C language file operation: How to read files?

C language file operation: read files

Introduction

File processing is a crucial part of C programming, which allows programs to interact with external storage devices such as disks and flash drives. This article will explore how to read files in C.

Steps to read a file

1. Open file: Use the fopen function to open the file. This function requires two parameters: file name and open mode.
2. Check whether the file is open: Check whether the pointer returned by fopen function is NULL . If NULL , the file cannot be opened.
3. Read file: Use the fread function to read data from the file to the buffer. This function requires four parameters: buffer address, buffer element size, number of elements to be read, and file pointer.
4. Close file: Use the fclose function to close the file.

Practical cases

Consider the following C program that reads the file data.txt and prints its contents:

 #include <stdio.h>

int main() {
    FILE *file;
    char buffer[100];

    // Open file file = fopen("data.txt", "r");

    // Check if the file is open if (file == NULL) {
        printf("Cannot open file!\n");
        return 1;
    }

    // Read file while (fread(buffer, sizeof(char), 100, file) > 0) {
        printf("%s", buffer);
    }

    // Close the file fclose(file);

    return 0;
}

explain

• The fopen function opens the file data.txt in read-only mode.
• The fread function reads the file line by line and stores it in the buffer buffer .
• while loop continues to read until the end of the file.
• The printf function prints the contents in the buffer.
• The fclose function closes the file.

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