GNU Project C and C++ compiler.
The gcc command invokes the GNU C/C++ compiler, which is the most widely used compiler in the open-source community. It is powerful and supports various performance optimizations. GCC can be used to compile programs in languages such as C, C++, Fortran, Java, Objective-C, and Ada, depending on the installed language support.
gcc (options) (parameters)
-o: Specify the name of the output file.
-E: Stop after the preprocessing stage; do not run the compiler proper.
-S: Stop after the stage of compilation proper; do not assemble.
-Wall: Enable all compiler warning messages.
-c: Compile or assemble the source files, but do not link.
-l: Link with a specified library (the library name follows -l).
-I: Add a directory to the list of directories to be searched for header files.
C Source File: Specifies the C language source code file(s).
Common Compilation Options
Assuming the source file is test.c.
Compile and link without options:
gcc test.c
This preprocesses, assembles, compiles, and links test.c into an executable. Since no output file is specified, the default is a.out.
Option -o:
gcc test.c -o test
Preprocesses, assembles, compiles, and links test.c into an executable named test.
Option -E:
gcc -E test.c -o test.i
Preprocesses test.c and outputs the result to test.i.
Option -S:
gcc -S test.i
Compiles the preprocessed file test.i into assembly code in test.s.
Option -c:
gcc -c test.s
Assembles the file test.s into an object file test.o.
Linking without further options:
gcc test.o -o test
Links the object file test.o into the final executable test.
Option -O:
gcc -O1 test.c -o test
Compiles the program with optimization level 1. Levels range from 1 to 3; higher levels provide better optimization but increase compilation time.
Compiling Multiple Source Files
There are two main ways to compile multiple source files (e.g., test.c and testfun.c).
Compile all files together:
gcc testfun.c test.c -o test
Compiles and links both files into a single executable test.
Compile separately and then link:
gcc -c testfun.c # Compiles testfun.c into testfun.o
gcc -c test.c # Compiles test.c into test.o
gcc testfun.o test.o -o test # Links both object files into test
Comparison: The first method requires all files to be recompiled every time. The second method allows you to recompile only the modified files, saving time on large projects.
Link with a dynamic library:
gcc hello.c -lpthread -o hello
Add a custom include path:
gcc hello.c -lpthread -I /lib64/ -o hello