Cannot output the C struct char array member [duplicate] - c

Question

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How can I correctly assign a new string value?
(4 answers)
Closed 1 year ago.
I'm learning how to use structures in C. But in the following code I couldn't print myArray "HELLO!" which is declared as a char array:
#include <stdio.h>
struct myStruct
{
int myInt;
float myFloat;
char myArray[40];
};
int main()
{
struct myStruct p1;
p1.myInt = 80;
p1.myFloat = 3.14;
printf("Integer: %d\n", p1.myInt);
printf("Float: %f\n", p1.myFloat);
p1.myArray = "HELLO!";
printf("Array: %s\n", p1.myArray);
return 0;
}
What is wrong in the above syntax that I don't get "HELLO!" as an output? Something wrong here:
p1.myArray = "HELLO!";
printf("Array: %s\n", p1.myArray);

Answer 1

Arrays are non-modifiable lvalues. So this attempt to assign a pointer (the string literal is implicitly converted to a pointer to its first element) to an array designator
p1.myArray = "HELLO!";
will not compile.
Either use the standard string function strcpy as for example
#include <string.h>
//...
strcpy( p1.myArray, "HELLO!" );
Or you could initialize the data member initially when the object of the structure type is defined as for example
struct myStruct p1 = { .myInt = 80, .myFloat = 3.14, .myArray = "HELLO!" };
or
struct myStruct p1 = { .myInt = 80, .myFloat = 3.14, .myArray = { "HELLO!" } };
or
struct myStruct p1 = { 80, 3.14, "HELLO!" };
or
struct myStruct p1 = { 80, 3.14, { "HELLO!" } };
Here is a demonstrative program.
#include <stdio.h>
#include <string.h>
struct myStruct
{
int myInt;
float myFloat;
char myArray[40];
};
int main( void )
{
struct myStruct p1 = { .myInt = 80, .myFloat = 3.14, .myArray = { "HELLO!" } };
printf("Integer: %d\n", p1.myInt);
printf("Float: %f\n", p1.myFloat);
printf("Array: %s\n", p1.myArray);
strcpy( p1.myArray, "BYE!" );
printf("\nArray: %s\n", p1.myArray);
return 0;
}
The program output is
Integer: 80
Float: 3.140000
Array: HELLO!
Array: BYE!