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This Section Shows some examples pf actions that can be done on Strings in C.

How to Read a String From User?

// C program to read string from user
#include<stdio.h>
	
int main()
{
	// declaring string
	char str[50];
		
	// reading string
	scanf("%s",str);
		
	// print string
	printf("%s",str);
	
	return 0;
}

Input:

RishiJoshi

Output:

RishiJoshi

How to Read a Line of Text in C?

We can use the fgets() function to read a line of string and gets() to read characters from the standard input (stdin) and store them as a C string until a newline character or the End-of-file (EOF) is reached.

For Example:

// C program to illustrate
// fgets()
#include <stdio.h>
#define MAX 50
int main()
{
	char str[MAX];

	// MAX Size if 50 defined
	fgets(str, MAX, stdin);

	printf("String is: \n");

	// Displaying Strings using Puts
	puts(str);

	return 0;
}

Input:

RishiJoshi

Output:

String is:
RishiJoshi

Appendment

Given a string str and a character ch, in the following example, we are going to see how to append this character ch to this string str at the end.

Examples:

Input: str = "Geek", ch = 's' Output: "Geeks"

Input: str = "skee", ch = 'G' Output: "skeeG"

Approach:

Get the string str and character ch
Use the strncat() function to append the character ch at the end of str. strncat() is a predefined function used for string handling. string.h is the header file required for string functions.

Syntax:

char *strncat(char *dest, const char *src, size_t n)

Parameters: This method accepts the following parameters:

dest: the string where we want to append.

src: the string from which ‘n’ characters are going to append.

n: represents the maximum number of character to be appended. size_t is an unsigned integral type.

Print or return the appended string str.

Below is the implementation of the above approach:

// C program to Append a Character to a String
 
#include <stdio.h>
#include <string.h>
 
int main()
{
    // declare and initialize string
    char str[6] = "Geek";
 
    // declare and initialize char
    char ch = 's';
 
    // print string
    printf("Original String: %s\n", str);
    printf("Character to be appended: %c\n", ch);
 
    // append ch to str
    strncat(str, &ch, 1);
 
    // print string
    printf("Appended String: %s\n", str);
 
    return 0;
}

Output:

Original String: Geek


Character to be appended: s


Appended String: Geeks

strncat()

In C, strncat() is a predefined function used for string handling. string.h is the header file required for string functions. This function appends not more than n characters from the string pointed to by src to the end of the string pointed to by dest plus a terminating Null-character. The initial character of the string(src) overwrites the Null-character present at the end of a string(dest). Thus, the length of the string(dest) becomes strlen(dest)+n. But, if the length of the string(src) is less than n, only the content up to the terminating null-character is copied and the length of the string(dest) becomes strlen(src) + strlen(dest). The behavior is undefined if –

The strings overlap. The dest array is not large enough to append the contents of src. Syntax:

char *strncat(char *dest, const char *src, size_t n)

Parameters: This method accepts the following parameters:

dest: the string where we want to append.

src: the string from which ‘n’ characters are going to append.

n: represents a maximum number of characters to be appended. size_t is an unsigned integral type.

Return Value: The strncat() function shall return the pointer to the string(dest).

Application Given two strings src and dest in C, we need to append ‘n’ character from src to dest, let’s say n=5.

Examples:

Input: src = "world" dest = "Hello" Output: "Hello world"

Program:

// C program demonstrate functionality of strncat()
#include <stdio.h>
#include <string.h>

int main()
{

// Take any two strings
char src[50] = "efghijkl";
char dest[50]= "abcd";

// Appends 5 character from src to dest
strncat(dest, src, 5);
	
// Prints the string
printf("Source string : %s\n", src);
printf("Destination string : %s", dest);
	
return 0;
}

Output:

Source string : efghijkl
Destination string : abcdefghi

How strncat() is different from strcat() ?

It is recommended by many of the programmers that strncat() is safe as compared to strcat() because strcat() does not check for the size of the copied data, and copies until it gets to a null terminator, it might cause a buffer overflow while strncat() check for the size of the copied data, and will copy only ‘n’ bytes.

Program:

// C,C++ program demonstrate difference between
// strncat() and strcat()
#include <stdio.h>
#include <string.h>

int main()
{

// Take any two strings
char src[50] = "rishi";
char dest1[50] = "joshi";
char dest2[50] = "hey";

printf("Before strcat() function execution, ");
printf("destination string : %s\n", dest1);
	
// Appends the entire string of src to dest1
strcat(dest1, src);

// Prints the string
printf("After strcat() function execution, ");
printf("destination string : %s\n", dest1);

printf("Before strncat() function execution, ");
printf("destination string : %s\n", dest2);
	
// Appends 3 characters from src to dest2
strncat(dest2, src, 3);
	
// Prints the string
printf("After strncat() function execution, ");
printf("destination string : %s\n", dest2);
	
return 0;
}

Output:

Before strcat() function execution, destination string : joshi
After strcat() function execution, destination string : joshirishi
Before strncat() function execution, destination string : hey
After strncat() function execution, destination string : heyris

strpbrk()

This function finds the first character in the string s1 that matches any character specified in s2 (It excludes terminating null-characters).

Syntax :

char *strpbrk(const char *s1, const char *s2)

Parameters : s1 : string to be scanned. s2 : string containing the characters to match.

Return Value : It returns a pointer to the character in s1 that matches one of the characters in s2, else returns NULL.

// C code to demonstrate practical application
// of strpbrk
#include <stdio.h>
#include <string.h>

// Driver function
int main()
{
	// Initializing victory string
	char s1[] = "victory";

	// Declaring lottery strings
	char s2[] = "a23";
	char s3[] = "i22";
	char* r, *t;

	// Use of strpbrk()
	r = strpbrk(s1, s2);
	t = strpbrk(s1, s3);

	// Checks if player 1 has won lottery
	if (r != 0)
		printf("Congrats u have won");
	else
		printf("Better luck next time");

	// Checks if player 2 has won lottery
	if (t != 0)
		printf("\nCongrats u have won");
	else
		printf("Better luck next time");

	return (0);
}

Output:

Better luck next time Congrats u have won

strcoll()

strcoll() is a built-in library function and is declared in <string.h> header file. This function compares the string pointed to by str1 with the one pointed by str2.The strcoll() function performs the comparison based on the rules of the current locale’s LC_COLLATE category. Syntax:

int strcoll(const char *str1, const char *str2) Parameters: Function strcoll() takes two strings as parameters and returns an integer value.

Value Meaning less than zero str1 is less than str2 zero str1 is equal to str2 greater than zero str1 is greater than str2

less than zero : When str1 is less than str2

// C program to illustrate strcoll()
#include <stdio.h>
#include <string.h>

int main()
{
	char str1[13];
	char str2[13];
	int ret;

	strcpy(str1, "RISHIJOSHI");
	strcpy(str2, "lovesfootball");

	ret = strcoll(str1, str2);

	if (ret > 0) {
		printf("str1 is greater than str2");
	} else if (ret < 0) {
		printf("str1 is lesser than str2");
	} else {
		printf("str1 is equal to str2");
	}

	return (0);
}

Output:

str1 is lesser than str2

greater than zero :when str1 is greater than str2

// C program to illustrate strcoll()
#include <stdio.h>
#include <string.h>

int main()
{
	char str1[13];
	char str2[13];
	int ret;

	strcpy(str1, "geeksforgeeks");
	strcpy(str2, "GEEKSFORGEEKS");

	ret = strcoll(str1, str2);

	if (ret > 0) {
		printf("str1 is greater than str2");
	} else if (ret < 0) {
		printf("str1 is lesser than str2");
	} else {
		printf("str1 is equal to str2");
	}

	return (0);
}

Output: str1 is greater than str2

Is equal to zero : when str1 is equal to str2

// C program to illustrate strcoll()
#include <stdio.h>
#include <string.h>

int main()
{
	char str1[13];
	char str2[13];
	int ret;

	strcpy(str1, "FOOTBALL");
	strcpy(str2, "FOOTBALL");

	ret = strcoll(str1, str2);

	if (ret > 0) {
		printf("str1 is greater than str2");
	} else if (ret < 0) {
		printf("str1 is lesser than str2");
	} else {
		printf("str1 is equal to str2");
	}

	return (0);
}

Output: str1 is equal to str2

Length

Below is the algorithm for finding the length of two strings:

SET LEN = 0 AND I = 0.
Repeat Steps 3 to 4 while STRING[I] is not NULL:
LEN = LEN + 1.
SET I = I + 1.
Exit.

Programming Example:

/*
 * C program to find the length of a string without using the
 * built-in function
 */
 
#include <stdio.h>
 
void main()
{
    char string[50];
    int i, length = 0;
 
    // input the string
    printf("Enter the string: \n");
    gets(string);
    /*  keep going through each character of the string till its end */
    for (i = 0; string[i] != '\0'; i++)
    {
        length++;
    }
    printf("The length of a string is the number of characters in it \n");
    printf("So, the length of %s = %d\n", string, length);
}

Output:

Enter a string: Hello


The length of a string is the number of characters in it


So, the length of Hello = 5

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More Strings

How to Read a String From User?

How to Read a Line of Text in C?

Appendment

strncat()

strpbrk()

strcoll()

Length