C string comparison program

strcmp():

• It is Pre-defined function in string.h header file.
• Check the input strings are having same content or not.
• IF equal, returns 0.
• If not equal, returns non zero.

#include<stdio.h>
#include<string.h>
int main()
{
	char s1[20] = "Hello";
	char s2[20] = "Hello";
	
	if(strcmp(s1,s2)==0)
		printf("Strings are equal \n");
	else
		printf("String are not equal \n");
}

• strcmp() function consider the case.
• Lower case characters and Upper case characters treats differently.

#include<stdio.h>
#include<string.h>
int main()
{
	char s1[20] = "hello";
	char s2[20] = "Hello";
	
	if(strcmp(s1,s2)==0)
		printf("Strings are equal \n");
	else
		printf("String are not equal \n");
}

stricmp() function will not consider the case:

#include<stdio.h>
#include<string.h>
int main()
{
	char s1[20] = "HELLO";
	char s2[20] = "Hello";
	
	if(stricmp(s1,s2)==0)
		printf("Strings are equal \n");
	else
		printf("String are not equal \n");
}

strncmp() function checks only n characters are equal or not from the beginning of the string.

#include<stdio.h>
#include<string.h>
int main()
{
	char s1[20] = "Hello all";
	char s2[20] = "Hello everyone";
	
	if(strncmp(s1,s2,5)==0)
		printf("Strings having identical start \n");
	else
		printf("Strings not having identical start\n");
}

Note: strncmp() function is case-sensitive

C program to compare two strings without using string functions

• strcmp() function compares two string character by character until there is a mismatch occurs or end of the one of those strings reached whichever occurs first.
• If the two strings are equal, it returns 0. If two strings are not equal, it returns the numerical ASCII difference between the two mismatching characters.

#include<stdio.h>
int stringCompare(char[],char[]);
int main()
{
	char str1[100],str2[100];
	int compare;
	printf("Enter first string: ");
	gets(str1);
	printf("Enter second string: ");
	gets(str2);
	compare = stringCompare(str1,str2);
	if(compare == 1)
		printf("Both strings are equal.\n");
	else
	{
		printf("Both strings are not equal\n");
		printf("the ascii difference between mismatching characters is :%d",compare);
	}
	return 0;
}
int stringCompare(char str1[],char str2[])
{
	int i=0,flag=0;
	while(str1[i]!='\0' && str2[i]!='\0')
	{
		if(str1[i]!=str2[i])
		{
			flag=1;
			break;
		}
		i++;
	}
	if (flag==0 && str1[i]=='\0' && str2[i]=='\0')
		return 1;
	else
		return str1[i]-str2[i];
}