字符数组在文件处理中不起作用

Question

What i was trying to do is, create a program that asks the user to enter how much long text he want to write. And after than whatever he writes in the console gets automatically saved in a textfile named file at following path mentioned in the code. So, to ask user the size of character array i used int i . And then used gets command to pick up whatever he wrote as it is with spaces and other characters. But the code doesn't seem to work it asks the user about how many character and then runs complete and terminates. Also tell me what should do to make it create a new file in Data folder everytime user starts the program? I don't want to overwrite the existing file or append text to it. I want to create a new file and let the user name it whatever he feels like and then store that text in that new file.

#include <stdio.h>
#include <stdlib.h>

int main()
{
FILE *file = fopen("C://Users//Abhimanyu Aryan//Desktop//Data//Hello.txt", "w");

printf("\t\tThis program allows you to write detailed data\n\n\n");

int c;
printf("you many characters file you want to write? Specify: ");
scanf("%i",&c);

printf("\n\nEnter your text here: ");

char text[c];

gets(text);


fprintf(file, "%s" , text);

printf(" the file has been written succesfully!!!!");

fclose(file);

return 0;

}

Answer 1

There are a couple of things wrong with your code. First, you should check the return value from fopen() to make sure everything was successful:

FILE *file = fopen("C://Users//Abhimanyu Aryan//Desktop//Data//Hello.txt", "w");
if (file == NULL) {
    /* Handle fopen() error */
    fprintf(stderr, "Couldn't open file for writing!");
    exit(EXIT_FAILURE);
}

The second mistake is that you are using gets() . gets() is old, deprecated and unsafe, you should never use it . Use fgets() instead:

char text[c];

fgets(text, sizeof text, stdin);

If you want the user to choose the filename, it's a matter of asking him first, and then open the specified filename for writing. If the file doesn't exist, it will automatically be created:

#define MAX_FILENAME_LENGTH 128

char filename[MAX_FILENAME_LENGTH];
printf("Enter filename (max. %zu characters): ", sizeof(filename)-1);
fgets(filename, sizeof filename, stdin);

FILE *file = fopen(filename, "w");
if (file == NULL) {
    /* Handle fopen() error as mentioned above*/
}

UPDATE :

Note that scanf("%i", &c); will leave a newline on the buffer (from when you press the ENTER key). That's why fgets() is returning prematurely without waiting: it reads a newline left on the buffer from the previous input and assumes you're done ( fgets stops when it hits a newline). To fix it, you have to consume the buffered newline before calling scanf() . You can do so with getchar() , for example:

/* ... */
scanf("%i",&c);
/* Consume newline left on buffer from scanf */
if (getchar() == '\r')
    (void) getchar();
printf("\n\nEnter your text here: ");
/* ... */

The if (gethcar() == '\\r') is there to make the code work in the case that stdin was redirected to a file with DOS end-of-lines ( \\r\\n rather than only \\n ), in which case 2 characters must be consumed. Even if you plan to use this from the terminal only (without stdin redirecton), I would still recommend leaving it that way - pressing ENTER might push \\r\\n to stdin too.

Answer 2

I would change

FILE *file = fopen("C://Users//Abhimanyu Aryan//Desktop//Data//Hello.txt", "w");

to

FILE *file = fopen("C:/Users/Abhimanyu Aryan/Desktop/Data/Hello.txt", "w");

or

FILE *file = fopen("C:\\Users\\Abhimanyu Aryan\\Desktop\\Data\\Hello.txt", "w");

I don't know that having two forward slashes as directory separator causes any problems but it is certainly not necessary.