Question

In C, how do you use the value of a variable or a field within a struct as the name of a variable or field within a struct to be used in a program?

i.e.:

char variable_name[];

struct_x.value_of_variable_name = 1;
// assuming the variable struct_x.value_of_variable_name is an int

Answer 1

You can’t. Variable names exist only at compile-time.

You could emulate this behaviour manually by creating a lookup table (that maps a string to a pointer, for instance), but there is no language support for this.