char temp1[4] = "abc";
char *temp2 = "123";
strcpy(temp1,temp2);
if I want to copy a string literal to an array, it works well, but if I do it in the opposite way, I get an error:
char temp1[4] = "abc";
char *temp2 = "123";
strcpy(temp2,temp1);
The feedback from compiler is "Segmentation fault".
So what's the differences? Is there anyway to copy a string to a string literal?
Thx.
You need to understand the subtle difference between these 2 lines
char temp1[4] = "abc";
char *temp2 = "123";
The first one creates a 4 character variable and copies "abc\0" to it.
You can overwrite that if you want to. You can do e.g. temp1[0] = 'x' if you want.
The second one creates a pointer that points to the constant literal "123\0".
You cannot overwrite that, its typically in memory that is declared read only to the OS.
What you have is more complicated than a string literal and what you attempt to do cannot be described as "copying to string literal". Which is good, because copying to a string literal is literally impossible. (Excuse the pun.)
First, what you are successfully doing in the first code quote is copying from a string literal into an array of chars of size 4 (you knew that). You are however doing this with the added detail of copying via a pointer to that string literal (temp2). Also note that what the pointer is pointing to is not a variable which can be edited in any way. It is "just a string which the linker knows about".
In the second code quote you attempt to copy a string (strictly speaking a zero-terminated sequence of chars which is stored in an array, temp1, but not a string literal) to a place where a pointer to char (temp2) points to, but which happens not to be a variable which is legal to write to.
The types of the involved variables allow such an operation basically, but in this case it is forbidden/impossible; which causes the segmentation fault.
Now what IS possible and might be what you actually attempt, is to repoint temp2 to the address at the beginning of temp1. I believe that is what gives you the desired effect:
char temp1[4] = "abc";
char *temp2 = "123";
/* Some code, in which temp2 is used with a meaningful
initialisation value, which is represented by "123".
Then, I assume you want to change the pointer, so that it points
to a dynamically determined string, which is stored in a changeable
variable.
To do that: */
temp2=temp1;
/* But make sure to keep the variable, the name you chose makes me worry. */
Note that an array identifier can be used as a pointer to the type of the array entries.
