CODEWITHSUNDEEP
cstring
Andy_A̷n̷d̷y̷
Andy_A̷n̷d̷y̷

Reputation: 795

Comparing String Arrays in C

This is the code:

#include <stdio.h>


int main(void)
{
    char words[256];
    char filename[64];
    int count = 0;

    printf("Enter the file name: ");
    scanf("%s", filename);

    FILE *fileptr;
    fileptr = fopen(filename, "r");

    if(fileptr == NULL)
        printf("File not found!\n");

    while ((fscanf(fileptr, " %s ", words))> 0)
    {
        if (words==' ' || words == '\n')
        count++;
    }

    printf("%s contains %d words.\n", filename, count);

    return 0;

}

I keep getting this error: 

warning: comparison between pointer and integer [enabled by default]
         if (words==' ' || words == '\n')
                  ^


I don't get the error once I change, words to *words but that does not give me the correct results. I am trying count the number of words in a file.

Upvotes: 0

Views: 259

Answers (5)

ajay
ajay

Reputation: 9680

You cannot compare strings in C. You should compare them character by character using the standard library function strcmp. Here's its prototype contained in the string.h header.

int strcmp(const char *s1, const char *s2);

The strcmp function compares the two strings s1 and s2. It returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be less than, to match, or be greater than s2.

The format string of fscanf " %s " (note the trailing and the leading space) will read and discard any number of whitespaces which it does anyway with the format string "%s". This means no whitespaces will be written into the buffer words by fscanf. fscanf will write only non-whitespace characters in words and returns when it encounters a whitespace. So, to count the number of words, just increase the counter for each successful fscanf call.

Also, your program should check for possible buffer overflow in scanf and fscanf calls. If the input string is too big for the buffer, then this would cause undefined behaviour and even causing crash due to segfault. You can guard against it by changing the format string. scanf("%63s", filename); means scanf will read from stdin until it encounters a whitespace and write at most 63 non-whitespace characters in the buffer filename and then add a terminating null byte at the end. 

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

int main(void) {
    // assuming max word length is 256
    // +1 for the terminating null byte added by scanf
    char words[256 + 1]; 

    // assuming max file name length is 64
    // +1 for the terminating null byte 
    char filename[64 + 1]; 

    int count = 0;        // counter for number of words

    printf("Enter the file name: ");
    scanf("%64s", filename);

    FILE *fileptr;
    fileptr = fopen(filename, "r");

    if(fileptr == NULL)
        printf("File not found!\n");

    while((fscanf(fileptr, "%256s", words)) == 1)
        count++;

    printf("%s contains %d words.\n", filename, count);
    return 0;

}

Upvotes: 0

BLUEPIXY
BLUEPIXY

Reputation: 40145

not necessary compare because %s(words) does not contain white spaces(e.g. ' ' or '\n').

try this 

while (fscanf(fileptr, "%s", words)> 0) {
    count++;
}

Upvotes: 1

Rami
Rami

Reputation: 7290

Take care that using the array name words by itself implies a pointer to the first element in the array. If what you need is to compare 2 strings in C then the strcmp is what you are looking for.

Upvotes: 0

michaeltang
michaeltang

Reputation: 2898

words is char pointer while ' ' is char, *words equals to words[0] usually we would define a new pointer as below

char *p =  words;
while(*p != '\0' )
{
  // using *p something you need to do 
  p++;
}

Upvotes: 1

Sadique
Sadique

Reputation: 22813

There is no string in C. Every string (/ literal) is an Array of chars. Use strcmp

Upvotes: 0

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