Pattern matching and searching

Question 1

Which command enables users to search for strings or patterns within the content of a file?

Answer 1

grep

grep [-options] pattern filename

Question 2

What does “grep -i” mean?

grep –i hall /student_files/day1/grepFile

Answer 2

grep –i: ignore case

Both upper or lower case is fine.

Question 3

What does “grep -n” mean?

grep –n hall /student_files/day1/grepFile

Answer 3

grep –n: gives you the line number

Question 4

What does “grep -v” mean?

grep –v hall /student_files/day1/grepFile

Answer 4

grep –v: returns everything but what the matcher

Question 5

What does “grep -w” mean?

grep –w hall /student_files/day1/grepFile

Answer 5

grep –w: match the whole word

Question 6

What does “grep -c” mean?

grep –c hall /student_files/day1/grepFile

Answer 6

grep –c: count the number of lines matching

Question 7

What are Literal and meta character(s)?

Answer 7

Literal: “coffee”
Metacharacter: [ ] ! * . ? $ \ { } ( )
Escape sequence: \

Question 8

Metacharacters

Answer 8

^: Match at start of line

$: Match at the end of line

. : Match a single character

*: Match zero or more occurrences of the preceding character

.*: Match with any number of characters

: Escape the metacharacter and treat them as a literal

Question 9

What does the following command mean?

grep ‘^[0-9]’ /student_files/day1/grepFile

Answer 9

grep ‘^[0-9]’ /student_files/day1/grepFile

^: Match at start of line
[ ]: Match anything in the [ ] for 1 character position

So it means: Within the grepFile, find any line that starts with 0-9.

Question 10

What does the following command mean?

grep ‘6.’ /student_files/day1/grepFile

Answer 10

grep ‘6.’ /student_files/day1/grepFile

. : Match a single character

Question 11

What does the following command mean?

grep ‘6.’ /student_files/day1/grepFile

Answer 11

grep ‘6.’ /student_files/day1/grepFile

: Escape the metacharacter and treat them as a literal

Question 12

What does the following command mean?

grep ‘192.*0’ /student_files/day1/grepFile

Answer 12

grep ‘192.*0’ /student_files/day1/grepFile

.*: Match with any number of characters

Question 13

What does the following command mean?

grep ‘192*0’ /student_files/day1/grepFile

Answer 13

grep ‘192*0’ /student_files/day1/grepFile

*: Match zero or more occurrences of the preceding character

Question 14

What does the “find” command do?

Answer 14

find [where to search] [what to search for] [action]

The find command enable users to locate files in the File System.

find searches through the directory tree recursively, locates the files and applies an optional action to the files found