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fseek() function in C language with Example

Here, we are going to learn about the fseek() function of library header stdio.h in C language with its syntax, example.
Submitted by Souvik Saha, on January 24, 2019

fseek() function in C

Prototype:

    int feek(FILE *stream, long int offset, int origin);

Parameters:

    FILE *stream, long int offset, int origin

Return type: int

Use of function:

The fseek() function is used to set the file indicator pointer to the associate with the file stream according to the value of offset and starting point of the file. The prototype of the function fseek() is:

    int feek(FILE *stream, long int offset, int origin);

Here, the offset is number of bytes from the origin.

There are three macros in fseek() function:

1. SEEK_SET: Seek from start of file
2. SEEK_CUR: Seek from current location
3. SEEK_END: Seek from end of file

fseek() example in C

#include <stdio.h>
#include <stdlib.h>

int main()
{
    //Initialize the file pointer
    FILE* f;
    //Take a array of characters
    char ch[100];

    //Create the file for write operation
    f = fopen("includehelp.txt", "w");
    printf("Enter five strings\n");
    for (int i = 0; i < 4; i++) {
        //take the strings from the users
        scanf("%[^\n]", &ch);
        //write back to the file
        fputs(ch, f);
        //every time take a new line for the new entry string
        //except for last entry.Otherwise print the last line twice
        fputs("\n", f);
        //clear the stdin stream buffer
        fflush(stdin);
    }

    //take the strings from the users
    scanf("%[^\n]", &ch);
    fputs(ch, f);
    //close the file after write operation is over
    fclose(f);

    //open a file
    f = fopen("includehelp.txt", "r");
    printf("\n...............print the strings..............\n");
    while (!feof(f)) {
        //takes the first 100 character in the character array
        fgets(ch, 100, f);
        //and print the strings
        printf("%s", ch);
    }

    rewind(f);
    printf("\n...............print the position before print a strings S..............\n");

    fseek(f, 0, SEEK_SET);
    printf("the file indicator position is - %d\n", ftell(f));
    printf("\n...............print the position after print a strings ..............\n");
    fgets(ch, 100, f);
    printf("%s", ch);

    fseek(f, 0, SEEK_CUR);
    //print the current location
    printf("the file indicator position is - %d\n", ftell(f));
    printf("\n...............print the position after print all the strings ..............\n");

    fseek(f, 0, SEEK_END);
    printf("the file indicator position is - %d\n", ftell(f));

    //close the file
    fclose(f);

    return 0;
}

Output

C stdio.h Library Functions Programs »

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