Exercise 7.7 - Pattern matching program with files

Question

Modify the pattern finding program of Chapter 5 to take its input from a set of named files or, if no files are named as arguments, from the standard input. Should the file name be printed when a matching line is found?

/*
 * Modify the pattern finding program of Chapter 5 to take its input from a set of named files or,
 * if no files are named as arguments, from the standard input.
 * Should the file name be printed when a matching line is found?
 */

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

#define MAXLINE 1000

int mgetline(char *line,int max);

char pattern[] = "ould"; /* pattern to search for */

/* find all the matching patterns */

int main(void)
{
    char line[MAXLINE];

    int found=0;

    /* mgetline ends when a newline starts with X */
    while((mgetline(line,MAXLINE)) > 0)
        if(strindex(line,pattern) >= 0) {
            printf("%s\n",line);
            found++;
        }

    return 0;

}

/* mgetline */

int mgetline(char *s,int lim)
{
    int c;
    char *t=s;

    while(--lim > 0 && (c=getchar())!='X' && c!='\n')
        *s++=c;

    if(c=='\n')
        *s++=c;
    *s='\0';

    return s-t;
}

/* strindex */

int strindex(char *s,char *t)
{
    char *b=s;
    char *p,*r;

    for(;*s!='\0';s++)
    {
        for(p=s,r=t;*r!='\0' && *p==*r;p++,r++)
            ;

            if(r>t && *r == '\0')
                return s-b;
    }
    return -1;
}
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