Last Updated on March 30, 2023 by Prepbytes
As we know built-in functions are available in a language to reduce the complexity of our code and save the coder time. Built-in functions are predefined functions that a programmer can use to execute a statement without explicitly coding, strcpy() is an example of a built-in function that copies one string to another. In this section, we will look at the strstr function C programming language. The strstr function in C is one of the built-in library functions that will attempt to understand its significance in C programming and how to implement the strstr function in C programs.
What is the strstr() Function in C?
The strstr function in c is a predefined function for string handling. < string.h> is the header file required for string functions. The strstr function in c takes two strings s1 and s2 as arguments and finds the first occurrence of the substring s2 in the string s1. The matching process does not include the terminating null characters (‘0’), but the function terminates there. In simple words, The strstr function is a useful library function in C programming that is used to find a substring within a string
Syntax of strstr() Function in C
Here we have the syntax of strtstr function in c
char *strstr(const char *string, const char *substring);strstr function in c takes two arguments, the first argument is a string and second argument is substring,so strstr function re3turn pointer to first occurrence of the substring within the string
Let’s take a closer look at the parameters and return value of the strstr() function:
Parameters of strstr() Function in C
The strstr() function takes two parameters:
- string – This is a pointer to the string that is to be searched.
- substring – This is a pointer to the substring that is to be searched for within the string.
Both the string and substring arguments must be null-terminated strings.
Return Value of strstr() Function in C
The strstr() function returns a pointer to the first occurrence of the substring within the string, or a null pointer if the substring is not found.
If the substring is an empty string, then the strstr() function returns a pointer to the string.
Example of strstr() Function in C
Let’s look at an example to understand how the strstr() function works:
#include <stdio.h>
#include <string.h>
int main() {
char string[50] = "Hello, World!";
char substring[10] = "World";
char *result;
result = strstr(string, substring);
printf("The substring is: %s\n", result);
return 0;
} Output
The substring is: World!Explanation
In this example, we have a string Hello, World!, and we are searching for the substring World within the string using the strstr() function. The function returns a pointer to the first occurrence of the substring within the string, which is then stored in the result variable. Finally, the printf() function is used to print the value of the result variable, which contains the first occurrence of the substring World within the string Hello, World!. The output of the program is:
In this example, the strstr() function has found the first occurrence of the substring World within the string Hello, World! and returned a pointer to that substring. If the substring was not found, then the strstr() function would have returned a null pointer.
Conclusion
The strstr function in C searches the main string for a given substring and returns the pointer to the first occurrence of that substring. To use the strstr function in the C program, we must include string.h header at the beginning of the C program. If there is no occurrence of the required substring in the main string, the function returns a NULL pointer; otherwise, a character pointer from the first occurrence to the end of the main string is returned. the strstr() function is a powerful library function in C programming that is used to search for substrings within a string. With its simple syntax and powerful functionality, the strstr() function is a valuable tool for any C programmer.
Frequently Asked Question
Here are the FAQ on the strstr function in c:
Q1. How does the strstr function in c work?
Ans. The strstr function searches for the first occurrence of the substring str2 within the string str1. It starts at the beginning of str1 and checks if str2 matches a portion of str1. If it does not find a match, it moves on to the next character in str1 and repeats the process. If it does find a match, it returns a pointer to the location in str1 where the match starts.
Q2. Does the strstr function in c modify the original string?
Ans. No, the strstr function does not modify the original string. It only searches for the substring.
Q3. Can the strstr function in c be used with Unicode strings?
Ans. Yes, the strstr function can be used with Unicode strings, but only if they are encoded as ASCII or UTF-8. If the strings are encoded as UTF-16 or UTF-32, you may need to use a different function that is specifically designed for Unicode strings.
Q4. What happens if either the str1 or str2 argument passed to strstr function is NULL?
Ans. If either the str1 or str2 argument passed to the strstr function is NULL, the function will result in undefined behavior.
Q5. Can the strstr function be used to search for multiple occurrences of a substring within a string?
Ans. Yes, the strstr function can be used to search for multiple occurrences of a substring within a string. You can use a loop to repeatedly call strstr with the updated pointer to continue searching for additional occurrences of the substring.
Q6. Is the strstr function in c case-sensitive?
Ans. Yes, the strstr function is case-sensitive. This means that it will only find occurrences of the substring that match the case of the characters in the original string.
Q7. Can the strstr function be used to search for substrings that contain null characters?
Ans. No, the strstr function cannot be used to search for substrings that contain null characters. This is because null characters are used to terminate C-style strings, so if a null character is encountered within the substring argument, the function will terminate the search prematurely.
Q8. Is there any alternative to the strstr function in C?
Ans. Yes, there are several alternative functions to strstr in C that can be used to search for substrings within a string, including strcasestr (case-insensitive search), memmem (memory-based search), and strchr (search for a single character). The choice of function depends on the specific requirements of the program.