C – Files Introduction

File: A collection of Data or Program or Records identified by a Name.

FILE* pointer:

• FILE is a pre-defined structure type variable.
• FILE* can points to any type of file.
• Once we make the pointer pointing to a file, then we can perform all FILE operations such as reading, writing, appending and so on.

Modes of Files:

Read mode(“r”):       

• Opens file in Read mode.
• If file is present, it opens and returns pointer to that file.
• If file is not present, it returns NULL pointer.

Write mode(“w”):     

• Opens file in Write mode.
• If file is present, it opens and removes the existing contents of File.
• If file is not present, it creates the new file with specified name.

Append mode(“a”): 

• Opens file in append mode.
• If file is present, it opens and places the cursor at the end of existing data to add the new contents.
• If file is not present, it creates the new file with specified name.

Opening a File:

• fopen() is a pre-defined function that opens a file in specified mode.
• On success, it opens and returns the pointer to file.
• On failure, it returns NULL pointer.

FILE*  fopen(char*  path, char* mode);

#include<stdio.h> int main() {             FILE* p;                        p = fopen(“c:/users/srinivas/desktop/code.c”, “r”);             if(p==NULL)                         printf(“No such file to open \n”);             else                         printf(“File opened in read mode \n”);             return 0; }