three

Question 1

Time out a read format

Answer 1

read -t 10 -p “info” variabel

if the variable is not input within the standard time, the process will abort

Question 2

what is the internal field separator

Answer 2

$IFS

Question 3

in order to display the value of IFS, what can we do?

Answer 3

cat -etv

Question 4

read from string

Answer 4

read var1 var2 var3

Question 5

How to change the internal Field Separator

Answer 5

IFS=delimiter
restore it to its old value
IFS=”$old”

Question 6

read -r

Answer 6

if -r is specified, the backslash is part of the line, not as an escape character

Question 7

perform integer expression

Answer 7

$((expression including integers only))

Question 8

the integer operator in $(())

Answer 8

++ pot-increment

**exponential

Question 9

create an integer variable

Answer 9

declare -i y=value

Question 10

create readonly variable

Answer 10

readonly var
the var can be declared earlier than the readonly expression, once var is defined as readonly, it cannot be changed or unset

Question 11

variable existence check

Answer 11

${var:?info}

Question 12

local variables

Answer 12

user defined not exported

Question 13

environmental variables

Answer 13

exported

will be passed to subprocesses or subshells

Question 14

create readonly variable

Answer 14

readonly var
the var can be declared earlier than the readonly expression, once var is defined as readonly, it cannot be changed or unset