Linux And The Console

SPACE for next slide

Shift+SPACE for previous slide

Why are we having this session?

What is *nix?

*nix represents Unix and Unix like systems

Why Linux?

Why not Linux?

The "Hello World!" program

$ echo 'Hello World!'
Hello World!
$ █

Everything is a FILE on *nix systems

Environment variables

These variables govern the way applications communicate with the OS to access certain resources.

Some examples are:

Most basic commands

pwd - Shows value of $PWD

ls - List files in $PWD

cd path - Change $PWD

What is a Path?

A path defines the location of a file in the file system

Types of Path

Special paths

Getting help

man ls          # Manual entry for ls
help pwd        # Shell's pwd help
/bin/pwd --help # Command specific help

Time elapsed since last startup

uptime -p

up 2 days, 23 hours, 38 minutes

"/" - The Root directory

which cmd - Prints path of an executable

/sbin, /bin - Location of commonly used binaries

/home/username - Home folder of username

/boot - Boot files are located here

Each and every command returns an integer after execution

Make a directory

mkdir <dir_name>

Make an empty file

touch <file_name>

Show contents of a file

cat <file_name>

Remove an empty directory

rmdir <dir_name>

Use this when safety is the first priority

Remove any directory

rm -rf <dir_name>

Editors

nano (Cheatsheet)

M = ESC or Alt
^ = Ctrl

vim (Cheatsheet)

It is a modal editor.

Remember

:q! - Force Quit

dd - Deletes a line

v - To enter visual mode

Use h, j, k and l keys to select the region.

:x - Save and Quit

:set autoindent - Auto indent

Learn advanced vim from

Controlling processes

Ctrl+C sends force quit signal to a running process

Ctrl+Z to pause a process

After pausing you have two options

Run a process in the background

<full_command> &

List running processes

ps -e   # Gives simple list
ps aux  # Gives verbose list
top     # Priority based ordering of processes

Kill a process

kill 1234           # Like ^C
killall -9 firefox  # Force kill

File redirection

ls -l > ls.txt     # stdout to ls.txt
ls /x 2> lserr.txt # stderr to lserr.txt
cat < ls.txt       # stdin from ls.txt

grep - Finding a string in file(s)

grep import file1 file2  # Find "import" in file1 and file2
grep -r import dir  # Recursively search in a dir
grep -n import file1  # Show line numbers of matches
grep -i import file1  # Ignore case
grep -rI import *.txt dir *.py  # Ignores binary files

find - Finding a file in a dir

find dir -name '*.py'  # Remember the single quote
find dir -iname '*sys*'  # Case insensitive search
find dir -type f -name '*.ini'  # Only show files
find dir -type f -empty  # Show empty files only

head - Show first few lines

tail - Show last few lines

Pipes

Passing output from one program to another

ps -e | grep py

Nested commands

Use one program’s output as a parameter of another command

ls -l `which python`

Thank you