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

FILE *fp=NULL;
int main(int argc, char ** argv){
    char line[100];
    int n=100;
    regex_t reg[100];
    regex_t *preg=reg;
    size_t nmatch=0;
    regmatch_t *pmatch;
    if (argc<3) {
	fprintf(stderr,"%s <fname> <regexp>\n", argv[0]);
	fprintf(stderr,"This program searches for the regual expressions in th text file. It prints the line if the regular expression is found, otherwise not. Similar to grep!\n"
	exit(0);
    }
    fp=fopen(argv[1],"r");
    if (!fp) {
	fprintf(stderr,"Cannot open %s.", argv[1]);
	exit(0);
    }

    regcomp(preg, (const char *) argv[2], REG_EXTENDED | REG_NOSUB );
    while (!feof(fp)){
	fgets(line,n,fp);
	if ( regexec(preg, line ,nmatch , pmatch, REG_NOTBOL)!=REG_NOMATCH){
	    fprintf(stderr,"%s",line);
	}
    }
    if (fp) fclose(fp);
    regfree(preg);
    return 0;
}