C language file operation: How to write files?

Steps to write files in C language: Use the fopen() function to open the file and specify the writing mode ("w" or "a"); use the fprintf() function to write data to the file; use the fclose() function to close the file.

C language file operation: write to file

In C language, writing files is a common operation to write data into files using FILE* pointer through fprintf() function. Here are the steps:

1. Open the file

• Use fopen() function to open the file and specify the write mode ("w" or "a").
• If the file is successfully opened, a FILE* pointer will be returned, otherwise NULL will be returned.

2. Write data

• Use the fprintf() function to write data to a file. The format is similar to the printf() function, but the first parameter is FILE* pointer.

3. Close the file

• Use the fclose() function to close the file.

Practical cases

Here is an example of writing strings to a file:

 #include <stdio.h>

int main() {
    FILE *fp;

    // Open the file fp = fopen("output.txt", "w");
    if (fp == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Write data fprintf(fp, "Hello, world!\n");

    // Close the file fclose(fp);

    return 0;
}

Run the program

After compiling and running the program, a file named output.txt is created, containing the "Hello, world!" string.

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