fag.c

   1 /* forkaftergrep (C) 2017 Tobias Girstmair, GPLv3 */
   2 //TODO: `tee': bad file descriptor
   3
   4 #define _XOPEN_SOURCE 500
   5 #define _DEFAULT_SOURCE
   6 #include <errno.h>
   7 #include <fcntl.h>
   8 #include <signal.h>
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sysexits.h>
  13 #include <sys/time.h>
  14 #include <sys/wait.h>
  15 #include <unistd.h>
  16 #include "fag.h"
  17
  18 int main (int argc, char** argv) {
  19         struct opt opts = {0, 0, 0, NULL, NULL, STDOUT_FILENO, "-q"};
  20         /* `-q': don't print anything; exit with 0 on match; with 1 on error. used to interface with `grep' */
  21         int opt;
  22         opterr = 0;
  23
  24         /* generate grep options string */
  25         char* p = opts.grepopt+2; /* move cursor behind `q' */
  26
  27         signal (SIGPIPE, SIG_IGN); /* ignore broken pipe between fag and grep */
  28
  29
  30         /* the `+' forces getopt to stop at the first non-option */
  31         while ((opt = getopt (argc, argv, "+t:k::eVhvEFGPiwxyU")) != -1) {
  32                 switch (opt) {
  33                 case 't':
  34                         opts.timeout = atoi (optarg);
  35                         break;
  36                 case 'k':
  37                         opts.kill_sig = optarg ? atoi (optarg) : SIGTERM;
  38                         break;
  39                 case 'e':
  40                         opts.stream = STDERR_FILENO;
  41                         break;
  42                 case 'V':
  43                         opts.verbose = 1;
  44                         break;
  45                 case 'h':
  46                         fprintf (stderr, VERTEXT USAGE
  47                                 "Options:\n"
  48                                 "\t-t N\ttimeout after N seconds\n"
  49                                 "\t-k[M]\tsend signal M to child after timeout (default: 15/SIGTERM)\n"
  50                                 "\t-e\tgrep on stderr instead of stdout\n"
  51                                 "\t-V\tbe verbose; print PROGRAM's stdout/stderr to stderr\n"
  52                                 "\t-[EFP]\tgrep: matcher selection\n"
  53                                 "\t-[iwxU]\tgrep: matching control\n", argv[0]);
  54                         return EX_OK;
  55                 case 'v':
  56                         fprintf (stderr, VERTEXT);
  57                         return EX_OK;
  58                 /* `grep' options (Note: missing `-e:', `-f:') */
  59                 case 'E': case 'F': case 'G': case 'P':
  60                 case 'i': case 'y': case 'w': case 'x':
  61                 case 'U': *(p++)=opt; break;
  62
  63                 default:
  64                         fprintf (stderr, "Unrecognized option: %c\n" USAGE, optopt, argv[0]);
  65                         return EX_USAGE;
  66                 }
  67         }
  68         *p = '\0'; /* terminate grep_options string */
  69
  70         /* the first non-option argument is the search string */
  71         if (optind < argc) {
  72                 opts.pattern = argv[optind++];
  73         } else {
  74                 fprintf (stderr, USAGE "(Missing PATTERN)\n", argv[0]);
  75                 return EX_USAGE;
  76         }
  77
  78         /* the remaining are the program to be run */
  79         if (optind < argc) {
  80                 opts.argv = &(argv[optind]);
  81         } else {
  82                 fprintf (stderr, USAGE "(Missing PROGRAM)\n", argv[0]);
  83                 return EX_USAGE;
  84         }
  85
  86         int retval = fork_after_grep (opts);
  87
  88         return retval;
  89 }
  90
  91 int fork_after_grep (struct opt opts) {
  92         int pipefd[2];
  93         pid_t cpid;
  94         int status;
  95
  96         char buf[BUF_SIZE];
  97         int nbytes;
  98
  99         struct timeval begin, now, diff;
 100
 101         if (pipe(pipefd) == -1) {
 102                 fprintf (stderr, "pipe error (userprog)\n");
 103                 return EX_OSERR;
 104         }
 105
 106         if ((cpid = fork()) == -1) {
 107                 fprintf (stderr, "fork error (userprog): %s", strerror (errno));
 108                 close (pipefd[0]);
 109                 close (pipefd[1]);
 110                 return EX_OSERR;
 111         }
 112
 113         if (cpid == 0) {
 114                 close (pipefd[0]);
 115                 dup2 (pipefd[1], opts.stream);
 116                 close (pipefd[1]);
 117                 //dup2 (open("/dev/null", O_WRONLY), opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 118                 close (opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 119
 120                 if (setsid () == -1) {
 121                         fprintf (stderr, "setsid error (userprog): %s", strerror (errno));
 122                         _exit (EX_OSERR);
 123                 }
 124
 125                 execvp (opts.argv[0], opts.argv);
 126                 fprintf (stderr, "exec error (userprog): %s", strerror (errno));
 127                 _exit (EX_UNAVAILABLE);
 128         } else {
 129                 pid_t grep_cpid;
 130                 int grep_pipefd[2];
 131                 int grep_status;
 132
 133                 close (pipefd[1]);
 134                 fcntl (pipefd[0], F_SETFL, fcntl (pipefd[0], F_GETFL, 0) | O_NONBLOCK);
 135
 136                 gettimeofday (&begin, NULL); /* for timeout */
 137
 138                 if (pipe(grep_pipefd) == -1) {
 139                         fprintf (stderr, "pipe error (grep)\n");
 140                         close (pipefd[0]);
 141                         return EX_OSERR;
 142                 }
 143
 144                 if ((grep_cpid = fork()) == -1) {
 145                         fprintf (stderr, "fork error (grep): %s", strerror (errno));
 146                         close (pipefd[0]);
 147                         close (grep_pipefd[0]);
 148                         close (grep_pipefd[1]);
 149                         return EX_OSERR;
 150                 }
 151
 152                 if (grep_cpid == 0) {
 153                         close (grep_pipefd[1]);
 154                         dup2 (grep_pipefd[0], STDIN_FILENO);
 155                         close (grep_pipefd[0]);
 156
 157                         close (STDERR_FILENO);
 158                         close (STDOUT_FILENO);
 159
 160                         execlp ("grep", "grep", opts.grepopt, opts.pattern, NULL);
 161                         fprintf (stderr, "exec error (grep): %s", strerror (errno));
 162                         _exit (EX_SOFTWARE);
 163                 } else {
 164                         close (grep_pipefd[0]);
 165                         for (;;) {
 166                                 usleep (20000);
 167                                 nbytes = read (pipefd[0], buf, BUF_SIZE);
 168                                 if (nbytes == -1) {
 169                                         switch (errno) {
 170                                         case EAGAIN:
 171                                                 break;
 172                                         default:
 173                                                 fprintf (stderr, "read error (userprog): %s", strerror (errno));
 174                                                 close (pipefd[0]);
 175                                                 close (grep_pipefd[1]);
 176                                                 kill (grep_cpid, SIGTERM);
 177                                                 return EX_IOERR;
 178                                         }
 179                                 } else if (nbytes == 0) {
 180                                         fprintf (stderr, "Child program exited prematurely (userprog).\n");
 181                                         close (pipefd[0]);
 182                                         close (grep_pipefd[1]);
 183                                         kill (grep_cpid, SIGTERM);
 184                                         if (waitpid (cpid, &status, WNOHANG) > 0 && WIFEXITED (status)) {
 185                                                 return WEXITSTATUS (status);
 186                                         }
 187                                         return EX_UNAVAILABLE;
 188                                 } else {
 189                                         /* have new userprog-data, send it to grep */
 190                                         if (opts.verbose) {
 191                                                 write(STDERR_FILENO, buf, nbytes);
 192                                         }
 193
 194                                         write(grep_pipefd[1], buf, nbytes); /* can cause SIGPIPE if grep exited, therefore signal will be ignored */
 195                                 }
 196
 197                                 if (waitpid (grep_cpid, &grep_status, WNOHANG) > 0 && WIFEXITED (grep_status)) {
 198                                         close (grep_pipefd[1]);
 199
 200                                         if (WEXITSTATUS(grep_status) == 0) {
 201                                                 /* grep exited with match found */
 202                                                 printf ("%d\n", cpid);
 203
 204                                                 /* create a new child to keep pipe alive (will exit with exec'd program) */
 205                                                 if (!fork ()) {
 206                                                         int devnull = open("/dev/null", O_WRONLY);
 207                                                         dup2 (devnull, pipefd[0]);
 208                                                         close  (devnull);
 209                                                         while (kill(cpid, 0) != -1 && errno != ESRCH ) sleep (1);
 210                                                         close (pipefd[0]);
 211                                                         _exit(0);
 212                                                 }
 213                                                 close (pipefd[0]);
 214                                                 return EX_OK;
 215                                         } else {
 216                                                 /* grep exited due to an error */
 217                                                 fprintf (stderr, "grep exited due to an error.\n");
 218                                                 close (pipefd[0]);
 219                                                 close (grep_pipefd[1]);
 220                                                 return EX_IOERR;
 221                                         }
 222                                 }
 223
 224                                 if (opts.timeout > 0) {
 225                                         gettimeofday (&now, NULL);
 226                                         timersub (&now, &begin, &diff);
 227                                         if (diff.tv_sec >= opts.timeout) {
 228                                                 fprintf (stderr, "Timeout reached. \n");
 229                                                 if (opts.kill_sig > 0) kill (cpid, opts.kill_sig);
 230                                                 close (pipefd[0]);
 231                                                 close (grep_pipefd[1]);
 232                                                 kill (grep_cpid, SIGTERM);
 233                                                 return EX_UNAVAILABLE;
 234                                         }
 235                                 }
 236                         }
 237                 }
 238         }
 239 }