C program to Copy String

How to write a C program to copy string without using the strcpy function. We can achieve the same in multiple ways, but we will discuss four different approaches: using For Loop, While Loop, Functions, and Pointers.

C program to Copy String without using strcpy()

This program for string copy allows the user to enter any character array. Next, it will use For Loop to iterate each character in that string and copy them into another character array.

#include <stdio.h>
#include <string.h>
 
int main()
{
  	char Str[100], CopyStr[100];
  	int i;
 
  	printf("\n Please Enter any String :  ");
  	gets(Str);
 
  	for (i = 0; Str[i]!='\0'; i++)
  	{
  		CopyStr[i] = Str[i];
  	}
  	CopyStr[i] = '\0';

  	printf("\n String that we coped into CopyStr = %s", CopyStr);
  	printf("\n Total Number of Characters that we copied = %d\n", i);
  	
  	return 0;
}

Within this program to Copy String program, We declared two character arrays of size 100. The next two statements ask the user to enter any word and assign the user entered char array to the variable. Please refer to the strcpy function.

In the next line, we have For Loop to iterate and copy string,

User Entered = “Good”

First Iteration: for (i = 0; Str[0]!=’\0′; 0++)
condition is TRUE because Str[0] = G
CopyStr[i] = Str[i]
CopyStr[0] = Str[0] = G

Second Iteration: for (i = 1; Str[1]!=’\0′; 1++)
condition is TRUE because Str[1] = o
CopyStr[1] = o

Third Iteration: for (i = 2; Str[2]!=’\0′; 2++)
condition is TRUE because Str[2] = o
CopyStr[2] = o

Fourth Iteration: for (i = 3; Str[3]!=’\0′; 3++)
condition is TRUE because Str[3] = d
CopyStr[3] = d

Fifth Iteration: for (i = 4; Str[4]!=’\0′; 4++)
condition is False. So, it will exit from the For Loop

The Final Programming printf statement will print the message inside a CopyString character array.

printf("\n String that we coped into CopyStr = %s", CopyStr);

Program to Copy String Using While Loop

This program for string copy is the same as above, but this time, we are using a While Loop (Just replacing For Loop with While Loop).

#include <stdio.h>
#include <string.h>
 
int main()
{
  	char Str[100], CopyStr[100];
  	int i = 0;
 
  	printf("\n Please Enter any Sentence :  ");
  	gets(Str);
 
  	while(Str[i]!='\0')
  	{
  		CopyStr[i] = Str[i];
  		i++;
  	}
  	CopyStr[i] = '\0';

  	printf("\n Copied into CopyStr = %s", CopyStr);
  	printf("\n Total Number of Characters that we copied = %d\n", i);
  	
  	return 0;
}

Please Enter any Sentence : Tutorial Gateway

Copied into CopyStr = Tutorial Gateway

Total Number of Characters that we copied = 17

C Program to Copy String Using Functions

This program is the same as above. However, this time, we are using the Functions concept to separate the logic from the main.

#include <stdio.h>
#include <string.h>
void CopyString(char str1[], char str2[], int index);

int main()
{
  	char Str[100], CopyStr[100];
 
  	printf("\n Please Enter any text :  ");
  	gets(Str);
 
	CopyString(Str, CopyStr, 0);
	
	printf("\n Original   = %s", Str);
  	printf("\n Copied into CopyStr = %s", CopyStr);
  	
  	return 0;
}

void CopyString(char str1[], char str2[], int index)
{
	str2[index] = str1[index];
	if(str1[index] == '\0')
	{
		return; 
	}
	CopyString(str1, str2, index + 1);
}

Please Enter any Sentence : C Programming Tutorial

Original = C Programming Tutorial

Copied into CopyStr = C Programming Tutorial

Copy String Using Pointers

This copy program is the same as above, but this time, we are using Pointers to copy one string to another.

#include <stdio.h>
#include <string.h>
void CopyString(char* st1, char* st2);

int main()
{
  	char St[100], CopyStr[100];
 
  	printf("\n Please Enter any Text :  ");
  	gets(St);
 
	CopyString(St, CopyStr);
	
	printf("\n Original   = %s", St);
  	printf("\n Copied into CopyStr = %s", CopyStr);
  	
  	return 0;
}

void CopyString(char* st1, char* st2)
{
	int i = 0;

  	for (i = 0; st1[i]!='\0'; i++)
  	{
  		st2[i] = st1[i];
  	}
	st2[i] = '\0';
}

Please Enter any Sentence : C programs

Original = C programs

Copied into CopyStr = C programs