1. Absolute basics

Table 1. Absolute basics
Command Meaning

ls

Displays a list of files in the current working directory.

cd directory

change directories

passwd

change the password for the current user

file filename

display file type of file with name filename

cat textfile

throws content of textfile on the screen

pwd

display present working directory

exit or logout

leave this session

man command

read man pages on command

1.1. Key combinations

Table 2. Key combinations
Key or key combination Function

Ctrl+C

End a running program and return the prompt

Ctrl+Z

Suspend a program

ArrowUp and ArrowDown

Browse history. Go to the line that you want to repeat, edit details if necessary, and press Enter to save time.

Tab

Command or filename completion; when multiple choices are possible, the system will either signal with an audio or visual bell, or, if too many choices are possible, ask you if you want to see them all.

Tab Tab

Shows file or command completion possibilities.

Shift+PageUp and Shift+PageDown

Browse terminal buffer (to see text that has "scrolled off" the screen).

1.2. ls -l

# ls -al
drwxrwxr-x 4 zeus zeus  4096 Οκτ  23 21:55 .
drwxrwxr-x 9 zeus zeus  4096 Οκτ  15 14:28 ..
drwxrwxr-x 8 zeus zeus  4096 Οκτ  23 21:55 .git
drwxrwxr-x 4 zeus zeus  4096 Οκτ  14 20:24 install
crw-------   1 root root        5,   1 Οκτ  23 21:22 console
lrwxrwxrwx   1 root root            11 Οκτ  23 21:21 core -> /proc/kcore
drwxr-xr-x   4 root root           100 Οκτ  23 21:22 cpu
crw-------   1 root root       10,  59 Οκτ  23 21:21 cpu_dma_latency
crw-------   1 root root       10, 203 Οκτ  23 21:21 cuse
-rw-rw-r-- 1 zeus zeus  1517 Οκτ  23 21:55 INSTALL.md
-rw-rw-r-- 1 zeus zeus 33883 Οκτ  15 14:28 LICENSE
-rw-rw-r-- 1 zeus zeus   691 Οκτ  17 11:13 README.md

1.2.1. File types

This table gives an overview of the characters determining the file type:

drwxrwxr-x 4 zeus zeus 4096 Οκτ 14 20:24 install
Table 3. File types in a long list
Symbol Meaning

-

Regular file

d

Directory

l

Link

c

Special file

s

Socket

p

Named pipe

b

Block device
-rw-rw-r-- 1 zeus zeus 1517 Οκτ 23 21:55 INSTALL.md

1.2.2. Access rights

Table 4. Access rights
Code Meaning

0 or -

The access right that is supposed to be on this place is not granted.

4 or

read access is granted to the user category defined in this place

2 or

write permission is granted to the user category defined in this place

1 or

execute permission is granted to the user category defined in this place

1.2.3. User group codes

Table 5. User group codes
Code Meaning

u

user permissions

-rw-rw-r--

g

group permissions

-rw-rw-r--

o

permissions for others

-rw-rw-rw-

1.2.4. Exercises

touch example
chmod 400 example
ls -l example
chmod 500 example
ls -l example
chmod 600 example
ls -l example
chmod 644 example
ls -l example
chmod 660 example
ls -l example
chmod 700 example
ls -l example
chmod 755 example
ls -l example
chmod 775 example
ls -l example
ls -l example
chmod 777 example
ls -l example