simple grep

grep.c

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <string.h>
#include <unistd.h>
#include <regex.h>

/**
 * Simple grep
 * 
 * see: http://souptonuts.sourceforge.net/code/regexp.c.html
 * see: http://www.gnu.org/s/libc/manual/html_node/Example-of-Getopt.html#Example-of-Getopt
 */

#define NUM_MATCHES 4//max sub-matches

char buffer[1024];
char pom[1024];
char *pattern = NULL;
regex_t preg;
regmatch_t pmatch[NUM_MATCHES];
size_t rm, i;
int mode = 0;
int counter;
int only_numbers = 0;
int reverse = 0;
int show_line_num = 0;
int only_matching = 0;

void parse(FILE * in) {
    int i = 1;
    while (fgets(buffer, 1024, in)) {
        /* it's possible something won't compile like  ./regexp '*' abc */
        if ((rm = regcomp(&preg, pattern, mode)) != 0) {
            fprintf(stderr, "Invalid expression:'%s'\n", pattern);
        }
        if (!reverse ^ (rm = regexec(&preg, buffer, NUM_MATCHES, pmatch, mode))) {
            if (!only_numbers) {
                if (show_line_num)
                    printf("%i:", i);

                if (!only_matching)
                    printf("%s", buffer);
                else { // Print match
                    strncpy(pom, buffer + pmatch[0].rm_so,
                            pmatch[0].rm_eo - pmatch[0].rm_so);
                    pom[pmatch[0].rm_eo - pmatch[0].rm_so] = '\0';
                    printf("%s\n", pom);
                }
            }
            counter++;
        }
        i++;
    }

    if (only_numbers)
        printf("%d\n", counter);

}

int main(int argc, char **argv) {
    int c;
    FILE * file;

    opterr = 0;

    while ((c = getopt(argc, argv, "Eicvno")) != -1) {
        switch (c) {
            case 'E':
                mode |= REG_EXTENDED;
                break;
            case 'i':
                mode |= REG_ICASE;
                break;
            case 'c':
                only_numbers = 1;
                break;
            case 'v':
                reverse = 1;
                break;
            case 'n':
                show_line_num = 1;
                break;
            case 'o':
                only_matching = 1;
                break;
            /*
            case '?':
                if (optopt == 'c')
                    fprintf(stderr, "Option -%c requires an argument.\n", optopt);
                else
             */
                if (isprint(optopt))
                    fprintf(stderr, "Unknown option `-%c'.\n", optopt);
                else
                    fprintf(stderr, "Unknown option character `\\x%x'.\n", optopt);
                return 1;
            default:
                abort();
        }
    }

    if (!argv[optind]) {
        fprintf(stderr, "No pattern given.\n");
        abort();
    } else {
        pattern = argv[optind];
        //printf("pattern: %s\n", pattern);
    }

    if (argv[optind + 1]) {
        //printf("file: %s\n", argv[optind + 1]);
        file = fopen(argv[optind + 1], "r");
        if (!file) {
            fprintf(stderr, "No such file!\n");
            abort();
        }
        parse(file);

    } else {
        parse(stdin);
    }


    return 0;
}