UNIX

Question 1

Read / Write privileges

Answer 1

Three triplets on the left. Then come owner and group. Read, write, execute.
example: drwxrwsr-x

rw-r–r–
110100100

Question 2

Change permissions

Answer 2

chmod [code] file

chmod +w abc

Question 3

Change the owner of a file

Answer 3

chown

Question 4

Change group for a file

Answer 4

chgrp

Question 5

Get the security details of a file (e.g. who owns it, who is group)

Answer 5

getent

e.g. getent group cs201ta

Question 6

Read a file and execute the commands you find in that file

Answer 6

source OR .

e.g. source myinstructions OR ./myinstructions

OR

NEWPROG=ls -l
echo $X

Question 7

Tell us where a program is (e.g. where is the program ls?)

Answer 7

which ls

Question 8

Tell me what groups I’m a part of

Answer 8

id

Question 9

Tell me what processes I’m running

Answer 9

ps

Question 10

Tell me all the environment variables

Answer 10

set

Question 11

Search path for commands

Answer 11

echo $PATH

Question 12

Give programs an alias

Answer 12

alias
e.g. alias now=date
alias myls ls

Question 13

Put commands in a file, then alias, then execute

Answer 13

echo date > dateprog
alias mydate=./dateprog
mydate
» [Tells me the date]

Question 14

Tell me the present working directory or the past one

Answer 14

echo $PWD

echo $OLDPWD

Question 15

Random number

Answer 15

echo $RANDOM

Question 16

Tell me home directory

Answer 16

echo $HOME

Question 17

Create an environment variable

Answer 17

assignment operator =

TODAY=”Thursday”
echo $TODAY
» Thursday

Question 18

Tell me my user ID or UID

Question 19

How to evaluate an expression

Answer 19

expr (e.g. expr 20 + 4)

double parens e.g. echo $((20 + 4))

square brackets e.g. echo $[20 + 4]

Question 20

Go back n commands

Answer 20

!-n

E.g. !-5

Question 21

Tell me what is happening in the foreground

Answer 21

fg

Question 22

Tell me the type of a program

Answer 22

type

e.g. type ls
“Ls is aliased to…”