Word Searching using fgetc - c

Question

I am trying to make word search using fgetc. I understand what fgetc does but i am getting seg fault. on running the gdb test, i returns the following. Is there an easier way to implement the search function?? i am new to programming.
thank you for the help.
#0 0x00007ffff7aa4c64 in getc () from /lib64/libc.so.6
#1 0x000000000040070c in main ()
Where am i going wrong?
#include <stdio.h>
#include <stdlib.h>
int isAlpha(char c)
{
if( c >= 'A' && c <='Z' || c >= 'a' && c <='z' || c >= '0' && c <= '9' )
{
return 1;
}
else
{
return 0;
}
}
int CheckFunctionn(int length, int message_counter, char ref_word[], char newmessage[])
{
int newCounter = 0;
int counterSuccess = 0;
while(newCounter < length)
{
if(ref_word[newCounter] == newmessage[newCounter + message_counter])
{
counterSuccess++;
}
newCounter++;
}
if(counterSuccess == length)
{
return 1;
}
else
{
return 0;
}
}
int main(int argc, char *argv[])
{
char message[300];
int counter = 0;
int ref_length = 0;
int alphaCounter = 0;
int alphaCounterTime = 0;
int messageCounter = 0;
int word_counter = 0;
FILE* input;
FILE* output;
//long fileLength;
//int bufferLength;
//char readFile;
//int forkValue;
input = fopen(argv[2],"r");
output = fopen(argv[3],"w");
int c;
c = fgetc(input);
while(c != EOF)
{
while((argv[1])[ref_length] !='\0')
{
// if string is "HEY", (argv[1]) is HEY, ref_counter is the length
// which in this case will be 3.
ref_length++; //<-- takes care of the length.
}
while(alphaCounter < ref_length)
{
// this will add to alphaCounter everyetime alphaCT is success.
alphaCounterTime += isAlpha((argv[1])[alphaCounter]);
alphaCounter++;
}
if(alphaCounterTime != ref_length)
{
return 0;
}
if((messageCounter == 0 ) && (message[messageCounter + ref_length] == ' ' || message[messageCounter] == '\n' || message[messageCounter]== '\t')) // counts the whole things and brings me to space
{
// compare the message with the word
word_counter += CheckFunctionn(ref_length, messageCounter, argv[1], message);
}
if((message[messageCounter] == ' ' || message[messageCounter] == '\n' || message[messageCounter]== '\t') && (message[messageCounter + ref_length + 1] == ' ' || message[messageCounter + ref_length + 1] == '\n' || message[messageCounter + ref_length + 1]== '\t'))
{
word_counter += CheckFunctionn(ref_length, messageCounter + 1, argv[1], message);
}
if((message[messageCounter]== ' '|| message[messageCounter] == '\n' || message[messageCounter]== '\t') && (messageCounter + ref_length+1)== counter) //<-- this means the length of the message is same
{
word_counter += CheckFunctionn(ref_length, messageCounter + 1, argv[1], message);
}
messageCounter++;
}
fclose(input);
fclose(output);
return 0;
}

Answer 1

You're almost certainly failing to open the input file. If fopen fails, it returns NULL, and calling fgetc(NULL) has undefined behavior, and a segmentation fault is one possible outcome of undefined behavior.
You need to check for errors and handle then accordingly. You also need to check if your program was given sufficient arguments. Here's one way to handle them:
if (argc < 3)
{
fprintf(stderr, "Usage: %s input-file output-file\n", argv[0]);
exit(1);
}
input = fopen(argv[1],"r");
if (input == NULL)
{
fprintf(stderr, "Error opening input file %s: %s\n", argv[1], strerror(errno));
exit(1);
}
output = fopen(argv[2],"w");
if (output == NULL)
{
fprintf(stderr, "Error opening output file %s: %s\n", argv[2], strerror(errno));
exit(1);
}

Answer 2

You only read one character into c, then loop while(c != EOF) which is almost always an infinite loop. Inside that loop, you increment messageCounter which you use to walk past the end of an array -- boom!

Answer 3

Per your comment, argc is 2, but you refer to argv[2] which would be the third element of the args, and will be NULL. The FILE * is going to end up being NULL too (because it's invalid to pass NULL to fopen).

Answer 4

It will be very easy if you use strcmp function in this...
What you have to do is first find the length of ur file using ftell and after that allocate that much memory then fill that memory using fgetc or fgets or any other file function...then just use strcmp function on that....bingo!!!!! :)