Bash Shell

Question 1

make a local variable

Answer 1

VAR1=variableAttributeHere

Question 2

how do you make variable environmental variable?

Answer 2

export VAR1
VAR1 is the variable

Question 3

delete environmental variable

Answer 3

unset VAR1

Question 4

prevent inadvertent overwriting

Answer 4

set -o noclobber

to disable run:
set +o noclobber

when using this > operator

Question 5

redirect standard error

Answer 5

find / -name core -print 2> /dev/null

Question 6

redirect both standard and output error

Answer 6

ls /usr /cdr &> outerr.out

This example will produce a listing of the /usr directory and save the result in outerr.out. At the same time, it will generate an error message complaining about the non-existence of /cdr, and it will send it to the same file as well.

Question 7

see all previously run commands

Answer 7

history

Question 8

move cursor to beginning of command line

Answer 8

Ctrl a
home

Question 9

erase the entire line

Answer 9

ctrl u

Question 10

erase from the cursor to the end of the command line

Answer 10

ctrl k

Question 11

move curse to the right by one word

Answer 11

alt f

Question 12

move cursor to the left one word

Answer 12

alt b

Question 13

display previous working directory

Answer 13

echo ~-

Question 14

make an alias

Answer 14

alais rm=’rm -i’

Question 15

list all hidden directories

Answer 15

ls -d .*

Question 16

match exactly one character

Answer 16

?
ls /var/log/????
This will fine everything in var/log with exactly 4 characters

Question 17

match either a set of characters or a range of characters for a single character position

Answer 17

[] - square brackets
ls /usr/bin/[yw]* = will find all file starting with y and w
ls -d /etc/systemd/system/[m-o]* = all file with m through o
ls -d /etc/systemd/system/[!m-o]* = ! excludes m through o

Question 18

search for user in passwd file

Answer 18

grep user1 /etc/passwd

Question 19

search for things at the beginning of the line

Answer 19

grep ^root /etc/passwd

Question 20

search for things at the end of a line

Answer 20

$
grep bash$ /etc/passwd

Question 21

show entire login.defs file but EXCLUDE all empty lines

Answer 21

grep -v ^$ /etc/login.defs
-v - inverts so it excludes all the empty lines - ^$

Question 22

case insensitive search

Answer 22

-i
grep -i path /etc/bashrc
will find path, PATH,Path etc….

Question 23

which character can be used as an OR operator within grep

Answer 23

- pipe
ls -l /etc | grep -E ‘cron|ly’ = cron pipe ly
will find all file with cron or ly in the title

Question 24

run the top command in the background

Answer 24

top &

Question 25

list all jobs

Answer 25

jobs -l

Question 26

name the three system-wide startup files

Answer 26

/etc/bashrc
/etc/profile
/etc/profile.d

Question 27

name the per-user shell start up files

Answer 27

.bachrc
.bash_profile
.gnome2/

Question 28

hostcustomize your prompt

Answer 28

export PS1=”< $LOGNAME on $(hostname) in $PWD > “

prompt will not look like:
< user1 on server1 in /home/user1 >

Edit .bash_profile with the exact same command to make persistent

Question 29

which directory location stores most privileged commands

Answer 29

/usr/sbin