Lab 1 - Introduction: Environment setup. UNIX command line introduction. C programming in the UNIX command line.

Introduction: Grading/attandance rules, Lab tests on the exam server, Course website

Environment setup

Windows options:
- http://www.cs.ubbcluj.ro/~rares/course/os/res//env-setup/windows/ (Homework - Setup linux server on a Virtual machine)
- Ubuntu App (Windows 10 and above, enabeling WSL) and use ssh command to connect to any server >> ssh username@linux.scs.ubbcluj.ro (then input password)
- Download Putty for ssh connection to a server from CAMPUS at the lab >> Host Name: linux.scs.ubbcluj.ro Port: 22 (then use your scs username and password)
- to connect to the server remotely from your HOME (Video) >> Host Name: scs.ubbcluj.ro Port: 8937 (then use your scs username and password)
MacOS: https://brew.sh/
Linux: all set

UNIX command line introduction

It is the most powerful and flexible way to get things done in an operating system, provided that you know what you are doing.

a. Linux: Sh, Bash, Ksh, ...
b. Windows: Cmd (remember from assembly, building, linking and executing code), Powershell, ...
c. MacOS: Terminal (actually Bash)

A. Basic unix commands

ls list content of current directory
mkdir creates new directory
cd changes the current directory
echo displays text
ps display running processes

ls
mkdir numefir
cd numedir
cd ..
cd ../..
cd /home
echo $HOME
cd $HOME (or cd ~ )
clear
cp sursa destinatie (ex. ../fisier.txt .) ; cp cale_fisier cale_director
cp *.ext .
cp -R ../bbbc .
mv sursa destinatie
mv numedirvechi numedirnou
rm fis.txt
rmdir numedir
(rmdir -r recursiv...)
ls -d */
ls -l
man ls (use keyboard to browse, to exit type Q)
ls *.ext
date
cal
grep cuvand numefisier
ifconfig
ping google.ro
ps
kill -9 PID (we'll try this later :D )
touch fis.txt
echo "Hello Pumba!" > fis.txt
echo "Goodbye my lover!" > fis.txt
cat fis.txt | sort
finger

Grouping/separating comds with:
; | && || () {}

Redirecting:

0 - stdin

1 - stdout

2 - stderr

output: > ... (redirect output to... and overwrite) >> ... (append to ...)

input: ... < (provide input to ...) ... << DELIMITER (read input continuously until the specified DELIMITER comes up)

error: 2>... (redirect standsrd error to ..)

>&1 >&2

pipe: cmd1 | cmd2 (the output from cmd1 will be input for cmd2); eaxmple: cat fis.txt | sort

Homework 1: ls, cd, mkdir, pwd, man, head, tail, cut, clear, kill, echo, less, cp, find, zip, unzip, tar, gzip, gunzip, write, who, finger, ping, cat, sort, wc, rm, chmod, passwd, ps, fg, bg, file, w, mv, df, du, comm, diff, mesg, date, cal, nohup, ssh, scp, pine/mutt/alpine (for email), mesg n, whatis, apropos

B. Key combinations and terminal usage tips

Ctrl+S locks the console => Ctrl+Q to unlock
Ctrl+C terminates the current process
Ctrl+Z send the current process in background (Ctrl+L to restore or fg command)
Ctrl+D exit (runs the exit command)

Double click to copy
Right mouse click to paste
Use keyboard arrows up and down to browse through history and reuse commands

C. Manual

online: https://linux.die.net/man/
man command (ex. man ls )

C programming in the UNIX command line

A. Command line editors

vim
emacs
nano
joe
...

vim editor

2 working modes: INSERT / COMMAND
shortcuts: i, Esc, x, dd, dw, /, V, y, p
commands: :w, :q, :x, :q!
configure vim by creating ~/.vimrc file with content:

syntax on
set tabstop=4
set expandtab

Homework 2: learn vi (or a similar editor)

VIM interactive tutorial: http://www.openvim.com/tutorial.html

Practice recovering a file in VIM: https://www.zachpfeffer.com/single-post/Practice-Recovering-a-File-in-Vim

B. Coding in C

To open the code editor:

>> vi helloworld.c

>> joe helloworld.c

etc.

C. Compile, debug and execute

To compile (this will create the output executable file names hello or print on the screen the compiling errors):

>> gcc -Wall -o hello helloworld.c

To execute:

>> ./hello

Hello world example program:

helloworld.c

--------------------------------------------
#include <stdio.h>
int main(int argc, char** argv) {
printf(“Hello COVID world!\n”);
return 0;
}

--------------------------------------------

Homework 3: Learn/remember C (not C++). Ex. Write a C program that reads 10 real numbers, stores them into an array and computes the average, min and max.