Code Style Guide for C Programming

Writing clean and consistent C code is essential for readability, collaboration, and passing style checks. Below are common issues, how to fix them, and examples formatted like a terminal for clarity.

1. Open Braces { Should Be on the Next Line

Error Messages:

• ERROR: that open brace { should be on the next line
• ERROR: open brace ‘{’ following function declarations go on the next line

Incorrect:

int main() {
    // code
}

Correct:

int main()
{
    // code
}

Fix with sed:

find . -path './.git' -prune -o \( -name '*.c' -o -name '*.h' \) -type f -exec sed -i ':a;N;$!ba;s/\)\s*{/)\n{/g' {} +

-–

2. Suspect Code Indent for Conditional Statements

Incorrect:

if (condition) {
    do_something();
}

Correct:

if (condition)
{
    do_something();
}

Fix:

find . -path './.git' -prune -o \( -name '*.c' -o -name '*.h' \) -type f -exec indent -kr -i8 -ts8 -sob {} +

-–

3. Missing a Blank Line After Declarations

Incorrect:

int a;
int b;

Correct:

int a;

int b;

Fix:

find . -path './.git' -prune -o \( -name '*.c' -o -name '*.h' \) -type f -exec sed -i '/;\s*$/G' {} +

-–

4. Trailing Whitespace

Fix:

find . -path './.git' -prune -o \( -name '*.c' -o -name '*.h' \) -type f -exec sed -i 's/[ \t]*$//' {} +

-–

5. Statements Should Start on a Tabstop

Incorrect:

if (condition)
{
    do_something();
}

Correct:

if (condition)
{
    do_something();
}

-–

6. Parentheses Required on Return Statements

Incorrect:

return value;

Correct:

return (value);

Fix:

find . -path './.git' -prune -o \( -name '*.c' -o -name '*.h' \) -type f -exec sed -i 's/return\s\+\([^;]\+\);/return (\1);/' {} +

-–

7. Braces {} Not Needed for Single Statements

Incorrect:

if (condition) {
    do_something();
}

Correct:

if (condition)
    do_something();

-–

8. Missing Function Documentation

Before:

int add(int a, int b)
{
    return (a + b);
}

After:

/**
 * add - Adds two integers.
 * @a: First integer
 * @b: Second integer
 *
 * Return: Sum of a and b
 */
int add(int a, int b)
{
    return (a + b);
}

-–

9. Additional Recommendations

To keep your code clean automatically, consider using tools like clang-format. You can also integrate formatting into your editor to avoid style errors completely.

Consistent formatting isn’t just about passing checks — it makes your code easier to read, debug, and maintain.