grep

gistfile1.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <regex.h>
#define _GNU_SOURCE
#include <getopt.h>


static void do_grep(regex_t *pattern, FILE *src, int invert);

static struct option longopts[] = {
  { "ignore-case", no_argument, NULL, 'i'},
  { "invert-match", no_argument, NULL, 'v'},
  { 0, 0, 0, 0 }
};


int main(int argc, char const *argv[])
{

  int opt;
  int reg_flags = REG_EXTENDED | REG_NOSUB | REG_NEWLINE;
  int invert = 0;

  while ((opt = getopt_long(argc, argv, "iv", longopts, NULL)) != -1) {
    switch (opt) {
      case 'i':
        reg_flags |= REG_ICASE;
        break;
      case 'v':
        invert = 1;
        break;
      case '?':
        fprintf(stderr, "Usage: %s [-i] [-v] [pattern] [src]\n", argv[0]);
        exit(1);
    }
  }

  if (optind == argc) {
    fprintf(stderr, "pattern must be specified.");
    exit(1);
  }

  regex_t pattern;
  int err = regcomp(&pattern, argv[optind], reg_flags);
  if (err != 0) {
    char buf[1024];
    regerror(err, &pattern, buf, sizeof buf);
    puts(buf);
    exit(1);
  }

  if (index == argc) {
    do_grep(&pattern, stdin, invert);
  } else {
    int i;
    for (i = ++optind; i < argc; i++) {
      FILE *src = fopen(argv[i], "r");
      if (!src) {
        perror(argv[i]);
        exit(1);
      }
      do_grep(&pattern, src, invert);
      fclose(src);
    }
  }

  regfree(&pattern);
  exit(0);


}

static void do_grep(regex_t *pattern, FILE *src, int invert)
{
  
  char buf[4096];
  while (fgets(buf, sizeof buf, src)) {
    if (regexec(pattern, buf, 0, NULL, 0) == 0 && invert < 1) {
      fputs(buf, stdout);   
    } else {
      if (invert > 0) {
        fputs(buf, stdout);
      }
    }
  }

}