String handling in C

String handling in C

• what is a string?
  
• A string is combination of characters.
• Any set or sequence of characters defined within double quotation symbols is a constant string.
• In c it is required to do some meaningful operations on the strings

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Initializing Strings

The initialization of a string must the following form which is simpler to the one dimension array

char month1[ ]={‘j’,’a’,’n’,’u’,’a’,’r’,’y’};

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The following example shows the use of string:

/*String.c string variable*/ #include < stdio.h > main() { char month[15]; printf (”Enter the string”); gets (month); printf (”The string entered is %s”, month); }

Note:
Character string always terminated by a null character ‘’. A string variable is always declared as an array & is any valid C variable name. The general form of declaration of a string variable is

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Reading Strings from the terminal:

The function scanf with %s format specification is needed to read the character string from the terminal itself. The following example shows how to read strings from the terminals:

char address[15]; scanf(%s,address);

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String operations (string.h)

language recognizes that strings are terminated by null character and is a different class of array by letting us input and output the array as a unit. To array out many of the string manipulations,C library supports a large number of string handling functions that can be used such as:

1. Length (number of characters in the string).

2. Concatentation (adding two are more strings)

3. Comparing two strings.

4. Substring (Extract substring from a given string)

5. Copy(copies one string over another)

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strlen() function:

This function counts and returns the number of characters in a particular string. The length always does not include a null character. The syntax of strlen() is as follows:

n=strlen(string);

Where n is the integer variable which receives the value of length of the string.

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The following program shows to find the length of the string using strlen() function

/*writr a c program to find the length of the string using strlen() function*/ #include < stdio.h > include < string.h > void main() { char name[100]; int length; printf(”Enter the string”); gets(name); length=strlen(name); printf(”\nNumber of characters in the string is=%d”,length); }

strcat() function:

when you combine two strings, you add the characters of one string to the end of the other string. This process is called as concatenation. The strcat() function is used to joins 2 strings together. It takes the following form:

strcat(string1,string2)

string1 & string2 are the character arrays. When the function strcat is executed string2 is appended to the string1. the string at string2 always remains unchanged.

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strcmp function:

In c,you cannot directly compare the value of 2 strings in a condition like if(string1==string2) Most libraries however contain the function called strcmp(),which returns a zero if 2 strings are equal, or a non zero number if the strings are not the same. The syntax of strcmp() is given below:

Strcmp(string1,string2)

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strcmpi() function

This function is same as strcmp() which compares 2 strings but not case sensitive.

Strcmp(string1,string2)

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strcpy() function:

To assign the characters to a string,C does not allow you directly as in the statement name=Robert; Instead use the strcpy() function found in most compilers the syntax of the function is illustrated below.

strcpy(string1,string2);

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strlwr () function:

This function converts all characters in a string from uppercase to lowercase

The syntax of the function strlwr is illustrated below

strlwr(string);

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strrev() function:

This function reverses the characters in a particular string. The syntax of the function strrev is illustrated below

strrev(string);

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write program to print name in reverse

#include < stdio.h >
#include < string.h >
void main()

{

char nm[20];

int i,len=0;

clrscr();

printf("Enter the name :");

gets(nm);

for(i=len;i>=0;i--)

{

printf("%c",nm[i]);

}

getch();

}

Dispay a string in increasing order.
#include < stdio.h >
#include < string.h >

void main()
{
char st[20];
int len=0,i,j;
clrscr();
printf("Enter a string");
gets(st);
len=strlen(st);
for(i=0;i<len;i++)
{
for(j=0;j<i;j++)
{
printf("%c",st[j]);
}
printf("\n");
}
getch();
}

Display the sum of ascii of character;
#include < stdio.h >

#include < string.h >

void main()

{

char st[20]

int i,n,len=0,sum=0;

clrscr();

printf("Enter String");

gets(st);

len=strlen(st);

printf("The sum of ascii of character is : ");

for(i=0;i<len;i++)

{

printf("%d+",st[i]);

sum=sum+st[i];

}

printf("=%d",sum);

getch();

}

Remove duplicate Entry in Array

#include < stdio.h >
#include < string.h >

void main()

{

   int a[10],i,n,j,flag=1;

   clrscr();

   for(i=0;i<10;i++)

     {

      printf("Enter array elements a[%d] :"i);

       scanf("%d",&a[i]);

     }

  for(i=0;i<10;i++)

    {

    flag =1; 

    for(j=0;j<i;j++)

      {

        if(a[i]==a[j])

          {

          flag=0;

          }

     }

        if(flag==1)

         {

        prinf("\n%d",a[i]);

         }

 }

getch(); 

}

The following program illustrate the use of string functions:

/* Example program to use string functions*/
#include < stdio.h >
#include < string.h >
void main()
{
char s1[20],s2[20],s3[20];
int x,l1,l2,l3;
printf(”Enter the strings”);
scanf(”%s%s”,s1,s2);
x=strcmp(s1,s2);
if(x!=0)
{printf(”\nStrings are not equal\n”);
strcat(s1,s2);
}
else
printf(”\nStrings are equal”);
strcpy(s3,s1);
l1=strlen(s1);
l2=strlen(s2);
l3=strlen(s3);
printf(”\ns1=%s\t length=%d characters\n”,s1,l1);
printf(”\ns2=%s\t length=%d characters\n”,s2,l2);
printf(”\ns3=%s\t length=%d characters\n”,s3,l3);
}