shell text wrangling

Question 1

<

Answer 1

redirecting input

Question 2

>

Answer 2

redirecting output

Question 3

1>

Answer 3

redirecting output

Question 4

2>

Answer 4

redirecting error

Question 5

/dev/null

Answer 5

a special device file that discards all data written to it

Question 6

head

Answer 6

used to print the first n lines (default 10)

Question 7

tail

Answer 7

used to print the last n lines

Question 8

.

Answer 8

any single character

Question 9

[abc]

Answer 9

any of the characters in the brackets

Question 10

[a-z]

Answer 10

any character in the range a-z

Question 11

[^a-c]

Answer 11

means not containing a, b or c

Question 12

(a|b)

Answer 12

either a or b

Question 13

*

Answer 13

0 or more

Question 14

+

Answer 14

1 or more

Question 15

?

Answer 15

exactly 0 or 1

Question 16

{X}

Answer 16

exactly X characters of the specific kind

Question 17

{X,Y}

Answer 17

means we want X to Y characters of the specific kind

Answer 18

start of the line

Question 19

$

Answer 19

end of the line

Question 20

sed -g

Answer 20

replaces all matches, not only the first one

Question 21

awk -F””

Answer 21

field delimiter

Question 22

~ matches

Answer 22

!~ does not match

Question 23

$0

Answer 23

whole line

Question 24

$N

Answer 24

N field

Question 25

FS

Answer 25

input field separator

Question 26

OFS

Answer 26

output field separator

Question 27

NF

Answer 27

number of fields

Question 28

NR

Answer 28

number of records(lines)

Question 29

RS

Answer 29

record separator

Question 30

ORS

Answer 30

output record separator

Question 31

FILENAME

Answer 31

current file name