Difference between revisions of "C-and-C++/C4/File-Handling-In-C/English"

To open a file.

To read data from a file.

To write data into a file.

Few examples.

Ubuntu Operating System version 11.10,

gcc Compiler version 4.6.1.

File is a collection of data.

It can be a database, a program, a letter or anything.

We can create a file and access it using C.

Now let us see an example on file handling in C.

file.c

Let's take a look.

Note that our filename is file.c

In this program we will create a file and write data into it.

#include <stdio.h>

This is our header file.

int main()

FILE *fp;

The FILE variable is defined under the header stdio.h

*fp is a pointer to the FILE variable.

It will store all the information about the file.

Like its name, status and current information.

Let us go back to our slides.

fp = fopen(“filename”, “mode”);

Here, the fopen function opens a stream.

Then it links the file with the stream.

The filename is the name of the file that we want to open or create.

We can give the path along with the filename.

We can also give the extension.

Here we can give the mode of the file.

w - creates file for read and write.

r - opens file for reading.

a – writing at the end of file.

fp = fopen(“Sample.txt”, “w”);

Here, we create a Sample.txt file in write mode.

We can see that the path is given.

Our file will be created on the desktop.

fprintf(fp,"This is just an example\n");

"Welcome to the spoken-tutorial" and

"This is an test example"

fprintf writes output to the given output stream.

fclose(fp);

return 0;

Ctrl, Alt and T keys

Open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard

gcc file.c -o file

Type

./file

gcc file.c -o file

Press Enter

To execute, type

./file

Press Enter

Now we will check it out.

Click on the home folder option.

Now click on the Desktop option.

This shows that our file is successfully created.

Double click on the file.

We can see the messages here.

Welcome to the Spoken Tutorial.

This is an test example.

This is how we create a file and write data into it.

I will open it.

In this program we will read data from our sample.txt file and print the data on the console.

Let me explain the code now.

#include <stdio.h>

int main()

FILE *fp

char c;

fp = fopen("Sample.txt","r");

The output is stored in fp.

if (fp == NULL)

printf("File doesn't exist\n");

If fp is equals to NULL.

If the condition is true, then we print the message:

"File doesn't exist."

else

{

while (c != EOF)

While c is not equal to EOF.

Here, EOF is the end of file.

It denotes the end of input.

It is a condition where no more data can be read from a data source.

c = getc(fp);

Here, getc returns a character from a specified file or stream.

Now, it will return a character from our Sample.txt file.

putchar(c);

Then it will store the characters in variable c.

fclose(fp);

return 0;

gcc readfile.c -o read

Type

./read

gcc readfile.c -o read

Now press Enter

To execute, type

./read

Output

Welcome to the Spoken-Tutorial.

This is an test example.

In this tutorial we learnt,

• File handling.

• To write data into a file.

• eg. fp = fopen(“Sample.txt”, “w”);

• To read data from a file.

• eg. fp = fopen(“Sample.txt”, “r”);

Assignment

Write a program to create a file TEST.

Write your name and address in the file TEST.

Then display it on the console using C program.

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

About the Spoken Tutorial Project

It summarises the Spoken Tutorial project

If you do not have good bandwidth, you can download and watch it

Spoken Tutorial Workshops

Conducts workshops using spoken tutorials

Gives certificates to those who pass an online test

For more details, please write to

contact@spoken-tutorial.org

Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of India

More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro

Thank You for watching.