Help with user file I/O

Hello,

I am teaching myself C, and am having difficulty writing to a user-specified file. In the code below, fopen keeps returning a null file pointer. When the file location is physically written in the code, however, the program works as expected. My question has two parts:

1) Why does fopen return a null pointer?
2) What should I change to make the program accept user-specified input files?

I have not been able to find an answer to these questions in my C book or through online searches.

Note: The code is written and compiled in Microsoft Visual C++ 2008, if that makes a difference.

Code:

---

#define _CRT_SECURE_NO_WARNINGS
#define MAX_FILE 100
#define MAX_TEXT 50

#include <stdio.h>

int main()
{
        char file_location[MAX_FILE];
        char text[MAX_TEXT];
        FILE *myfile;
       
        printf("Enter file location: ");
        fgets(file_location, MAX_FILE, stdin);
        myfile = fopen(file_location,"w");
        //myfile = fopen("c:/c test files/test.txt","w"); //PROGRAM WORKS IN THIS CASE

        if (myfile != NULL)
        {
                printf("Enter your text: ");
                fgets(text, MAX_TEXT, stdin);
                fprintf(myfile, text);
        }
        else
        {
                printf("INVALID FILE PATH.\n");
                return 0;
        }
       
        fclose(myfile);

        return 0;
}

---

Thank you for any assistance.

Remove the newline from your buffer after you call fgets on it.


Quzah.

Thank you, quzah.

For anybody's reference, here is the revised (and working!) code:

Code:

---

#define _CRT_SECURE_NO_WARNINGS
#define MAX_FILE 100 //maximum length of file_location string, including termination character
#define MAX_TEXT 50 //maximum length of text string, including termination character

#include <stdio.h>

int main()
{
        char file_location[MAX_FILE];
        char text[MAX_TEXT];
        int i; //loop counter
        FILE *myfile;
       
        printf("Enter file location: "); //note: fopen doesn't like creating new directories
        fgets(file_location, MAX_FILE, stdin);
       
        for (i=0; i<MAX_FILE; i++) //replace newline character with string termination character
        {
                if (file_location[i] == '\n'){
                        file_location[i] = '\0';
                }
        }

        printf("File location: %s\n",file_location);
        myfile=fopen(file_location,"w");

        if (myfile != NULL) //checks if file is valid
        {
                printf("Enter your text: ");
                fgets(text, MAX_TEXT, stdin);
                fprintf(myfile, text);
        }
        else
        {
                printf("INVALID FILE PATH.\n");
                return 0;
        }
       
        fclose(myfile);

        return 0;
}

---

1. your loop for replacing \n with \0 could be exitted as soon as the \n or \0 char is encountered - no sence to continue
2. using user provided string as a format for printf is a big security hole. - You should replace fprintf with fputs or use "%s" format in fprintf