You need to compare, not assign:
if (strcmp("hello", "hello") == 0)
^
Because you want to check if the result of strcmp("hello", "hello")
equals to 0
.
About the error:
lvalue required as left operand of assignment
lvalue
means an assignable value (variable), and in assignment the left value to the =
has to be lvalue
(pretty clear).
Both function results and constants are not assignable (rvalue
s), so they are rvalue
s. so the order doesn't matter and if you forget to use ==
you will get this error. (edit:)I consider it a good practice in comparison to put the constant in the left side, so if you write =
instead of ==
, you will get a compilation error. for example:
int a = 5;
if (a = 0) // Always evaluated as false, no error.
{
//...
}
vs.
int a = 5;
if (0 = a) // Generates compilation error, you cannot assign a to 0 (rvalue)
{
//...
}
(see first answer to this question: https://stackoverflow.com/questions/2349378/new-programming-jargon-you-coined)