C Programming: Extract a substring from a given string

Last update on October 24 2025 12:11:08 (UTC/GMT +8 hours)

13. Extract Substring

Write a program in C to extract a substring from a given string.

Sample Solution:

C Code:

#include <stdio.h>

int main() {
    char str[100], sstr[100]; // Declare two character arrays to store the main string and substring
    int pos, l, c = 0; // Declare variables for position, length, and a counter

    printf("\n\nExtract a substring from a given string:\n"); // Display information about the task
    printf("--------------------------------------------\n");

    printf("Input the string : ");
    fgets(str, sizeof str, stdin); // Read a string from the standard input (keyboard)

    printf("Input the position to start extraction :");
    scanf("%d", &pos); // Read the starting position for substring extraction

    printf("Input the length of substring :");
    scanf("%d", &l); // Read the length of the substring

    // Extracting the substring
    while (c < l) {
        sstr[c] = str[pos + c - 1]; // Copy characters from the specified position into the substring
        c++;
    }
    sstr[c] = '\0'; // Add null terminator to mark the end of the substring

    printf("The substring retrieved from the string is : \" %s\" \n\n", sstr); // Display the extracted substring
	
	return 0; // Return 0 to indicate successful execution of the program
}

Output:

Extract a substring from a given string:                                                                      
--------------------------------------------                                                                  
Input the string : This is test string                                                                        
Input the position to start extraction :9                                                                     
Input the length of substring :4                                                                              
The substring retrieve from the string is : " test "

Flowchart:

Flowchart: Extract a substring from a given string

For more Practice: Solve these Related Problems:

Write a C program to extract a substring from a string using pointer arithmetic based on a given start index and length.
Write a C program to extract and print a substring from the middle of a string without using library functions.
Write a C program to extract a substring, reverse it, and then display the reversed substring.
Write a C program to extract a substring from a string and convert the extracted part to uppercase before printing.

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