String functions: strlen, strcmp, strrev, strcpy, strlwr, strupr
String handling functions
Definition of String:
String is the set of characters,digits and symbols. We can also define string as the array of characters. The end of the string is marked with a special character , the ‘\0’ that means Null character. The size in a character string represents the maximum number of characters that the string can hold.
POINTS TO REMEMBER
A string is an array of characters. It contains characters, symbols, numbers etc.
Syntax:
char string_name[string_size];
As in above syntax, char refers to the character data type that will be stored in the array, string_name is the name of the string variable and string_size indicates the number of characters that can be stored inside the array.
Example
char name[10];
char address[10];
This declares the name as a character array (string) variable that can hold a maximum of 10 characters.
String is simply a sequence of characters, so to declare a string, we have to put data type char with string name with square brackets.
Initialization of Strings
Let us take a string:
char name[10]={‘c’, ‘ ’, ‘p’, ‘r’, ‘o’, ‘g’, ‘r’, ‘a’, ‘m’, ‘\0’};
or second method
char name[10]= “c program” ;
Each character is treated as an element of the array name and is stored in the memory as follows:
When the compiler sees a character string, it terminates it with an additional null character means empty. Thus, the element name[9] holds the null character ‘\0’ at the end. When declaring a character array, we must always allow one extra element space for the null terminator.
Program 42 Write a program to input character wise in array and display them.
#include <stdio.h>
int main()
{
char name[10]={'c','','p','r','o','g','r','a','m','\0'};
printf("The given string is : %s",name);
return 0;
}
Program 43 Write a program to input string in array and display them.
#include <stdio.h>
int main()
{
char name[10]="c program";
printf("The given string is : %s",name);
return 0;
}
Array of String
A two dimensional array of characters is called an array of strings. It is also known as a table of strings. It is very useful for solving string sorting problems. In other words, an array of strings can be declared and handled like a two dimensional array.
Syntax:
char string_name[MAX][SIZE]:
As in above syntax, char refers to character data type, string_name is the name of the string variable and in two dimensional array, [MAX] indicates the number of strings and [SIZE] indicates the maximum number characters associated with string.
Example
char name[5][10];
In this example, here is a two dimensional character array. The array is initialized with five character strings with maximum size ten.
Program to demonstrate table of strings
#include <stdio.h>
int main()
{
int i;
char name[5][30]={"Dipendra","Manisha","Suyog","Ram","Laxman"};
for(i=0;i<5;i++)
{
printf("%s\n",name[i]);
}
return 0;
}
String Handling Functions
The C library supports a large number of string handling functions that can be used to carry out many of the string manipulation. The header file #include<string.h> is used for string manipulation functions. Some of the common string manipulation functions are:
strlen() function
The strlen() function returns the length of a string which takes the string name as an argument.
Syntax:
l=strlen(str);
where, str is the name of string and l is the length of the string, returned by function.
Program 44 Write a program to find the length of a string.
#include <stdio.h>
#include <string.h>
int main()
{
char str[100];
int l;
printf("Enter any string = ");
scanf("%s",str);
l=strlen(str);
printf("Length of string is %d ", l);
return 0;
}
strrev() function
The strrev() function is used to reverse the given string.
Syntax:
strrev(str);
where str is string to be reversed.
Program 45 Write a program to reverse the given string.
#include <stdio.h>
#include<string.h>
int main()
{
char str[100];
printf("Enter any string = ");
scanf("%s",str);
strrev(str);
printf("Reverse of string is %s ",str);
return 0;
}
strcpy() function
The strcpy() function is used to copy one string into another string.
Syntax:
strcpy(destination,source) or
strcpy(strl,str2);
where strl,str2 are two strings.
The content of string str2 is copied on string strl.
Program 46 Write a program to copy one string into another string.
#include <stdio.h>
#include<string.h>
int main()
{
char str1[100],str2[100];
printf("Enter any string = ");
scanf("%s",str1);
strcpy(str2,str1);
printf("After copying the string is %s ", str2);
return 0;
}
strcat() function
The strcat() function is used to join or concatenate one string into another string.
Syntax:
strcat(strl,str2);
where str1,str2 are two strings. The content of string str2 is concatenated with string str1.
Program 47 Write a program to concatenate two strings into one string.
#include <stdio.h>
#include<string.h>
int main()
{
char str1[100],str2[100];
printf("Enter two strings = ");
scanf("%s%s",str1,str2);
strcat(str1,str2);
printf("After copying the string is %s ", str1);
return 0;
}
strcmp( ) function
The strcmp() function is used to compare two strings, character by character and stops comparison when there is a difference in the ASCII value or the end of any one string and returns ASCII difference of the character that is integer.
Syntax:
v=strcmp(strl,str2);
Where, str1 and str2 are two strings to be compared and v is a value returned by the function which is either zero(equal), positive value(descending) or negative value(ascending).
Program 48 Write a program to compare two strings
#include <stdio.h>
#include<string.h>
int main()
{
char str1[50],str2[50];
printf("Enter two strings : ");
scanf("%s%s",str1,str2);
int v=strcmp(str1,str2);
if(v==0)
printf("Both strings are same and have same ASCII value");
else if(v>0)
printf("%s comes after %s or %s has more ASCII value than %s",str1,str2,str1,str2);
else
printf("%s comes before %s or %s has more ASCII value than %s",str2,str1,str2,str1);
return 0;
}
strlwr() function
The strlwr() function is used to convert upper case characters of string into lower case characters.
Syntax:
strlwr (str);
where str is string to be converted into lower case characters.
Program 49 Write a program to convert the given string into lower case.
#include <stdio.h>
#include<string.h>
int main()
{
char str[50];
printf("Enter a string : ");
scanf("%s",str);
strlwr(str);
printf("Given string in lower case is %s ",str);
return 0;
}
strupr() function
The strupr() function is used to convert lower case characters of string into upper case characters.
Syntax:
strupr (str);
where str is string to be converted into upper case characters.
Program 50 Write a program to input string in array and display them.
#include <stdio.h>
#include<string.h>
int main()
{
char str[50];
printf("Enter a string : ");
scanf("%s",str);
strupr(str);
printf("Given string in upper case is %s ",str);
return 0;
}
Worked Out Examples
Program 51 Write a program to find the length of the given string without using built in function.
#include <stdio.h>
#include<string.h>
int main()
{
char str[50];
int i,length=0;
printf("Enter a string : ");
scanf("%s",str);
for(i=0;str[i]!='\0';i++)// no body so use semicolon
{
length++;
}
printf("Length of string is %d",length);
return 0;
}
Program 52 Write a program to input strings and sort them.
#include<stdio.h>
#include<string.h>
int main()
{
char string[100][100],temp[100];
int i,j,n;
printf("enter n as total strings\n");
scanf("%d",&n);
printf("enter strings\n");
for(i=0;i<n;i++)
{
printf(" string for location %d = ",i);
scanf("%s",string[i]);
}
for(i=0;i<n;i++)
{
for(j=i+1;j<n;j++)
{
if(strcmp(string[i],string[j])>0)
{
strcpy(temp,string[i]);
strcpy(string[i],string[j]);
strcpy(string[j],temp);
}
}
}
printf("sorted strings are\n");
for(i=0;i<n;i++)
{
printf("name =%s \n",string[i]);
}
return 0;
}
