FILE HANDLING IN C
File Handling concept in C language is used for store a data permanently in computer. Using this concept we can store our data in Secondary memory (Hard disk). All files related function are available in stdio.h header file.
How to achieve File Handling in C
For achieving file handling in C we need follow following steps
- Naming a file
- Opening a file
- Reading data from file
- Writing data into file
- Closing a file
Functions use in File Handling in C
S.No | Function | Operation |
1 | fopen() | To create a file |
2 | fclose() | To close an existing file |
3 | getc() | Read a character from a file |
4 | putc() | Write a character in file |
5 | fprintf() | To write set of data in file |
6 | fscanf() | To read set of data from file. |
5 | getw() | To read an integer from a file |
6 | putw() | To write an integer in file |
Defining and Opening a File
Data structure of file is defined as FILE in the standard I/O function. So all files should be declared as type FILE.
Before opening any file we need to specify for which purpose we open file, for example file open for write or read purpose.
Syntax
FILE *fp;
pf=fopen("filename", "mode");
Here fp declare a variable as a pointer to the data type FILE.
Closing a File
A file must be close after completion of all operation related to file. For closing file we need fclose()function.
Syntax
fclose(Filepointer);
File Opening mode
S.No | Mode | Meaning | Purpose |
1 | r | Reading | Open the file for reading only. |
2 | w | Writing | Open the file for writing only. |
3 | a | Appending | Open the file for appending (or adding) data to it. |
4 | r+ | Reading + Writing | New data is written at the beginning override existing data. |
5 | w+ | Writing + Reading | Override existing data. |
6 | a+ | Reading + Appending | To new data is appended at the end of file. |
Input/Output Operation on files
To perform Input/Output Operation on files we need below functions.
S.No | Function | Operation | Syntax | |
1 | getc() | Read a character from a file | getc( fp) | |
2 | putc() | Write a character in file | putc(c, fp) | |
3 | fprintf() | To write set of data in file | fprintf(fp, "control string", list) | |
4 | fscanf() | To read set of data from file. | fscanf(fp, "control string", list) | |
5 | getw() | To read an integer from a file. | getw(fp) | |
6 | putw() | To write an integer in file. | putw(integer, fp) |
Write data in File
Example
#include<stdio.h>
#include<conio.h>
void main()
{
FILE *fp;
char ch[20];
clrscr();
fp=fopen("Hello.txt", "w");// Creates in same Directory where ur C File is Saved
printf("Enter any Text: ");
scanf("%s",&ch); // Read data from keyboard
fprintf(fp,"%s",ch); // Write data in file
fclose(fp);
getch();
}
. Write a C program to read name and marks of n number of students from user and store them in a file.
#include <stdio.h>
int main()
{
char name[50];
int marks, i, num;
printf("Enter number of students: ");
scanf("%d", &num);
FILE *fptr;
fptr = (fopen("C:\\student.txt", "w"));
if(fptr == NULL)
{
printf("Error!");
exit(1);
}
for(i = 0; i < num; ++i)
{
printf("For student%d\nEnter name: ", i+1);
scanf("%s", name);
printf("Enter marks: ");
scanf("%d", &marks);
fprintf(fptr,"\nName: %s \nMarks=%d \n", name, marks);
}
fclose(fptr);
return 0;
}
2. Write a C program to read name and marks of n number of students from user and store them in a file. If the file previously exits, add the information of n students.
#include <stdio.h>
int main()
{
char name[50];
int marks, i, num;
printf("Enter number of students: ");
scanf("%d", &num);
FILE *fptr;
fptr = (fopen("C:\\student.txt", "a"));
if(fptr == NULL)
{
printf("Error!");
exit(1);
}
for(i = 0; i < num; ++i)
{
printf("For student%d\nEnter name: ", i+1);
scanf("%s", name);
printf("Enter marks: ");
scanf("%d", &marks);
fprintf(fptr,"\nName: %s \nMarks=%d \n", name, marks);
}
fclose(fptr);
return 0;
}
C program to find number of lines in a file
In this program, we are going to learn how to find total number of lines available in a text file using C program?
This program will open a file and read file’s content character by character and finally return the total number lines in the file. To count the number of lines we will check the available Newline (\n) characters.
File "test.text"
Hello friends, how are you?
This is a sample file to get line numbers from the file.
Program to get/find total number of lines in a file in C
#include <stdio.h>
#define FILENAME "test.txt"
int main()
{
FILE *fp;
char ch;
int linesCount=0;
//open file in read more
fp=fopen(FILENAME,"r");
if(fp==NULL)
{
printf("File \"%s\" does not exist!!!\n",FILENAME);
return -1;
}
//read character by character and check for new line
while((ch=fgetc(fp))!=EOF)
{
if(ch=='\n')
linesCount++;
}
//close the file
fclose(fp);
//print number of lines
printf("Total number of lines are: %d\n",linesCount);
return 0;
}
Output
Total number of lines are: 2
C Code Snippet - Read Content of a File using getc() using C Program
/*C - Read Content of a File using getc()
using C Program.*/
#include <stdio.h>
int main(){
//file nane
const char *fileName="sample.txt";
//file pointer
FILE *fp;
//to store read character
char ch;
//open file in read mode
fp=fopen(fileName,"r");
if(fp==NULL){
printf("Error in opening file.\n");
return -1;
}
printf("Content of file\n");
while((ch=getc(fp))!=EOF){
printf("%c",ch);
}
fclose(fp);
return 0;
}
Content of file
This is sample.txt file document.
------------------------------------------------------------------------------------------------------------------
Compile and Link C Program
There are three basic phases occurred when we execute any C program.
- Preprocessing
- Compiling
- Linking
Preprocessing Phase
A C pre-processor is a program that accepts C code with preprocessing statements and produces a pure form of C code that contains no preprocessing statements (like #include).
Compilation Phase
The C compiler accepts a preprocessed output file from the preprocessor and produces a special file called an object file. Object file contains machine code generated from the program
Linking Phase
The link phase is implemented by the linker. The linker is a process that accepts as input object files and libraries to produce the final executable program.
