CSSE2310 - Final Exam - Bash commands

Question 1

How do you handle a question like this ….

“Get the first line of file.c which contains the word “car”. “

Answer 1

1. start with getting the first line

“head -1 file.c”

2. Pipe this into grep to search for “car”

“head -1 file.c | grep “car”

Answer: “head -1 file.c | grep “car”

OR

cat file.c | head -1 | grep “car”

Question 2

How do you handle a question like this …

“Get the last 4 lines in file.c and print them alphabetically”

Answer 2

1. start with getting the last four lines

“tail -4 file.c”

2. Pipe this into sort to make them alphabetical

“tail -4 file.c | sort

Question 3

How do you handle a question like this …

“Get the lines in file.c that contain both cat and dog”

Answer 3

1. start with searching the file for cat

grep -n “cat” file.c

2. Pipe this into a grep to get the lines that also contain dog

grep -n “cat” file.c | grep “dog”

OR

cat file.c | grep “cat” | grep “dog”

Question 4

How do you handle a question like this …

Get the lines in file.c that contain cat not case sensitive

Answer 4

1. start with searching the file for lines that contain cat

grep -n “cat” file.c

2. Use dash i to include not be case-sensitive

grep -i -n “cat” file.c

Question 5

How do you handle a question like this …

Get all the lines in the current directory that contain the word cat

Answer 5

1. start with searching the current directory that contain cat

grep -r cat .

Question 6

How do you handle a question like this …

Count the number of lines in the file “file.c” that contain the word “dog”

Answer 6

1. Use -c with grep

grep -c “dog” file.c

OR

grep “dog” file.c | wc -l

OR

cat file.c | grep “dog” | wc -l

Question 7

How do you handle a question like this …

Get the files that contain “dog” in the current directory?

Answer 7

1. Use -l with grep

grep -r -l “dog” .

OR

grep -l -r “dog” .

Question 8

How do you handle a question like this …

Get the 2nd and 4th column of the file.c, delimited by tabs.

Answer 8

1. Use cut to get the columns

cut -f 2,4 file.c

Question 9

How do you handle a question like this …

Get the 2nd to 5th column of the file.c, delimited by tabs.

Answer 9

1. Use cut to get the columns

cut -f 2-5 file.c

Question 10

How do you handle a question like this …

Get the 5, 7 th column of the file.c delimited by “,”

Answer 10

1. Use cut to get the columns and -d for the delimiter

cut -f 5,7 -d “,” file.c

Question 11

How do you handle a question like this …

Get all the lines of the file.c where “cat dog” appears EXACTLY.

Answer 11

1. Use grep -c to count the number of occurrences

grep -w “cat dog” file.c

Question 12

How do you handle a question like this …

Get the first 4 lines of the file file.c

Answer 12

1. Use head command and -n

head -4 file.c

Question 13

How do you handle a question like this …

Get the lines in file.c that contain cat OR dog

Answer 13

1. use grep command and \ |

grep “cat|dog” file.c

OR

grep -n “cat|dog” file.c

Question 14

How do you handle a question like this …

Get the lines in file.c that contain cat AND dog

Answer 14

1. use grep command and .*

grep “cat.*dog” file.c

Question 15

How do you handle a question like this …

Get the fifth line of the file file.c

Answer 15

1. Step 1. use the cat command to show the contents on screen.

cat file.c

2. pipe into the head command to say what line you want to read

cat file.c | head -5

3. pipe into the tail to say how many lines you want to read from the head command

cat file.c | head -5 | tail -1

OR

head -5 file.c | tail -1

Question 16

How do you handle a question like this …

Get the number of times dog appears in the first column of file.c

Answer 16

Cut the columns first and then count. So…

cut -f 1 file.c

Then pipe into grep and count the number times dog appears

cut -f 1 file.c | grep -c dog

OR

cat file.c | cut -f 1 | grep “dog” | wc -l

Question 17

How do you handle a question like this …

Show all instances of zazu which you are running on the system (Your computer)

Answer 17

First off, get the processes on the system which are

ps -u $USER

2. Pipe this into grep and look for zazu

ps -u $USER | grep zazu

Question 18

How do you handle a question like this …

Get all the files which have are four characters or longer

Answer 18

1. Use ls -d to list with a delimiter

ls -d

2. Use wildcards to select 4 or more

ls -d ????*

Question 19

How do you handle a question like this …

Add /yo/yo/ma to the list of directories

Answer 19

Gotta reassign the path, using PATH=$PATH

PATH=$PATH

Append to the path

PATH=$PATH:yo/yo/ma

Question 20

How do you handle a question like this …

Get the first two lines of the file bob.c

Answer 20

Use the head command

head -2 bob.c

Question 21

How do you handle a question like this …

Show the commands which will be run from this directory

Answer 21

Use the echo command

echo $PATH

Question 22

How do you handle a question like this …

Show the first column of the file bob.c (columns are separated by commas).

Answer 22

1. Use the cut command and -f to specify the column to read

cut -f 1

2. Add the -d as a delimiter

cut -f 1 -d “,” bob.c

OR

cat bob.c | cut -f 1 -d “,”

Question 23

How do you handle a question like this …

Show all instances of vim running on the system (not just you)

Answer 23

1. Use the ps -A to get all the processes

ps -A

2. Pipe into grep

ps -A | grep vim

Question 24

How do you handle a question like this …

Count how many files contain at least five characters

Answer 24

1. Get all the files that have at least 5 characters

ls -d ?????*

2. Pipe in and count how many files there are (use wc -l)

ls -d ?????* | wc -l

Question 25

How do you handle a question like this ... Delete all the files that start with s and d but not sd?

Answer 25

1. use the rm function and wild card, must have at least one character in between so use ? rm s?*d

Question 26

How do you handle a question like this ... Output the name of the first directory which will be used to search for executables? (Hint: ":" is a separator)

Answer 26

1. Use echo $PATH to get the execuables echo $PATH 2. Pipe into cut -f 1 and delimit the semicolon echo $PATH | cut -f 1 -d ":"

Question 27

How do you handle a question like this ... Kill the process 1234

Answer 27

1. Need to use the kill command -9 , to say that this is not ignorable kill -9 1234

Question 28

How do you handle a question like this ... Show all the files and permissions for all the files in the current directory.

Answer 28

1. Need to list so use ls, "all the files" so need to use -a, for the permissions gotta use -l ls -al

Question 29

How do you handle a question like this ... Show the first line of the file bob.c that contains the word hello

Answer 29

1. Use grep to search for hello grep "hello" bob.c 2. Pipe in and get just the first line using head grep "hello" bob.c | head -1 OR cat "bob.c" | head -1 | grep "hello"

Question 30

How do you handle a question like this ... Count the number of .c files in the current directory

Answer 30

1. list all the .c files in the current directory ls *.c 2. pipe in and use wc -l to get the number of occurences ls *.c | wc -l

Question 31

How do you handle a question like this ... Copy all the .c files in the current working directory to the /dest folder. Change all their names to start with old_

Answer 31

1. Use cp to copy all the .c files to the cp *.c dest/ 2. Need to loop through each one and change its name for file in dest/*.c; mv dest/$file old_$file.c; done;

Question 32

How do you handle a question like this ... Change all the .pdf files in the current working directory to be prefixed with "new_".

Answer 32

Use a for loop for file in *.pdf; do mv $file new_$file; done

Question 33

How do you handle a question like this ... Remove the prefix "old_" from all of the .pdf files in the current working directory.

Answer 33

Use a for loop for file in *.pdf; do mv $file ${file#old_}; done

Question 34

How do you handle a question like this ... Remove the suffix ".c" from all of the files in the current working directory.

Answer 34

Use a for loop for file in *.c; do mv $file ${file%.c}; done

Question 35

What is the difference between the grep flags - r - n - c

Answer 35

- c : Counts the number of lines that this word appears - r: Recursively searches the directories below the current directory. - n: Gives the line number and the contents of the output