C – String Library Functions

strlen() :

• strlen() returns length of string excluding null character.
• Return type is size_t (positive integer)
  • Prototype is   size_t  strlen(char s[]);

#include<string.h> int main() {             char str[20];             size_t len;             printf(“Enter string : “);             gets(str);             len = strlen(str);             printf(“Length is : %u \n”, len);             return 0; }

Program to find the length of String without using library function:

int main() {             char str[20];             size_t len=0, i=0;             printf(“Enter string : “);             gets(str);             while(str[i] != ‘\0’){                         len++;                         i++;             }             printf(“Length is : %u \n”, len);             return 0; }

Program to convert Upper case characters into Lower case in String:

#include<string.h> int main() {             char src[20];             printf(“Enter Upper string : “);             gets(src);             strlwr(src);                    printf(“Lower string : %s \n”, src);             return 0; }

Program to convert Upper case characters into Lower case without Library function:

#include<stdio.h> #include<string.h> int main() {             char src[20];             int i=0;             printf(“Enter Upper string : “);             gets(src);               while(src[i] != ‘\0’)             {                         if(src[i]>=’A’ && src[i]<=’Z’)                         {                                     src[i] = src[i]+32;                         }                         i++;             }             printf(“Lower string : %s \n”, src); }

Program to reverse the given string in C:

#include<string.h> int main() {             char src[20];             printf(“Enter string : “);             gets(src);             strrev(src);                    printf(“Reverse string : %s \n”, src); }

Program to reverse the String without using Library function:

#include<string.h> int main() {             char src[20], temp;             int i, j;                         printf(“Enter string : “);             gets(src);               i=0;             j=strlen(src)-1;             while(i<j)             {                         temp = src[i];                         src[i] = src[j];                         src[j] = temp;                         i++;                         j–;             }             printf(“Reverse string : %s \n”, src); }