strncpy() function in C Language

• strncpy( ) function copies portion of contents of one string into another string. Syntax for strncpy( ) function is given below.

char * strncpy ( char * destination, const char * source, size_t num );

• Example:

strncpy ( str1, str2, 4) – It copies first 4 characters of str2 into str1.
strncpy ( str2, str1, 4) – It copies first 4 characters of str1 into str2.

• If destination string length is less than source string, entire source string value won’t be copied into destination string.
• For example, consider destination string length is 20 and source string length is 30.
• If you want to copy 25 characters from source string using strncpy( ) function, only 20 characters from source string will be copied into destination string and remaining 5 characters won’t be copied and will be truncated.

Example program for strncpy( ) function in C Language:

• In this program, only 5 characters from source string “fresh2refresh” is copied into target string using strncpy( ) function.

C

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#include <stdio.h> #include <string.h> int main( ) {    char source[ ] = "fresh2refresh" ;    char target[20]= "" ;    printf ( "\nsource string = %s", source ) ;    printf ( "\ntarget string = %s", target ) ;    strncpy ( target, source, 5 ) ;    printf ( "\ntarget string after strcpy( ) = %s", target ) ;    return 0; }

Output:

source string = fresh2refresh target string = target string after strncpy( ) = fresh

Other String functions in C Language:

• String.h header file supports all the string functions in C language. All the string functions are given below.

S.no	String functions	Description
1	strcat ( )	Concatenates str2 at the end of str1.
2	strncat ( )	appends a portion of string to another
3	strcpy ( )	Copies str2 into str1
4	strncpy.(.)	copies given number of characters of one string to another
5	strlen ( )	gives the length of str1.
6	strcmp ( )	Returns 0 if str1 is same as str2. Returns <0 if strl < str2. Returns >0 if str1 > str2.
7	strcmpi ( )	Same as strcmp() function. But, this function negotiates case.  “A” and “a” are treated as same.
8	strchr ( )	Returns pointer to first occurrence of char in str1.
9	strrchr ( )	last occurrence of given character in a string is found
10	strstr ( )	Returns pointer to first occurrence of str2 in str1.
11	strrstr ( )	Returns pointer to last occurrence of str2 in str1.
12	strdup ( )	duplicates the string
13	strlwr ( )	converts string to lowercase
14	strupr ( )	converts string to uppercase
15	strrev ( )	reverses the given string
16	strset ( )	sets all character in a string to given character
17	strnset ( )	It sets the portion of characters in a string to given character
18	strtok ( )	tokenizing given string using delimiter

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