C Library - <string.h>
Last Updated :
15 Mar, 2023
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string.h is a standard header file in the C language that contains functions for manipulating strings (arrays of characters). <string.h> header file contains some useful string functions that can be directly used in a program by invoking the #include preprocessor directive.
Syntax:
#include <string.h>
Example:
// C program to demonstrate the use of C string.h
//header file
#include <stdio.h>
#include <string.h>
int main()
{
// initializing some strings
char str1[20] = "Geeksfor";
char str2[20] = "Geeks";
// using strlen(), strcat()
printf("Str1: %s\n", str1);
printf("Length of Str1 before concatenation: %d\n",
strlen(str1));
strcat(str1, str2); // concatenating str1 and str2
printf("Str1: %s\n", str1);
return 0;
}
Output
Str1: Geeksfor Length of Str1 before concatenation: 8 Str1: GeeksforGeeks
C string.h Library Functions
<string.h> header file contains the following functions:
Function Name | Function Description |
|---|---|
| Returns the length of the string. | |
| Copy one string to another. | |
strncpy() | Copy first n characters of one string to another. |
| Concatenates two strings. | |
| Concatenates first n characters of one string to another. | |
| Compares two strings. | |
strncmp() | Compares first n characters of two strings. |
strchr() | Find the first occurrence of the given character in the string. |
strrchr() | Finds the last occurrence of the given characters in the string. |
| Find the given substring in the string. | |
| Returns the span of the source string not containing any character of the given string. | |
| Returns the span of the source string containing only the characters of the given string. | |
| Finds the first occurrence of any of the characters of the given string in the source string. | |
strtok() | Split the given string into tokens based on some character as a delimiter. |
strcoll() | Compares two strings that are passed. |
| Initialize a block of memory with the given character. | |
memcmp() | Compares two blocks of memory. |
| Copy two blocks of memory. | |
| Moves two blocks of memory. | |
memchr() | Finds the given character in the block of memory. |
Example:
// C program to demonstrate the use of different functions
// of string.h library
#include <stdio.h>
#include <string.h>
// defining the common size of the string arrays
#define size 50
int main()
{
char destString[size] = "Geeksfor";
char sourceString[size] = "Geeks";
char tempDestString[size];
printf("Length of Destination String: %d\n",
strlen(destString));
// copying sourceString to tempDestString using strcpy()
strcpy(tempDestString, sourceString);
printf("tempDestString after strcpy(): %s\n",
tempDestString);
// concatenating source to destination using strcat()
strcat(destString, sourceString);
printf("destString after Concatenation: %s\n",
destString);
// comparison using strcmp()
printf("Comparing destString with sourceString: %d\n",
strcmp(destString, sourceString));
printf("Comparing first 5 characters: %d\n",
strncmp(destString, sourceString, 5));
// searching substring using strstr()
printf("Searching sourceString in destString: %s\n",
strstr(destString, sourceString));
return 0;
}
Output
Length of Destination String: 8 tempDestString after strcpy(): Geeks destString after Concatenation: GeeksforGeeks Comparing destString with sourceString: 102 Comparing first 5 characters: 0 Searching sourceString in destString: GeeksforGeeks
