Programming in Linux Environment

Programming in Linux Environment
Seoul National University
Interactive and Networked Robotics Lab.
Dongho Kang

Contents
• Introduction
• Programming using Vim editor
• Compiling and Makefile
• Version control with Git

Motivation
• Demo
• Hello World!
• swap()
• Benefits
• Linux is free!
• Support for most programming languages!
• Much better compatibility!

Demo: Hello World!
• Hello World in C, C++, Java, OCaml, Python
• Various programming language and environment.

Demo: swap()
• Assembly code for swap() function.
• GCC compiler
• Low level programming

Linux
• Unix-like Computer Operating System
• Initially released in 1991 by Linus Torvalds
• Free and open-source software
• GPLv2 and other free & open-source licenses
• Platforms
• IA32 (x86-32) / x86-64 / ARM / PowerPC / SPARC / PA-RISC …

Basic commands: Bash
• apt-get: package management
• cd: change directory
• clear: clear screen
• chmod: change the permission
• cp: copy files/folders
• mv: move files/folders
• dir: list the folders
• grep: search files
• mkdir: make directory
• wget: retrieve web pages of file
• rm: remove files
• rmdir: remove folders
• shutdown: shutdown / restart
• sudo: super user do

Basic commands: Bash
• For more commands:
http://ss64.com/bash/
http://tldp.org/LDP/abs/html/basic.html

Programming using Vim editor
• Vim installation
• HelloWorld.c
• Configuration with vimrc file
• Plugins and Vundle

Vim Installation
$ sudo apt-get update # package index update (if needed)
$ sudo apt-get upgrade # package upgrade (if needed)
$ sudo apt-get install vim # vim install

Vim
$ vim # open vim
$ vim a.c # create a.c and open
$ vim -O a.c b.c # vertical (2 files)
$ vimdiff a.c b.c # compare

HelloWorld.c
#include <stdio.h>
int main()
{
// why no indentation? (vimrc!)
printf("Hello World!n");
return 0;
}

GCC Compiling and Run
# build-essential is gcc, g++ etc..
$ sudo apt-get install build-essential
$ sudo apt-get install gcc
$ gcc HelloWorld.c
$ ./a.out
Hello World!

Vim shortcuts
• Be familiar with shortcuts: https://www.fprintf.net/vimCheatSheet.html
• Basic shortcuts and commands:
:q (quit vim)
:q! (quit without saving)
:w (save file)
:w <file name> (save file with name)
:wq (save and quit)
:wq <file name> (save file with name and quit)
:e <file> (edit file)
:a (append text after the cursor)
:A (append text at the end of the line)
:i (insert text before the cursor)
:I (insert text before the first non-blank)
:o (begin a new line below the cursor)
:O (begin a new line above the cursor)
d (delete text)
dd (delete line)
u (undo)
CTRL-R (redo)

Configuration with vimrc file
• Runtime configuration settings to initialize Vim
• File Path: ~/.vimrc

vimrc example
set nocompatible
set autoindent
set smartindent
set cindent
set number
set shiftwidth=4
set tabstop=4
set laststatus=2
set hlsearch
set showcmd
syntax on
For more example: help vimrc_example.vim in vim command mode or http://vimdoc.sourceforge.net/htmldoc/usr_05.html#vimrc_example.vim
and https://amix.dk/vim/vimrc.html

Plugins and Vundle
• Plugins: better way to customize Vim editor
• e.g. The NERD tree / fugitive / vim-airline …
• http://vimawesome.com/
• Management tools for Vim plugins
• Vundle / NeoBundle / VimPlug / Pathogen

Vundle Installation
• More details: https://github.com/VundleVim/Vundle.vim
• Git clone from Vundle repository (GitHub)
• Configure plugins via vimrc
• Install plugins with Vundle

Vundle example
set nocompatible " be iMproved, required
filetype off " required
" set the runtime path to include Vundle and initialize
set rtp+=~/.vim/bundle/Vundle.vim
call vundle#begin()
" alternatively, pass a path where Vundle should install plugins
"call vundle#begin('~/some/path/here')
" let Vundle manage Vundle, required
Plugin 'VundleVim/Vundle.vim'
" The following are examples of different formats supported.
" Keep Plugin commands between vundle#begin/end.
" plugin on GitHub repo
Plugin 'The-NERD-Tree'
Plugin 'bling/vim-airline'
Plugin 'zhaocai/GoldenView.Vim'
Plugin 'airblade/vim-gitgutter'
" All of your Plugins must be added before the following line
call vundle#end() " required
filetype plugin indent on " required
" To ignore plugin indent changes, instead use:
"filetype plugin on
"
" Brief help
" :PluginList - lists configured plugins
" :PluginInstall - installs plugins; append `!` to update or just
" :PluginSearch foo - searches for foo; append `!` to refresh local cache
" :PluginClean - confirms removal of unused plugins; append `!` to auto-
"
" see :h vundle for more details or wiki for FAQ
" Put your non-Plugin stuff after this line

Compiling and Makefile
• What is “compiling?”
• Compiling with gcc / g++ / javac …
• Make
• Writing makefile

Compiling example
• Simple example
• Function a(), b(), c() declared,
defined in different files.
• Use a(), b(), c() in main().
a.h
void a();
b.h
void b();
c.h
void c();
a.c
void a()
{
…
}
b.c
void b()
{
…
}
c.c
void c()
{
…
}
main.c
int main()
{
…
a();
b();
c();
…
}
Function declaration in .h
Function definition in .c
Function usage in main.c

Process of compiling
• Preprocessing
• Compiling
• Assembling
• Linking
Run (exec)
a.h b.h c.h
a.c b.c c.c main.c
a.o b.o c.o main.o
a.s b.s c.s main.s
Preprocessing
Compiling
Assembling
Linking

Compiling example
# compiling / assembling / linking
$ gcc -S *.c # compile .c to generate .s
$ gcc -c *.s # assemble .s to generate .o
$ gcc *.s # link .o to generate exec file
# generate exec at once
$ gcc *.c # compile, assemble and link .c
# generate exec with a name
$ gcc -o run *.c

Make
• A utility that automatically builds executable programs and
libraries from source code by reading files called Makefiles.
- Wikipedia
• Useful to manage big software projects includes many files.
• Compiling rules are written in “makefile” with Rule Syntax.
• Ref. CMake: generate makefile for cross-platform

Makefile
• Rules for compiling
• Target & Component (dependency)
• targets : prerequisites ; command
• e.g. hello: (no prerequisite) ; @echo “hello”
• Make searches the current directory for the makefile to use.

Writing makefile
target-name ... : list-of-dependencies ...
[TAB] command (gcc command: tab is necessary)
...
...
target-name: name of result file (object file or executable file)
list-of-dependency: dependency for target
command: gcc command for compiling

Make example
• Simple example
• Function a(), b(), c() declared,
defined in different files.
• Use a(), b(), c() in main().
a.h
void a();
b.h
void b();
c.h
void c();
a.c
void a()
{
…
}
b.c
void b()
{
…
}
c.c
void c()
{
…
}
main.c
int main()
{
…
a();
b();
c();
…
}
Function declaration in .h
Function definition in .c
Function usage in main.c

Make example
• Dependency graph
Run (exec)
a.h b.h c.h
a.c b.c c.c main.c
a.o b.o c.o main.o

Makefile example
run: main.o a.o b.o c.o
gcc -o run main.o a.o b.o c.o
main.o: main.c a.h b.h c.h
gcc -c main.c
a.o: a.c a.h
gcc -c a.c
b.o: b.c b.h
gcc -c b.c
c.o: c.c c.h
gcc -c c.c $ make: compile with makefile rules

Makefile macro & label
• Using macro to avoid command repeating
• $ make –p: check what kind of macro you can use.
• Internal macro: $* / $*.c / $*.o / $@ / $< …
• Label: name of macro
• OBJECTS: .o files
• CC: compiler
• CFLAGS: compile flag

Makefile macro & label
• Suffix rule
• Implicit rules for Make
• “how each target is ``made'' from the prerequisites or relied
on make magic to do the right thing.”
For more details: https://wiki.kldp.org/KoreanDoc/html/GNU-Make/GNU-Make.html
Programming with GNU Software (O’REILLY) Chap.7
# Form
s1s2:
commands to get s2 from s1
# Example
.c.o :
$(CC) $(CFLAGS) –c $<

Makefile example refined!
# labels
TARGET = test
OBJS = main.o a.o b.o c.o
CC = gcc
# suffix rules
.SUFFIXES: .c .o
# compile rules
c.o:
$(CC) -c -o $@ $*.c
$(TARGET): $(OBJS)
$(CC) -o $@ $(OBJS)
# dependencies
main.o: main.c a.h b.h c.h
a.o: a.c a.h
b.o: b.c b.h
c.o: c.c c.h
clean:
rm -f $(OBJS) $(TARGET)

Version Control with Git
• What is “Git”?
• Git basics
• Git on the server
• GitHub

Why we use Git?
When you need to edit your source code…

What is “Git”
• Widely-used version control system for software development.
• Full version tracking / Full-fledged repository with complete history
• Developed by Linus Torvalds (Initially released in 2005)
• Free software
• GNU General Public License v2 / GNU Lesser General Public License 2.1
• https://git-scm.com/

Git basics
• git init / git clone: create (or clone) a new repository
• git add: propose changes
• git commit: commit!

Git basics
• Branch
• git checkout –b <new branch>
• git checkout master
• git branch –d <branch to delete>
• git merge <branch to merge>

Git on the server
• git clone user@host:/remote/repo/path
• git commit
• git push origin <branch>

GitHub
• Web-based Git repository hosting service.
• Founded in 2008.
• Cost
• Free for public repos
• Paid for private repos
• GitHub Student Pack: https://education.github.com/pack
• Free for micro account ($7/month) with five private repos. (only for students)
• Other free developer packs including DigitalOcean, AWS etc. (only for students)

https://github.com/gokoreas/InRoL-Quadrotor-Platform-for-Research/blob/master/USB2PPM_FW/usb2ppm_fw/usb2ppm_fw.ino

Git tutorial
• Create new repository on GitHub.
• Hello Git! (coding)
• Git commit and push to remote.
• Modify code.
• Git commit and push to remote.

Git Clients
• Not for Linux
• GitHub Desktop
• Source Tree
• Linux
• GitKraket (Beta)
• gitg

Whole tutorial
• https://github.com/EastskyKang/Programming-in-Linux-
Environment-Tutorial
• Korean / English

Maybe next time…
• More details…
• Other useful tools for SW development in Linux environment.
• GDB – for debugging
• Open-source libraries / SDKs
• OpenCV / AscTec Research Platform / ROS …

Programming in Linux Environment

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