calloc() and malloc() in C

fseek()

The fseek() in C language is used to move the file pointer to a specific position. The offset and stream are the destination of the pointer, given in the function parameters. If successful, it returns zero, otherwise it returns a non-zero value.

This isfseek()C language syntax

int fseek(FILE　*stream, long int offset, int whence)

This is the parameter used infseek(),

• stream-This is the pointer that identifies the stream.

• offset-This is the number of bytes from the position.

• whence-This is the position where the offset is added.

Is specified by one of the following constants.

• SEEK_END-The end of the file.

• SEEK_SET-The beginning of the file.

• SEEK_CUR-The current position of the file pointer.

This isfseek()C language example-

Suppose we have the following content in the "demo.txt" file-

This is demo text!
This is demo text!
This is demo text!
This is demo text!

Now let's look at the code.

Example

#include<stdio.h>
void main() {
　　　FILE　*f;
　　　f = fopen("demo.txt", "r");
　　　if(f == NULL) {
　　　　　　printf("\nCan't open file or file doesn't exist.");
　　　　　　exit(0);
　　　}
　　　fseek(f, 0, SEEK_END);
　　　printf("The size of the file: %ld bytes", ftell(f));
　　　getch();
}

Output result

The size of the file:　78　bytes

In the above program, the file "demo.txt" is opened usingfopen();andfseek()The method is used to move the pointer to the end of the file.

f = fopen("demo.txt", "r");
if(f == NULL) {
　　　printf("\nCan't open file or file doesn't exist.");
　　　exit(0);
}
fseek(f, 0, SEEK_END);

rewind()

The functionrewind();Used to set the position of the file to the beginning of the given stream. It does not return any value.

This isrewind();C language syntax

void rewind(FILE　*stream);

This isrewind();C language example

Suppose we have the following content in the "new.txt" file-

This is demo!
This is demo!

Now, let's look at an example.

Example

#include<stdio.h>
void main() {
　　　FILE　*f;
　　　f = fopen("new.txt", "r");
　　　if(f == NULL) {
　　　　　　printf("\nCan't open file or file doesn't exist.");
　　　　　　exit(0);
　　　}
　　　rewind(f);
　　　fseek(f, 0, SEEK_END);
　　　printf("The size of the file: %ld bytes", ftell(f));
　　　getch();
}

Output result

The size of the file:　28　bytes

In the above program, the file is opened usingfopen();If the pointer variable is null, display that the file cannot be opened or the file does not exist. This functionrewind();Move the pointer to the beginning of the file.

f = fopen("new.txt", "r");
if(f == NULL) {
　　　printf("\nCan't open file or file doesn't exist.");
　　　exit(0);
}
rewind(f);