Shulou(Shulou.com)06/02 Report--

1. Preface: my understanding of linux environment

For beginners to learn embedded linux, it is very important to understand and operate the whole environment. Programming is usually carried out in the integrated development environment, such as VC6.0, after writing the code, directly click the button "compile", click "run", are interface operations. But have you developers ever thought about how to "compile" and "run" this integrated development environment? What kind of process is it? The integrated development environment is really convenient, accomplishing the desired operation directly through the click of the button, but hides the inherent running logic.

And linux development, you can make your vision more in-depth, the whole process does not have an integrated development environment, edit their own code, write their own compilation process, to run, no longer through the button can be completed, your development process is an integrated environment. Therefore, under the development of linux, you can have a deeper understanding of the internal mechanism of development to run.

Next, the author will learn the first step of embedded Linux learning with you-be familiar with the linux development environment and output my first hello word!

two。 Understand the compilation process

Commonly referred to as "compilation", the process of compilation is as follows:

C program source file (.c)-preprocessing-"(.i file)-compilation -" assembly file (.s)-assembly file (.o)-link-"(executable file)

Executable files can be run directly. For embedded Linux development, executable files also need to be converted to binary files (.bin) before they can be written to the controller. The following is developed for this process and output under Linux:

Start

Myhello word!

2. C program source file editing environment: Windows editor: Source Insight

Write source programs, no matter what system, as long as in any code editor, can be written. Here it is more convenient to write code in Windows's Source Insight editor.

Create a myhello.c source file

Code the myhello.c source file and save it. Main is the function entry. To learn more about the relationship between compiled files, add the HelloFunction () function call, and then create a header file and source file to declare and define the HelloFunction () function.

# include "stdio.h" # include "HelloPrint.h" int main () {printf ("start\ n"); HelloFunction (); return 0;}

3. Similarly, create a HelloPrint.c source file to define the HelloFunction () function.

# include "stdio.h" # include "HelloPrint.h" void HelloFunction () {printf ("myhello word!\ n");}

4. Similarly, create a HelloPrint header file, HelloPrint.h, to declare the HelloFunction () function.

# ifndef _ _ HelloPrint_H#define _ HelloPrint_Hvoid HelloFunction (void); # endif2. Write your own compilation process-makefile file

The makefile file is a collection file of the whole compilation process. The compilation process of the program source file is written into the makefile file in advance. As long as the make command is entered under the command line, the system automatically executes the contents of the makefile file, which is convenient for operation. At the same time, makefile automatically depends on whether the target file is changed, depends on whether the file is updated, and chooses whether to compile or not, so that for a large number of program files, the compilation time can be reduced. Makefile documents are written in the form of specific rules, and there are a lot of information about this on the Internet.

The contents of the makefile file are as follows. The hello file is the executable file to be generated finally, myhello.c and HelloPrint.c are the compilation raw materials, and the gcc compilation tool is used.

Hello: myhello.c HelloPrint.c gcc-o hello myhello.c HelloPrint.cclean: compile and run under rm hello3.linux

The above code is written under Windows, of course, it can also be written under Linux, but it is more convenient to write under Windows. After writing the above code and makefile file, you need to upload it to the linux of the virtual machine.

Upload tool: CuteFTP (you can also use the VMware tools tool in the virtual machine to pull files) SSH remote login tool: SecureCRT (log in to the linux server, you can complete the command line operation in the SecureCRT software under Windows), or you can directly operate the command line in the terminal of linux.

The following files are uploaded and copied to Linux by CuteFTP:

SecureCRT login to the virtual machine linux server interface is as follows, and complete the relevant instructions. And the compilation result after operation is as follows:

You can see that after the make directive, the related files listed are more than the executable file hello, which is the last thing you want. After the hello is executed, the execution result can appear. The output of the first hello word appears. Make clean is used to execute clean content in makefile and delete executable files.

Are the folks here familiar with the linux development environment? Familiarity with the environment is important for getting started with development. These are also the basis of embedded linux development, but the program has not been burned into the controller, so the next article will learn the basic development process through simple S3C2440 bare-board program development.

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