fag.c

   1 /* forkaftergrep (C) 2017 Tobias Girstmair, GPLv3 */
   2 //TODO: if grep exits with an error, fag thinks a match was found (e.g. grep -BEP, killall grep)
   3 //TODO: allow redirect of both streams to files
   4 //TODO: grep is missing `-e' and `-f' options
   5
   6 #define _XOPEN_SOURCE 500
   7 #define _DEFAULT_SOURCE
   8 #include <errno.h>
   9 #include <fcntl.h>
  10 #include <signal.h>
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <sysexits.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         (void)s; /* squash -Werror=unused-parameter */
  24         if (cpid != 0) kill (cpid, SIGTERM);
  25         exit(1);
  26 }
  27
  28 int main (int argc, char** argv) {
  29         struct opt opts = {0, 0, 0, NULL, NULL, STDOUT_FILENO, "-q"};
  30         /* `-q': don't print anything; exit with 0 on match; with 1 on error. used to interface with `grep' */
  31         int opt;
  32         opterr = 0;
  33
  34         /* generate grep options string */
  35         char* p = opts.grepopt+2; /* move cursor behind `q' */
  36
  37         signal (SIGPIPE, SIG_IGN); /* ignore broken pipe between fag and grep */
  38         struct sigaction sa = {0}; /* terminate child if fag gets interrupted/terminated */
  39         sa.sa_handler = &term_child; /* NOTE: will also be inherited by keep-pipe-alive-child */
  40         sigaction (SIGINT, &sa, NULL);
  41         sigaction (SIGTERM, &sa, NULL);
  42
  43
  44         /* the `+' forces getopt to stop at the first non-option */
  45         while ((opt = getopt (argc, argv, "+t:k::er:VhvEFGPiwxyU")) != -1) {
  46                 switch (opt) {
  47                 case 't':
  48                         opts.timeout = atoi (optarg);
  49                         break;
  50                 case 'k':
  51                         opts.kill_sig = optarg ? atoi (optarg) : SIGTERM;
  52                         break;
  53                 case 'e':
  54                         opts.stream = STDERR_FILENO;
  55                         break;
  56                 case 'V':
  57                         opts.verbose = 1;
  58                         break;
  59                 case 'h':
  60                         fprintf (stderr, VERTEXT USAGE
  61                                 "Options:\n"
  62                                 "\t-t N\ttimeout after N seconds\n"
  63                                 "\t-k[M]\tsend signal M to child after timeout (default: 15/SIGTERM)\n"
  64                                 "\t-e\tgrep on stderr instead of stdout\n"
  65                                 "\t-V\tbe verbose; print PROGRAM's stdout/stderr to stderr\n"
  66                                 "\t-[EFP]\tgrep: matcher selection\n"
  67                                 "\t-[iwxU]\tgrep: matching control\n", argv[0]);
  68                         return EX_OK;
  69                 case 'v':
  70                         fprintf (stderr, VERTEXT);
  71                         return EX_OK;
  72                 /* `grep' options (Note: missing `-e:', `-f:') */
  73                 case 'E': case 'F': case 'G': case 'P':
  74                 case 'i': case 'y': case 'w': case 'x':
  75                 case 'U': *(p++)=opt; break;
  76
  77                 default:
  78                         fprintf (stderr, "Unrecognized option: %c\n" USAGE, optopt, argv[0]);
  79                         return EX_USAGE;
  80                 }
  81         }
  82         *p = '\0'; /* terminate grep_options string */
  83
  84         /* the first non-option argument is the search string */
  85         if (optind < argc) {
  86                 opts.pattern = argv[optind++];
  87         } else {
  88                 fprintf (stderr, USAGE "(Missing PATTERN)\n", argv[0]);
  89                 return EX_USAGE;
  90         }
  91
  92         /* the remaining are the program to be run */
  93         if (optind < argc) {
  94                 opts.argv = &(argv[optind]);
  95         } else {
  96                 fprintf (stderr, USAGE "(Missing PROGRAM)\n", argv[0]);
  97                 return EX_USAGE;
  98         }
  99
 100         int retval = fork_after_grep (opts);
 101
 102         return retval;
 103 }
 104
 105 int fork_after_grep (struct opt opts) {
 106         int pipefd[2];
 107         //pid_t cpid;
 108         int status;
 109
 110         char buf[BUF_SIZE];
 111         int nbytes;
 112
 113         struct timeval begin, now, diff;
 114
 115         if (pipe(pipefd) == -1) {
 116                 fprintf (stderr, "pipe error (userprog)\n");
 117                 return EX_OSERR;
 118         }
 119
 120         if ((cpid = fork()) == -1) {
 121                 fprintf (stderr, "fork error (userprog): %s", strerror (errno));
 122                 close (pipefd[0]);
 123                 close (pipefd[1]);
 124                 return EX_OSERR;
 125         }
 126
 127         if (cpid == 0) {
 128                 close (pipefd[0]);
 129                 dup2 (pipefd[1], opts.stream);
 130                 close (pipefd[1]);
 131                 //dup2 (open("/dev/null", O_WRONLY), opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 132                 close (opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 133
 134                 if (setsid () == -1) {
 135                         fprintf (stderr, "setsid error (userprog): %s", strerror (errno));
 136                         _exit (EX_OSERR);
 137                 }
 138
 139                 execvp (opts.argv[0], opts.argv);
 140                 fprintf (stderr, "exec error (userprog): %s", strerror (errno));
 141                 _exit (EX_UNAVAILABLE);
 142         } else {
 143                 pid_t grep_cpid;
 144                 int grep_pipefd[2];
 145                 int grep_status;
 146
 147                 close (pipefd[1]);
 148                 fcntl (pipefd[0], F_SETFL, fcntl (pipefd[0], F_GETFL, 0) | O_NONBLOCK);
 149
 150                 gettimeofday (&begin, NULL); /* for timeout */
 151
 152                 if (pipe(grep_pipefd) == -1) {
 153                         fprintf (stderr, "pipe error (grep)\n");
 154                         close (pipefd[0]);
 155                         return EX_OSERR;
 156                 }
 157
 158                 if ((grep_cpid = fork()) == -1) {
 159                         fprintf (stderr, "fork error (grep): %s", strerror (errno));
 160                         close (pipefd[0]);
 161                         close (grep_pipefd[0]);
 162                         close (grep_pipefd[1]);
 163                         return EX_OSERR;
 164                 }
 165
 166                 if (grep_cpid == 0) {
 167                         close (grep_pipefd[1]);
 168                         dup2 (grep_pipefd[0], STDIN_FILENO);
 169                         close (grep_pipefd[0]);
 170
 171                         close (STDOUT_FILENO);
 172
 173                         execlp ("grep", "grep", opts.grepopt, "--", opts.pattern, NULL);
 174                         fprintf (stderr, "exec error (grep): %s", strerror (errno));
 175                         _exit (EX_SOFTWARE);
 176                 } else {
 177                         close (grep_pipefd[0]);
 178                         for (;;) {
 179                                 usleep (20000);
 180                                 nbytes = read (pipefd[0], buf, BUF_SIZE);
 181                                 if (nbytes == -1) {
 182                                         switch (errno) {
 183                                         case EAGAIN:
 184                                                 break;
 185                                         default:
 186                                                 fprintf (stderr, "read error (userprog): %s", strerror (errno));
 187                                                 close (pipefd[0]);
 188                                                 close (grep_pipefd[1]);
 189                                                 kill (grep_cpid, SIGTERM);
 190                                                 return EX_IOERR;
 191                                         }
 192                                 } else if (nbytes == 0) {
 193                                         fprintf (stderr, "Child program exited prematurely (userprog).\n");
 194                                         close (pipefd[0]);
 195                                         close (grep_pipefd[1]);
 196                                         kill (grep_cpid, SIGTERM);
 197                                         if (waitpid (cpid, &status, WNOHANG) > 0 && WIFEXITED (status)) {
 198                                                 return WEXITSTATUS (status);
 199                                         }
 200                                         return EX_UNAVAILABLE;
 201                                 } else {
 202                                         /* have new userprog-data, send it to grep */
 203                                         if (opts.verbose) {
 204                                                 write(STDERR_FILENO, buf, nbytes);
 205                                         }
 206
 207                                         write(grep_pipefd[1], buf, nbytes); /* can cause SIGPIPE if grep exited, therefore signal will be ignored */
 208                                 }
 209
 210                                 if (waitpid (grep_cpid, &grep_status, WNOHANG) > 0 && WIFEXITED (grep_status)) {
 211                                         close (grep_pipefd[1]);
 212
 213                                         if (WEXITSTATUS(grep_status) == 0) {
 214                                                 /* grep exited with match found */
 215                                                 printf ("%d\n", cpid);
 216
 217                                                 /* create a new child to keep pipe alive (will exit with exec'd program) */
 218                                                 if (!fork ()) {
 219                                                         int devnull = open("/dev/null", O_WRONLY);
 220                                                         dup2 (devnull, pipefd[0]);
 221                                                         close  (devnull);
 222                                                         while (kill(cpid, 0) != -1 && errno != ESRCH ) sleep (1);
 223                                                         close (pipefd[0]);
 224                                                         _exit(0);
 225                                                 }
 226                                                 close (pipefd[0]);
 227                                                 return EX_OK;
 228                                         } else {
 229                                                 /* grep exited due to an error */
 230                                                 fprintf (stderr, "grep exited due to an error.\n");
 231                                                 close (pipefd[0]);
 232                                                 close (grep_pipefd[1]);
 233                                                 return EX_IOERR;
 234                                         }
 235                                 }
 236
 237                                 if (opts.timeout > 0) {
 238                                         gettimeofday (&now, NULL);
 239                                         timersub (&now, &begin, &diff);
 240                                         if (diff.tv_sec >= opts.timeout) {
 241                                                 fprintf (stderr, "Timeout reached. \n");
 242                                                 if (opts.kill_sig > 0) kill (cpid, opts.kill_sig);
 243                                                 close (pipefd[0]);
 244                                                 close (grep_pipefd[1]);
 245                                                 kill (grep_cpid, SIGTERM);
 246                                                 return EX_UNAVAILABLE;
 247                                         }
 248                                 }
 249                         }
 250                 }
 251         }
 252 }