fag.c

   1 /* forkaftergrep (C) 2017 Tobias Girstmair, GPLv3 */
   2 //TODO: if grep exits with an error, fag thinks a match was found
   3
   4 #define _XOPEN_SOURCE 500
   5 #define _DEFAULT_SOURCE
   6 #include <errno.h>
   7 #include <fcntl.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <sysexits.h>
  12 #include <sys/time.h>
  13 #include <sys/wait.h>
  14 #include <unistd.h>
  15 #include "fag.h"
  16
  17 int main (int argc, char** argv) {
  18         struct opt opts = {0, 0, 0, NULL, NULL, STDOUT_FILENO};
  19         struct grepopt optg = {basic_regexp, 0, 0, 0, 0};
  20         int opt;
  21         opterr = 0;
  22
  23         /* the `+' forces getopt to stop at the first non-option */
  24         while ((opt = getopt (argc, argv, "+t:k::eVhvEFGPiwxyU")) != -1) {
  25                 switch (opt) {
  26                 case 't':
  27                         opts.timeout = atoi (optarg);
  28                         break;
  29                 case 'k':
  30                         opts.kill_sig = optarg ? atoi (optarg) : SIGTERM;
  31                         break;
  32                 case 'e':
  33                         opts.stream = STDERR_FILENO;
  34                         break;
  35                 case 'V':
  36                         opts.verbose = 1;
  37                         break;
  38                 case 'h':
  39                         fprintf (stderr, VERTEXT USAGE
  40                                 "Options:\n"
  41                                 "\t-t N\ttimeout after N seconds\n"
  42                                 "\t-k [M]\tsend signal M to child after timeout (default: 15/SIGTERM)\n"
  43                                 "\t-e\tgrep on stderr instead of stdout\n"
  44                                 "\t-V\tbe verbose; print PROGRAM's stdout/stderr to stderr\n"
  45                                 "\t-[EFGPiwxyU]\t grep options\n", argv[0]);
  46                         return EX_OK;
  47                 case 'v':
  48                         fprintf (stderr, VERTEXT);
  49                         return EX_OK;
  50                 /* `grep' options (Note: missing `-e:', `-f:') */
  51                 case 'E': optg.regex = extended_regexp; break;
  52                 case 'F': optg.regex = fixed_strings  ; break;
  53                 case 'G': optg.regex = basic_regexp   ; break; /* grep default */
  54                 case 'P': optg.regex = perl_regexp    ; break;
  55                 case 'i': /* fall thru */
  56                 case 'y': optg.ignore_case = 1; break;
  57                 case 'w': optg.word_regexp = 1; break;
  58                 case 'x': optg.line_regexp = 1; break;
  59                 case 'U': optg.binary      = 1; break;
  60
  61                 default:
  62                         fprintf (stderr, "Unrecognized option: %c\n" USAGE, optopt, argv[0]);
  63                         return EX_USAGE;
  64                 }
  65         }
  66
  67         /* the first non-option argument is the search string */
  68         if (optind < argc) {
  69                 opts.pattern = argv[optind++];
  70         } else {
  71                 fprintf (stderr, USAGE "(Missing PATTERN)\n", argv[0]);
  72                 return EX_USAGE;
  73         }
  74
  75         /* the remaining are the program to be run */
  76         if (optind < argc) {
  77                 opts.argv = &(argv[optind]);
  78         } else {
  79                 fprintf (stderr, USAGE "(Missing PROGRAM)\n", argv[0]);
  80                 return EX_USAGE;
  81         }
  82
  83         int retval = fork_after_grep (opts, optg);
  84
  85         return retval;
  86 }
  87
  88 int fork_after_grep (struct opt opts, struct grepopt optg) {
  89         int pipefd[2];
  90         pid_t cpid;
  91         int status;
  92
  93         char buf[BUF_SIZE];
  94         int nbytes;
  95
  96         struct timeval begin, now, diff;
  97
  98         if (pipe(pipefd) == -1) {
  99                 fprintf (stderr, "pipe error (userprog)\n");
 100                 return EX_OSERR;
 101         }
 102
 103         if ((cpid = fork()) == -1) {
 104                 fprintf (stderr, "fork error (userprog): %s", strerror (errno));
 105                 close (pipefd[0]);
 106                 close (pipefd[1]);
 107                 return EX_OSERR;
 108         }
 109
 110         if (cpid == 0) {
 111                 close (pipefd[0]);
 112                 dup2 (pipefd[1], opts.stream);
 113                 close (pipefd[1]);
 114                 close (opts.stream==STDOUT_FILENO?STDERR_FILENO:STDOUT_FILENO);
 115
 116                 if (setsid () == -1) {
 117                         fprintf (stderr, "setsid error (userprog): %s", strerror (errno));
 118                         _exit (EX_OSERR);
 119                 }
 120
 121                 execvp (opts.argv[0], opts.argv);
 122                 fprintf (stderr, "exec error (userprog): %s", strerror (errno));
 123                 _exit (EX_UNAVAILABLE);
 124         } else {
 125                 pid_t grep_cpid;
 126                 int grep_pipefd[2];
 127                 int grep_status;
 128
 129                 close (pipefd[1]);
 130                 fcntl (pipefd[0], F_SETFL, fcntl (pipefd[0], F_GETFL, 0) | O_NONBLOCK);
 131
 132                 gettimeofday (&begin, NULL); /* for timeout */
 133
 134                 if (pipe(grep_pipefd) == -1) {
 135                         fprintf (stderr, "pipe error (grep)\n");
 136                         close (pipefd[0]);
 137                         close (pipefd[1]);
 138                         return EX_OSERR;
 139                 }
 140
 141                 if ((grep_cpid = fork()) == -1) {
 142                         fprintf (stderr, "fork error (grep): %s", strerror (errno));
 143                         close (pipefd[0]);
 144                         close (pipefd[1]);
 145                         close (grep_pipefd[0]);
 146                         close (grep_pipefd[1]);
 147                         return EX_OSERR;
 148                 }
 149
 150                 if (grep_cpid == 0) {
 151                         close (grep_pipefd[1]);
 152                         dup2 (grep_pipefd[0], STDIN_FILENO);
 153                         close (grep_pipefd[0]);
 154
 155                         close (STDERR_FILENO);
 156                         close (STDOUT_FILENO);
 157
 158                         /* generate argument list on the fly (TODO: ugly) */
 159                         /* `-q': don't print anything; exit with 0 on match; with 1 on error */
 160                         char grep_options[16] = "-q";
 161                         char* p = grep_options+2;
 162                         if (optg.regex == extended_regexp) *(p++)='E';
 163                         if (optg.regex == fixed_strings)   *(p++)='F';
 164                         if (optg.regex == basic_regexp)    *(p++)='G';
 165                         if (optg.regex == perl_regexp)     *(p++)='P';
 166                         if (optg.ignore_case)              *(p++)='i';
 167                         if (optg.word_regexp)              *(p++)='w';
 168                         if (optg.line_regexp)              *(p++)='x';
 169                         if (optg.binary)                   *(p++)='U';
 170                         *p = '\0';
 171
 172                         execlp ("grep", "grep", grep_options, opts.pattern, NULL);
 173                         fprintf (stderr, "exec error (grep): %s", strerror (errno));
 174                         _exit (EX_SOFTWARE);
 175                 } else {
 176                         close (grep_pipefd[0]);
 177                         for (;;) {
 178                                 usleep (20000);
 179                                 nbytes = read (pipefd[0], buf, BUF_SIZE);
 180                                 if (nbytes == -1) {
 181                                         switch (errno) {
 182                                         case EAGAIN:
 183                                                 break;
 184                                         default:
 185                                                 fprintf (stderr, "read error (userprog): %s", strerror (errno));
 186                                                 close (pipefd[0]);
 187                                                 close (pipefd[1]);
 188                                                 close (grep_pipefd[1]);
 189                                                 //TODO: kill grep?
 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 (pipefd[1]);
 196                                         close (grep_pipefd[1]);
 197                                         //TODO: kill grep?
 198                                         if (waitpid (cpid, &status, WNOHANG) > 0 && WIFEXITED (status)) {
 199                                                 return WEXITSTATUS (status);
 200                                         }
 201                                         return EX_UNAVAILABLE;
 202                                 } else {
 203                                         /* have new userprog-data, send it to grep */
 204                                         if (opts.verbose) {
 205                                                 write(STDERR_FILENO, buf, nbytes);
 206                                         }
 207
 208                                         write(grep_pipefd[1], buf, nbytes);
 209                                 }
 210
 211                                 // TODO: exits with `0' even if `grep' exits with code > 0 !
 212                                 if (waitpid (grep_cpid, &grep_status, WNOHANG) > 0 && WIFEXITED (grep_status)) {
 213                                         close (grep_pipefd[1]);
 214
 215                                         if (WEXITSTATUS(grep_status) == 0) {
 216                                                 /* grep exited with match found */
 217                                                 printf ("%d\n", cpid);
 218
 219                                                 /* create a new child to keep pipe alive (will exit with exec'd program) */
 220                                                 if (!fork ()) {
 221                                                         while (kill(cpid, 0) != -1 && errno != ESRCH ) sleep (1);
 222                                                         close (pipefd[0]);
 223                                                         close (pipefd[1]);
 224                                                         _exit(0);
 225                                                 }
 226                                                 close (pipefd[0]);
 227                                                 close (pipefd[1]);
 228                                                 return EX_OK;
 229                                         } else {
 230                                                 /* grep exited due to an error */
 231                                                 fprintf (stderr, "grep exited due to an error.");
 232                                                 close (pipefd[0]);
 233                                                 close (pipefd[1]);
 234                                                 close (grep_pipefd[1]);
 235                                                 return EX_IOERR;
 236                                         }
 237                                 }
 238
 239                                 if (opts.timeout > 0) {
 240                                         gettimeofday (&now, NULL);
 241                                         timersub (&now, &begin, &diff);
 242                                         if (diff.tv_sec >= opts.timeout) {
 243                                                 fprintf (stderr, "Timeout reached. \n");
 244                                                 if (opts.kill_sig > 0) kill (cpid, opts.kill_sig);
 245                                                 close (pipefd[0]);
 246                                                 close (pipefd[1]);
 247                                                 close (grep_pipefd[1]);
 248                                                 //TODO: kill grep?
 249                                                 return EX_UNAVAILABLE;
 250                                         }
 251                                 }
 252                         }
 253                 }
 254         }
 255 }