#include <stdio.h>
#include <string.h>

#define MAXLINE 1000 /* maximum input line length */

int grep(char *pattern);

/* somewhat optimized book version of grep */
/* find all lines matching pattern */
int main(int argc, char *argv[])
{
    /* verify arg is given */
    if (argc < 2) {
        printf("error: excpected pattern\n");
        return -1;
    }

    char *pattern = argv[1];

    /* verify pattern */
    char c;
    int i;
    for (i = 0; (c = pattern[i]) != '\0'; i++)
        if (c == '\n') {
            printf("error: newline in pattern\n");
            return -2;
        }

    int found = grep(pattern);
    printf("found = %d\n", found);
    return found;
}

int getln(char line[], int lim);
int strindex(char source[], char searchfor[], int slen);

/* grep: prints lines containing pattern, returns number of matching lines */
int grep(char *pattern)
{
    char line[MAXLINE];
    int found = 0;
    int slen = strlen(pattern);

    while (getln(line, MAXLINE) > 0)
        if (strindex(line, pattern, slen) >= 0) {
            printf("%s", line);
            found++;
        }
    return found;
}

/* getline: get line (including \n) into s, return length */
int getln(char *s, int lim)
{
    int c, i = 0;
   
    while (--lim > 0 && (c = getchar()) != EOF && (s[i++] = c) != '\n')
        ;
    s[i] = '\0';
    return i;
}

/* strindex: return index of t in s, -1 if none */
int strindex(char s[], char t[], int slen)
{
    int i, j;

    for (i = j = 0; s[i]; i++)
        if (s[i] != t[j])
            j = 0;
        else if (++j == slen) { // found match
            return i - slen + 1;
        }
    return -1;
}