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Overview of C Language 1 First Program in C Hello World 2 Basic Structure of C Programming 3 Tokens in C 4 Keywords in C 5 Identifiers in C 6 Format Specifiers 7 Format Specifiers Examples 8 History of C

C Programming Language MCQ 1 Overview Of C Language 2 Fundamentals of C Language 3 Data Types in C Language 4 Variable in C Language 5 Constant in C Language 6 Operators and Enums in C Language 7 String in C Language 8 Decision Making of C Language 9 C Language Loop Control 10 Function in C Language 11 Structure in C Language 12 Union in C Language 13 File Input/Output in C Language 14 Array in C Language 15 Pointer in C Language 16 C Language Pre-Processor 17 Dynamic Memory Allocation in C Language

Data Types in C Language 1 int Data Type in C 2 float Data Type in C 3 double Data Type in C 4 char Data Type in C

Variable in C Language 1 Variable Introduction in C 2 Variable Declaration and Initialization 3 Variable types and Scope in C 4 Local Variable in C 5 static Variable in C 6 Global variables in C 7 Storage Class in C

Constant in C Language 1 Constants in C

Operators and Enums in C Language 1 Introduction to Operator in C 2 Arithmetic Operators in C 3 Relational Operators in C 4 Bit-wise Operators in C 5 Logical Operators in C 6 Assignment Operators in C 7 Conditional Operator in C 8 sizeof() Operator in C 9 Operator Precedance in C language 10 ASCII Value

Decision Making of C Language 1 Decision Making in C Introduction 2 if Statement 3 if-else Statement 4 Nested if Statement 5 if else if Ladder 6 switch case in C

Loop control in C Language 1 Loop Introduction in C Language 2 While Loop in C Language 3 Do While Loop in C Language 4 For Loop in C Language

Control Flow in C Programming 1 break Statement in C 2 continue Statement in C 3 goto Statement in C

Array in C Language 1 Single Dimensional Array 2 Multi-Dimensional Array in C

String in C Language 1 Introduction to String

Function in C Language 1 Function in C 2 Function Calling in C 3 return type in Function 4 Call by Value in C 5 User Define Function 6 Predefined Functions

String functions in C 1 All String Functions 2 strcat() function 3 strncat() function 4 strcpy() function 5 strncpy() function 6 strlen() function 7 strcmp() function 8 strcmpi() function 9 strchr() function 10 strrchr() function 11 strstr() function 12 strrstr() function 13 strdup() function 14 strlwr() function 15 strupr() function 16 strrev() function 17 strset() function 18 strnset() function 19 strtok() function

Recursion in c 1 Introduction to Recursion 2 Direct and Indirect Recursion

Pointer in C Language 1 Pointer in C 2 types of pointer 3 NULL pointer 4 Dangling Pointer 5 Void/Generic Pointers 6 Wild Pointer 7 Near, Far and Huge Pointer 8 Pointer Expressions and Arithmetic 9 Pointer and Array 10 Strings as pointers 11 Pointer to Function 12 Call by Reference in C

Structure in C Language 1 Structure in C 2 Nested Structure in C 3 Array of Structures in C 4 Pointer to Structure 5 Structure to Function in C 6 typedef in C 7 typedef vs #define in C

Union in C Language 1 Union in C

File Input/Output 1 Introduction to File 2 File Operation in c

Dynamic Memory Allocation 1 Introduction to DMA 2 calloc() and free() 3 realloc() and free() function

C Pre-processor 1 Introduction about Pre-processor

Command Line Arguments 1 Introduction CLAs

C Programming Language 1 Important points about C 2 Why Use C 3 Applications of C 4 C Language and English Language 5 Features of C 6 C, C++ and Java 7 About C tutorial

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strncat() Function in C: Concatenating Strings Safely

Rumman Ansari July 05, 2024 10,091 views

strncat() Function in C: Concatenating Strings Safely

strncat( ) function in C language concatenates (appends) portion of one string at the end of another string. Syntax for strncat( ) function is given below.

Syntax

char *strncat(char *strng1, const char *strng2, size_t count);

Method	Description
`strncat ( strng2, strng1, 3 );`	First 3 characters of strng1 is concatenated at the end of strng2.
`strncat ( strng1, strng2, 3 );`	First 3 characters of strng2 is concatenated at the end of strng1.

Parameters

The strncat( ) function concatenates not more than count characters of the string pointed to by strng2 to the string pointed to by strng1 and terminates strng1 with a null. The null terminator originally ending strng1 is overwritten by the first character of strng2. The string strng2 is untouched by the operation. If the strings overlap, the behavior is undefined.

In C99, strng1 and strng2 are qualified by restrict. The strncat( ) function returns strng1.

Remember that no bounds checking takes place, so it is the programmer's responsibility to ensure that strng1 is large enough to hold both its original contents and also those of strng2.

Program 1

#include 
#include 
int main(void)
{
	char s1[80], s2[80];
	unsigned int len;
	gets(s1);
	gets(s2);
	/* compute how many chars will actually fit */
	len = 79 - strlen(s2);
	strncat(s2, s1, len);
	printf(s2);
	return 0;
}

Output

Hello
Hi
Hi HelloPress any key to continue . . .

Program 2

#include 
#include 
int main( )
{
   char source[ ] = "Welcome" ;
   char target[ ]= "C tutorial" ;
 
   printf ( "\nSource string = %s", source ) ;
   printf ( "\nTarget string = %s", target ) ;
 
   strncat ( target, source, 5 ) ;
 
   printf ( "\nTarget string after strncat( ) = %s", target ) ;
}

Output

In this program, first 5 characters of the string "Welcome" is concatenated at the end of the string "C tutorial" using strncat( ) function and result is displayed as "C tutorial Welco".

Source string = Welcome
Target string = C tutorial
Target string after strncat( ) = C tutorialWelco