Thread: 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:

#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;
}

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.

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