Word Search

I am getting a run time error (This program has performed an illegal action and will be shut down) I have narrowed it down to the approximate area where fread is called to get the contents of a file and begin the search for a word.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 200

static int cmp( char *a, char *b, int len);
static char *search( char *text, char *word, int len);

int main(int argc, char *argv[])
{
int i,x=1;
char *buf,*found;
FILE *fd;

if (argc<2)
{
     printf("Usage: WORD <file> <word>\n");
     return 1;
}

strcat(argv[1], ".txt");
if ((fd=fopen(argv[1], "r+")) == NULL)
{
     printf("File execution failure\n");
     return 1;
}

while ( (fread(buf, sizeof(char),MAX ,fd )) != 0)
{
	while ( (found = search(buf, argv[2], strlen(argv[2]))) != NULL)
		printf("%d)     %s",x++,*found);
}

printf("\n\nDone\n");
fclose(fd);
return 0;
}

static int cmp( char *a, char *b, int len)
{
	for (; *a == *b; a++, b++)
	{
		if (--len==0)
			return 0;
	}
	return 1;
}

static char *search( char *text, char *word, int len)
{
	for (; *text != '\0'; text++)
	{
		if ( cmp(word,text,len) == 0)
			return text;
	}
	return NULL;
}

> if (argc<2)

This should be:

Code:

if(argc < 3)
{
     printf("Usage: %s <file> <word>\n", argv[0]);
     return 1;
}

argv[0] = <progam name>
argv[1] = <file>
argv[2] = <word>
argc = 3

> strcat(argv[1], ".txt");

I'm not sure this is a good idea. Maybe you should copy argv[1] to another buffer:

Code:

char buf[BUFSIZ];
sprintf(buf, "%s.txt", argv[1]);

Another thing: if you use fread, your buffer will not be null terminated!!! Use fgets or add the null character yourself.

>>fread(buf, sizeof(char),MAX ,fd )
You kinda forgot to tell buf to point to something valid, reading to a pointer to garbage memory is an access violation. Program go boom :-)