How to use the command 'c99' (with examples)

The c99 command is an integral tool for developers working with C programming. It adheres to the ISO C standard, allowing programmers to compile C source code efficiently. With c99, you can transform human-readable C code into an executable program, which is essential for testing and running applications. This command supports various options to customize the compilation process, making it versatile for different stages of software development.

Use case 1: Compile source file(s) and create an executable

Code:

c99 file.c

Motivation:

Compiling a C source file into an executable is often the first step in running a C program. This simple command allows developers to check their logic and ensure that the program runs as expected. It’s especially valuable during the early stages of development when a developer wants quick feedback on basic functionality and logic checks of their code.

Explanation:

• c99: This signifies using the C compiler that conforms to the ISO C standard.
• file.c: This is the source file that contains the C code you want to compile into an executable. The extension .c indicates it’s a C source file.

Example Output:

Upon successful compilation, an executable named a.out is usually created in the current directory. If there are no syntax errors, there will be no output message indicating success, following Unix convention.

Use case 2: Compile source file(s) and specify the executable [o]utput filename

Code:

c99 -o executable_name file.c

Motivation:

Specifying an output filename during compilation is crucial for managing different builds and maintaining organized code environments. It helps developers easily identify what each compiled file represents, facilitating multiple program versions or modular code structures without defaulting to the typical a.out.

Explanation:

• c99: Again indicating the use of the ISO C standard compiler.
• -o executable_name: The -o flag stands for “output” and allows the user to specify the name of the file to be generated.
• file.c: The C source file to be compiled into the executable.

Example Output:

The result is an executable file named executable_name. No message will be displayed if the compilation is successful. However, errors in the source file will result in warning or error messages being displayed.

Use case 3: Compile source file(s) and create object file(s)

Code:

c99 -c file.c

Motivation:

Creating object files is a key part of modular programming, enabling developers to compile parts of a larger program piecemeal. This approach is beneficial when working on large projects where recompiling the entire source code for every change would be inefficient.

Explanation:

• c99: To use the ISO C standard for compilation.
• -c: This flag tells the compiler to generate object files (.o files) from the provided source code without linking them into an executable.
• file.c: The source code file to compile into an object file.

Example Output:

This command produces an object file named file.o. Object files are intermediary products of compilation, waiting to be linked with other object files or libraries to form an executable.

Use case 4: Compile source file(s), link with object file(s), and create an executable

Code:

c99 file.c file.o

Motivation:

Linking source files with object files is a critical step in creating complete programs from separate modules or libraries. It allows developers to combine various components, facilitating reuse of code blocks and efficient division of labor in development teams.

Explanation:

• c99: Selects the ISO C standard compiler.
• file.c: The new source code file to be compiled and linked.
• file.o: An already compiled object file to be incorporated within the linking process.

Example Output:

Running this command generates an executable, commonly named a.out. This executable is the linked result of the file.c source code and the pre-existing functionalities in file.o.

Conclusion

The c99 command provides developers with a versatile set of options for compiling C programs, whether focusing on quick testing, producing organized executables, or building complex applications from modular components. Understanding these use cases ensures that C developers can efficiently manage their projects and adapt to different development needs.