How to Compile a C Program from Command Line Quickly

To compile a C program from the command line, use the gcc compiler with the syntax gcc source.c -o output. This command compiles source.c into an executable named output.

Syntax

The basic command to compile a C program is:

• gcc: The GNU C Compiler command.
• source.c: Your C source file.
• -o output: Optional flag to name the output executable output. If omitted, the default executable is a.out.

bash

gcc source.c -o output

Example

This example shows how to compile and run a simple C program that prints "Hello, World!".

c

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

Output

Hello, World!

Common Pitfalls

Common mistakes when compiling C programs include:

• Forgetting to save the source file before compiling.
• Not specifying the correct file name or path.
• Omitting the -o option and expecting a specific executable name.
• Trying to run the source file directly without compiling.

bash

/* Wrong: Trying to run source file directly */
./source.c

/* Right: Compile then run */
gcc source.c -o program
./program

Quick Reference

Command	Description
gcc source.c	Compile source.c to default executable a.out
gcc source.c -o myprog	Compile source.c to executable named myprog
./a.out	Run default executable
./myprog	Run named executable
gcc -Wall source.c -o prog	Compile with all warnings enabled

Key Takeaways

Use gcc source.c -o output to compile and name your executable.

Always save your source file before compiling to avoid errors.

Run the compiled executable, not the source file.

Use -Wall flag to see helpful warnings during compilation.

If -o is omitted, the executable is named a.out by default.