# How to reverse a C string

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In this example we delve into a straightforward function designed to reverse a C-string. As we traverse the theoretical realm, it’s crucial to understand that a C string is essentially a character array culminating with the distinctive termination character ‘\0’ at the end of the actual string. To grasp the intricacies, consider that the length of the array housing the actual string should, at most, be one less than the array’s total length, as the final spot is reserved for the termination character. This concept underscores the delicate balance required when manipulating C-strings to ensure seamless operations within the defined boundaries.

For example

``````char array[10];

Position : 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9
Values   :\0   _   _   _   _   _   _   _   _   _

Position : 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9
Values   : H   E   L   L   O  \0   _   _   _   _``````
``````#include <string.h>
#include <stdio.h>
#include <stdlib.h>

void str_reverse(char* arg)
{
if (arg == NULL)
return;

if (strlen(arg) == 0 || strlen(arg)==1)
return;

for (int i = 0; i < (strlen(arg))/2; i++)
{
char t = arg[i];
arg[i] = arg[(strlen(arg)-1) - i];
arg[(strlen(arg) - 1) - i] = t;
}
}

/// Example for Testing the function

int main()
{
char test0[] = "";
char test1[] = "1";
char test2[] = "12";
char test3[] = "123";
char test4[] = "1234";
char test5[] = "12345";

str_reverse(test0);
str_reverse(test1);
str_reverse(test2);
str_reverse(test3);
str_reverse(test4);
str_reverse(test5);

return 0;
}``````
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• Ahmed says:

Please do a tutorial to convert string to uppercase.

• Annie S. says:

Thx for the quick but to the point explanation!

• Haniya says:

Thank you sir!