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File Handling:
When a program is terminated, the entire data is lost. Storing in a file will preserve
your data even if the program terminates.
If you have to enter a large number of data, it will take a lot of time to enter them all.
However, if you have a file containing all the data, you can easily access the contents
of the file using a few commands in C.
You can easily move your data from one computer to another without any changes.
Types of Files
When dealing with files, there are two types of files you should know about:
Text files
Text files are the normal .txt files. You can easily create text files using any simple text editors such as Notepad. When you open those files, you'll see all the contents within the file as plain text. You can easily edit or delete the contents. They take minimum effort to maintain, are easily readable, and provide the least security and takes bigger storage space.
Binary files
Binary files are mostly the .bin files in your computer. Instead of storing data in plain text, they store it in the binary form (0's and 1's). They can hold a higher amount of data, are not readable easily, and provides better security than text files.
Working with files
When working with files, you need to declare a pointer of type file. This declaration is needed for communication between the file and the program.
Example:
FILE *fptr;
Opening a file - for creation and edit
Opening a file is performed using the fopen() function defined in the stdio.h header file.
Syntax:
ptr = fopen("fileopen","mode");
Closing a File
The file (both text and binary) should be closed after reading/writing. Closing a file is performed using the fclose() function.
Syntax:
fclose(fptr);
Reading a file:
In order to read a file, we can use fscanf function. This fuction is file version of sacnf function. fscanf expects a file pointer in addition to the other arguments which scanf expects. We will have to open the file in read mode in order to use this function.
Example:
#include<stdio.h> int main() { FILE *ptr = NULL; char str[50]; ptr = fopen("vc.txt","r"); fscanf(ptr,"%s",str ); printf("%s",str); fclose(ptr); return 0; }
Write to a file:
In order to write to a file, we can use fprintf function. This function is file version of printf function. fprintf expect a file pointer in addition to the other arguments which printf expects. We will have to open the file in write mode in order to use this function.
Example:
#include<stdio.h> int main() { FILE *ptr = NULL; char str[50]="Hello, World!"; ptr = fopen("vc.txt","w"); fprintf(ptr,"%s",str ); printf("%s",str); fclose(ptr); return 0; }
fgetc: Example: #include<stdio.h> int main() { FILE *ptr=NULL; ptr=fopen("vc.txt","r"); char c = fgetc(ptr); printf("The character is %c\n",c); fclose(ptr); return 0; } Example: #include<stdio.h> int main() { FILE *ptr=NULL; ptr=fopen("vc.txt","r"); char c = fgetc(ptr); printf("The character is %c\n",c); c = fgetc(ptr); printf("The character is %c\n",c); fclose(ptr); return 0; }
Example: #include<stdio.h> int main() { FILE *ptr=NULL; int i,n; char c; ptr=fopen("vc.txt","r"); n = sizeof(ptr); for(i=0;i<=n;i++) { c=fgetc(ptr); printf("%c",c); } fclose(ptr); return 0; }
fputs: Examples: #include<stdio.h> int main() { FILE *ptr=NULL; ptr=fopen("vc.txt","w"); fputs("Hello, World!",ptr); fclose(ptr); return 0; } r+ : Example: #include<stdio.h> int main() { FILE *ptr=NULL; ptr=fopen("vc.txt","r+"); fputs("World!",ptr); fclose(ptr); return 0; }
w+ : Example: #include<stdio.h> int main() { FILE *ptr=NULL; ptr=fopen("vc.txt","w+"); fputs("World!",ptr); fclose(ptr); return 0; } a+ : Example: #include<stdio.h> int main() { FILE *ptr=NULL; ptr=fopen("vc.txt","a+"); fputs("World!",ptr); fclose(ptr); return 0; }
