf ("%d\n", cpid);
 262                                                 fflush (stdout);
 263
 264                                                 /* create a new child to keep pipe alive, empty it and write log files (will exit with exec'd program) */
 265                                                 if (!fork()){setsid();if(!fork()) {
 266                                                         close(0); close(1); close(2); umask(0); chdir("/");
 267                                                         int devnull = open("/dev/null", O_WRONLY);
 268                                                         dup2 (devnull, pipefd[0]);
 269                                                         close  (devnull);
 270                                                         while (kill(cpid, 0) != -1 && errno != ESRCH ) sleep (1);
 271                                                         close (pipefd[0]);
 272                                                         _exit(0);
 273                                                 }}
 274                                                 close (pipefd[0]);
 275                                                 return EX_OK;
 276                                         } else {
 277                                                 /* grep exited due to an error */
 278                                                 fprintf (stderr, "grep exited due to an error.\n");
 279                                                 close (pipefd[0]);
 280                                                 close (grep_pipefd[1]);
 281                                                 return EX_IOERR;
 282                                         }
 283                                 }
 284
 285                                 if (opts.timeout > 0) {
 286                                         gettimeofday (&now, NULL);
 287                                         timersub (&now, &begin, &diff);
 288                                         if (diff.tv_sec >= opts.timeout) {
 289                                                 fprintf (stderr, "Timeout reached. \n");
 290                                                 if (opts.kill_sig > 0) kill (cpid, opts.kill_sig);
 291                                                 close (pipefd[0]);
 292                                                 close (grep_pipefd[1]);
 293                                                 kill (grep_cpid, SIGTERM);
 294                                                 return EX_UNAVAILABLE;
 295                                         }
 296                                 }
 297                         }
 298                 }
 299         }
 300 }