String functions in C++

Unlike single character constants a string constant cannot be assigned directly with a string variable nor compared with an another string.

String functions whose header file is <string.h> have to be used to carry out operation such as comparision, concatenation (combining two strings), assignment operators etc. Some functions are listed below.

strcpy():- This function copies the contents of source string into destination string. Its syntax is

                strcpy(destination string, source string);

Example:

   char sd[10], ss[10]={ “Hi welcome”};

   strcpy(sd,ss);

   cout<<sd;

Output:

   Hi welcome

Thus sd=ss; is invalid statement as arithmetic operation can’t be used two string variable.

strlen():- This function provides the length of the string excluding null character.

Example:

   char ss[10]={ “Welcome”};

   int a= strlen(ss);

   cout<<a;

Output:

   7

The function strlen() counts no of characters used in a string by ignoring null character while the operator sizeof() counts total space allocated if the size is specified with the array name or it counts no of characters including the null characters.

strlen() needs a header file because it is a function whereas sizeof() does not require a header file because it is an operator.

strcat():- This function concatenates(combines) the given strings. Its syntax is

        strcat(s1,s2);

It combines the string s1 with s2 and stores the resultant string with s1.

Example:

   char s1[10]= “Kota”;

   char s2[10]= “Junction”;

   strcat(s1,s2);

   cout<<s1;

Output:

   KotaJunction

strcmp():- It is a function which compares two strings and provides the difference in integer form.

Syntax:

strcmp(s1, s2);

if s1>s2 then it returns +ve value.

if s1<s2 then it returns -ve value.

if s1=s2 then it returns zero.

Example:

1.  s1= “BAT”;

     s2= “CAT”;

     strcmp(s1,s2)=-1

2.  s1= “ARUN”;

     s2= “arun”;

     strcmp(s1,s2)=-32

3.  s1= “Nirmal”;

     s2= “Niranjan”;

     strcmpi(s1,s2)=12

This function is case sensitive i.e. it treats uppercase and lower case of same letter as different. The function strcmpi() can be use to treat the lowercase and uppercase of a letter as identical.

Example:

   s1= “ARUN”;

   s2= “arun”;

   strcmpi(s1,s2)=0