shell scripting

Question 1

$x

Answer 1

accessing a variable

Question 2

‘$x’ vs. “$x”

Answer 2

string literal vs. variable

Question 3

special characters:

Answer 3

” , $, `, “, *

Question 4

read

Answer 4

reads input; by default, splits the input into words, considering <space>, <tab>, and <newline> characters as word delimiters</newline></tab></space>

Question 5

read -s

Answer 5

suppress the printout of the input

Question 6

read -p

Answer 6

specify prompt message

Question 7

read -t N

Answer 7

timeout after N seconds

Question 8

read -n N

Answer 8

read exactly N characters

Question 9

:-

Answer 9

replace a empty variable with a default value

Question 10

:=

Answer 10

assign default values to empty variables

Question 11

-n <string></string>

Answer 11

length non-zero

Question 12

-z <string></string>

Answer 12

length zero

Question 13

<string>
</string>

Answer 13

string non-zero

Question 14

-eq

Answer 14

is equal

Question 15

-neq

Answer 15

not equal

Question 16

-gt

Answer 16

greater than

Question 17

-ge

Answer 17

greater than or even

Question 18

-lt

Answer 18

lesser than

Question 19

-le

Answer 19

lesser than or even

Question 20

-e

Answer 20

exists

Question 21

-f

Answer 21

exists and is a regular file

Question 22

-d

Answer 22

exists and is in directory

Question 23

-s

Answer 23

exists and its size is larger than zero

Question 24

-nt

Answer 24

newer than

Question 25

-ot

Answer 25

older than

Question 26

continue

Answer 26

skips the rest in the current iteration and starts a new iteration

Question 27

$0

Answer 27

name of the script

Question 28

$1-$9

Answer 28

argument

Question 29

$@

Answer 29

all arguments

Question 30

$#

Answer 30

number of arguments

Question 31

$?

Answer 31

return code of the previous command

Question 32

$$

Answer 32

PID of the current command

Question 33

!!

Answer 33

entire last command with arguments

Question 34

$_

Answer 34

last argument of last command