How to print a variable name in C?

In C programming, you can print the name of a variable as a string using the stringizing operator (#) within a macro. This technique is useful for debugging and logging purposes where you want to display variable names along with their values.

Syntax

#define MACRO_NAME(variable) #variable

The # operator converts the macro parameter into a string literal.

Example

Here's how to create a macro that prints variable names −

#include <stdio.h>
#define VariableName(name) #name

int main() {
    int age = 25;
    char grade = 'A';
    float salary = 50000.75;
    
    printf("The variable name: %s
", VariableName(age));
    printf("The variable name: %s
", VariableName(grade));
    printf("The variable name: %s
", VariableName(salary));
    
    return 0;
}

The variable name: age
The variable name: grade
The variable name: salary

Enhanced Example: Print Variable Name and Value

You can combine variable names with their values for better debugging −

#include <stdio.h>
#define PRINT_VAR(var) printf("%s = %d
", #var, var)
#define PRINT_CHAR(var) printf("%s = %c
", #var, var)
#define PRINT_FLOAT(var) printf("%s = %.2f
", #var, var)

int main() {
    int count = 10;
    char letter = 'X';
    float price = 99.99;
    
    PRINT_VAR(count);
    PRINT_CHAR(letter);
    PRINT_FLOAT(price);
    
    return 0;
}

count = 10
letter = X
price = 99.99

How It Works

• The # operator (stringizing operator) converts the macro argument into a string literal
• When you call VariableName(age), it expands to "age"
• This happens during preprocessing, before compilation
• The macro works with any valid identifier name

Conclusion

Using the stringizing operator with macros is an effective way to print variable names in C. This technique is particularly valuable for creating debugging utilities and logging functions that display both variable names and their values.