Help, weird output

Hi, first post. I'm trying to read numbers from a file with strtok and for some reason the last value in the file is printed twice.
[Example] input: 1 2 5 word 4
output: 1 2 5 4 4

Code:

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 100
int isNumeric(char*);
int main (int argc,char* argv[]){
        if(argc!=2){
                puts("Usage: ./HW1 <filename>.txt");
                return 0;
        }
        FILE* cfPtr;
        if((cfPtr=fopen(argv[1],"r"))==NULL){
                puts("File could not be opened");
                return 0;
        }
        double test;
        char line[SIZE];
        char* strPtr;
        char* tokenPtr;
        while(!feof(cfPtr)){
                fgets(line,SIZE,cfPtr);
                tokenPtr=strtok(line," \t\n");
                while(tokenPtr!=NULL){
                        printf("tokenPtr:%s\n",tokenPtr);
                        if(isNumeric(tokenPtr)){
                                test=strtod(tokenPtr,&strPtr);
                                printf("%.0f\n", test);
                        }
                        tokenPtr = strtok(NULL," \t\n");
                }
        }
        fclose(cfPtr);
        return 0;
}
int isNumeric(char* token){
        int i=0;
        if(token[i]=='-'){
                ++i;
        }
        if(token[i]=='\0'){
                return 0;
        }
        while(token[i]!='\0'){
                if(isdigit(token[i])==0){
                        return 0;
                }
                ++i;
        }
        return 1;
}

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Isn't the extra character a 1 and not a 4?

The problem is that you are not checking the return value of fgets(). From the linked page:

Quote:

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If the end-of-file is encountered while attempting to read a character, the eof indicator is set (feof). If this happens before any characters could be read, the pointer returned is a null pointer (and the contents of str remain unchanged).

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You probably have a newline at the end of your input.
fgets() reads the first line and later tries to read the second - which is empty - and returns NULL. Because it doesn't modify your string in this case, line still has the old contents (which is something like ['1', '\0', '2', '\0', ...], because of the operations done by strtok()). So the next call to strtok() reads the 1 from line and stops at the NULL character, but this gets printed to the screen as it's a valid number.

Quote:

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Originally Posted by koplersky

Isn't the extra character a 1 and not a 4?

The problem is that you are not checking the return value of fgets(). From the linked page:



You probably have a newline at the end of your input.
fgets() reads the first line and later tries to read the second - which is empty - and returns NULL. Because it doesn't modify your string in this case, line still has the old contents (which is something like ['1', '\0', '2', '\0', ...], because of the operations done by strtok()). So the next call to strtok() reads the 1 from line and stops at the NULL character, but this gets printed to the screen as it's a valid number.

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Thank you, this fixed the problem. It's been a long winter break and I'm a bit rusty.