Linux (/ˈlɪnʊks/ LIN-uuks)is a family of open-source Unix-like operating systems based on the Linux kernel,an operating system kernel first released on September 17, 1991, by Linus Torvalds.
Linux was originally developed for personal computers based on the Intel x86 architecture, but has since been ported to more platforms than any other operating system. Linux is now the leading operating system on servers (over 96.4% of the top 1 million web servers' operating systems are Linux).
So it would be very useful if you know how to develop and run programs on Linux.
On Linux, software development tools are usually cut into independent small tools, each of which handles different problems. Taking C language software development as an example, editors (emacs, vim, etc.) are used to edit programs, debuggers (gdb) are used to debug programs, compilers (GCC) are used to compile and link programs, and performance analysis tools ( gcov, gprof) are used to optimize programs, the document generator (doxygen) is used to generate documents, etc.
In this issue, we will use the most basic Vim editor and Gcc compiler to demonstrate how to perform the most basic software development on Linux. Before officially starting, we must first check whether these softwares exist in the environment and their versions.
Use which command to check whether required tools are existed in your environment.
which gcc
which vim
which tar
If not existed, use the following command to install it
sudo yum install -y gcc vim tar
p.s. if it asks for password, the default password is openEuler12#$
You can use the following command to check whether the required tools has correct version.
gcc --version
vim --version
Let's write our first C program on Linux, yes, the Hello World!
Select your favourite folder and create our working dir:
mkdir {some folder name}
cd {some folder name}
Use vim to write code:
vim hello.c
Hit either a i o or s on your keyboard and entering the edit mode.
Write down the following codes:
#include <stdio.h>
int main(void){
printf("Hello, World!\n");
}
Hit ESC on your keyboard to enter the command mode and enter :wq to save and exit.
When we talk about programs, we usually refers to a program that can be run directly after double-clicking it. Such a program is called an executable program (Executable Program). Under Windows, the suffixes of executable programs are .exe and .com (where .exe More common); Under UNIX-like systems (Linux, Mac OS, etc.), executable programs do not have a specific suffix, and the system determines whether it is an executable program based on the header information of the file.
The interior of an executable program is a collection of computer instructions and data. They are all in binary form and can be directly recognized by the CPU without any obstacles; but for programmers, they are very obscure and difficult to remember and use. Therefore, programs such as ours were born. High-level programming languages such as the C language program you just wrote.
But for the CPU, the C language code is a bible, which is not recognized at all. The CPU only recognizes a few hundred instructions in binary form. This requires a tool to convert the C language code into binary instructions that the CPU can recognize, that is, to process the code into an executable program; this tool is a special software called a compiler.
GCC developed by the GUN organization is commonly used under Linux, and Linux distributions usually come with GCC.
In this step we will use gcc command to compile our code:
gcc hello.c -o hello
Checkout what we have built:
ls -l
Run our code:
./hello
In most cases, our codes are far more complicated, we could have one function callling functions from other file. In this step, we will see how to build a more complicated application.
We have some codes for you, download them using the following command:
curl -L https://github.com/openeuler-mirror/openEulerCodeHeat/raw/main/Advanced-Issues/awsome_codes.tar.gz
The codes are packed as tarball(*.tar) and zipped using gzip(*.gz), this is quite common in the Linux and open source world, let's unzip and untar them:
tar -zxvf awsome_codes && cd awsome_codes
Checkout what we got with ls -l, it should be like this:
ls -l
-rw-r--r-- 1 root root 189 11 23 03:38 cos_value.c
-rw-r--r-- 1 root root 80 11 23 03:34 cos_value.h
-rw-r--r-- 1 root root 106 2 11 2022 hello.c
-rw-r--r-- 1 root root 404 11 23 03:36 main.c
-rw-r--r-- 1 root root 162 11 23 03:34 sin_value.c
-rw-r--r-- 1 root root 80 11 23 03:32 sin_value.h
main.c: The main purpose is to allow users to input angle data and call other three subroutines.
hello.c: output welcome message
sin_value.c: Calculate the sin value of the angle (360) entered by the user
cos_value.c: Calculate the cos value of the angle (360) entered by the user
Feel free to checkout what is inside those files using vim or cat.
Now, let's complie our codes:
gcc -c main.c hello.c sin_value.c cos_value.c
the command will compile all the codes and generate 4 *.o files.
Then, run gcc -o angle_cal main.o hello.o sin_value.o cos_value.o -lm to link all or files, and also the libmath library that we used for math calculation, and build our executable angle_cal
call ./angle_cal to run our executable and play with it.
TBA. about using make