linux commands

Question 1

How do you connect to bandit.labs.overthewire.org on port 2220 with the username bandit0?

Answer 1

ssh bandit0@bandit.labs.overthewire.org -p 2220

Question 2

Standard Unix/Linux command used to check the information of disk usage of files and directories on a machine?

Answer 2

du

Question 3

What are two ways to read a file named ‘-‘ ?

Answer 3

1. cat

Question 4

How do you read a file that has spaces in the filename?

Answer 4

place the filename in single quotes

EX: cat ‘spaces in the filename’

Question 5

How do you display hidden files in a directory?

Answer 5

ls -a

Question 6

How do you connect to bandit.labs.overthewire.org on port 2220 with the username bandit0, and using a password stored in a file named “bandit0”?

Answer 6

sshpass -p ‘cat bandit0’ ssh bandit0@bandit.labs.ovedrthewire.org -p 2220

Question 7

How would you determine the types of files in a directory named “inhere” that all start with “-“?

Answer 7

file ./*

Question 8

How would you read all the contents of every file within a directory named “inhere” that all start with “-“?

Answer 8

strings ./*

Question 9

How would you search all subdirectories of the current directory for a file that matches the following characteristics:

• human-readable
• 1033 bytes in size
• not executable

Answer 9

find ! -executable -size 1033c

Question 10

How would you search the entire server for a file that matches the following characteristics, and do not show any permission denied errors (should only return one file):

• owned by user bandit7
• owned by group bandit6
• 33 bytes in size

Answer 10

find / -size 33c -user bandit7 -group bandit6 2>/dev/null

Question 11

Search the file “data.txt” for the line with the word “millionth”.

Answer 11

cat data.txt | grep millionth

Question 12

How do you search the file “data.txt” for the line of text that appears only once.

Answer 12

cat data.txt | sort | uniq -c

Question 13

After using this above command (cat data.txt | sort | uniq -c) to sort the file “data.txt” for unique lines, you have a bunch of lines that occur 10 times (shows 10 at the start of the line) and one line that occurs once. How can you remove all of the lines that start with ‘10’ to only leave the line that starts with ‘1’?

Answer 13

cat data.txt | sort | uniq -c | grep -v “10”

Question 14

Search the file “data.txt” for the few human-readable strings that begin with several ‘=’ characters.

Answer 14

strings data.txt | grep “=”

Question 15

What is the sign that something is Base64 encoded?

Answer 15

The string ends in 0, 1, 2, or 3 “=” sign

Question 16

How do you decode the string of data within the file “data.txt” that is Base64 encoded?

Answer 16

cat data.txt | base64 -d

Question 17

How do you get a password from the file data.txt, with a string where all lowercase (a-z) and uppercase (A-Z) letters have been rotated by 13 positions?

Answer 17

cat data.txt
– displays the text “Gur cnffjbeq vf 5Gr8L4qetPEsPk8htqjhRK8XSP6x2RHh”–
echo “Gur cnffjbeq vf 5Gr8L4qetPEsPk8htqjhRK8XSP6x2RHh” | rot13

Question 18

How do you take a hexdump file and reverse the hexdump process to a readable file?

Answer 18

xxd -reverse data.txt > newfile

Question 19

How do you uncompress the file “data.gz”?

Answer 19

gunzip data.gz

Question 20

How do you uncompress the file “data.bz2”?

Answer 20

bunzip2 data.bz2

Question 21

How do you uncompress a file “data.txt” that is a POSIX tar archive file type?

Answer 21

tar xf data.txt

Question 22

How do you ssh to ‘localhost’ with user bandit14 using the key “sshkey.private” located in the current directory?

Answer 22

ssh -i sshkey.private bandit14@localhost

Question 23

How do you netcat a password that is in /etc/bandit_pass/bandit14 to port 30000 on localhost?

Answer 23

cat /etc/bandit_pass/bandit14 | nc localhost 30000

Question 24

How to list all contents, including permissions, and hidden files of the current directory?

Answer 24

ls -la

Question 25

How do you make a python file named file.py executable?

Answer 25

chmod +x file.py

Question 26

How would you make "foobar" provide the same results in the command line as "ls -la"? Where would you make the change in order for it to persist after reboot?

Answer 26

alias foobar='ls -la' make ~/.bashrc to make it persist after reboot

Question 27

How do you write text to a file?

Answer 27

echo Hello World > peanuts.txt

Question 28

How do you write text to a file, without deleting any existing text (append new text to the end of the existing file)?

Answer 28

echo Hello World >> peanuts.txt

Question 29

What is the file descriptor for stdin, stdout, and stderr?

Answer 29

- stdin = 0 - stdout = 1 - stderr = 2

Question 30

How would you redirect the standard error of "ls /fake/directory" to a special file that will discard any input?

Answer 30

ls /fake/directory 2> /dev/null

Question 31

What does the pipe operator "|" do?

Answer 31

allows us to get the stdout of a command and make that the stdin to another process.

Question 32

How would you write the output of "ls -la /etc" to a file and to the screen?

Answer 32

ls -la /etc | tee file.txt

Question 33

How do you display the first 10 lines of file.txt?

Answer 33

head file.txt

Question 34

How do you see the last ten lines of file.txt?

Answer 34

tail file.txt

Question 35

How do you get the unique values of a file?

Answer 35

uniq -u file.txt

Question 36

How would get the number of times a line appears in a file?

Answer 36

uniq -c file.txt

Question 37

How would you get lines that are duplicated in a file?

Answer 37

uniq -d file.txt

Question 38

What information about a file does "wc" provide?

Answer 38

- number of lines - number of words - number of bytes

Question 39

How would you fine all of the instances of the word "Hello" in file.txt?

Answer 39

grep Hello file.txt

Question 40

How would you list all of the files in the /etc directory with ".conf" extension?

Answer 40

ls /etc | grep .conf

Question 41

How would you print all of the lines of file.txt that begin with "Hello"?

Answer 41

grep ^Hello file.txt

Question 42

How would you print all of the lines that end with "seahorse"?

Answer 42

grep seahorse$ file.txt

Question 43

How would you print all of the lines that start with the letter "H" in file.txt?

Answer 43

grep H. file.txt

Question 44

How would you print all of the lines that start with either "dig", "dug", or "dog" in file.txt?

Answer 44

grep d[iou]g file.txt

Question 45

How would you print the lines that start with "dog" and "dug", but not "dig"?

Answer 45

grep d[^i]g file.txt

Question 46

Using the vim editor, how do you find all instances of the word "Hello", and how do you advance through each instance of "Hello" found in the file?

Answer 46

- /Hello - press 'n' to advance forward - press 'N' to go backwards

Question 47

Print the relative file paths, one path per line for all filenames that start with "access.log" in the current directory.

Answer 47

ls acc*

Question 48

How would you find all files in the current directory and all subdirectories that are of the type "file"?

Answer 48

ls . -type f

Question 49

How do you print all the files in the current and subdirectories that have the word "access" in the filename and the text "500" in them?

Answer 49

find -name "access*" -exec grep -h '500' { } \;

Question 50

Extract all IP addresses from files (recursively, all subdirectories) that start with "access.log" printing one IP address per line.

Answer 50

find . -type f -name "access.log*" -exec grep -oE

Question 51

Regex for IP address?

Answer 51

([0-9]{1,3}\.)[0-9]{1,3}

Question 52

Extract all IP addresses from files that start with "access.log" printing one IP address per line.

Answer 52

find . -type f -iname "access.log*" -exec grep -Eo "([0-9]{1,3}\.){3}[0-9]{1,3}" {} \;

Question 53

How would you print the files in the current directory that have the text "John Williams" but NOT "John Williamson" in all text files?

Answer 53

grep -w "John Williams" *.txt

Question 54

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files?

Answer 54

grep -wi "John Williams" *.txt

Question 55

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on?

Answer 55

grep -win "John Williams" *.txt

Question 56

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on, AND all the text that appears 4 lines before the searched text?

Answer 56

grep -win -B 4 "John Williams" *.txt

Question 57

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on, AND all the text that appears 4 lines after the searched text?

Answer 57

grep -win -A 4 "John Williams" *.txt

Question 58

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on, AND all the text that appears 4 lines BEFORE and AFTER the searched text?

Answer 58

grep -win -C 4 "John Williams" *.txt

Question 59

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in every file in the current directory, and what line the text appears on?

Answer 59

grep -win "John Williams" ./*

Question 60

How would you print the files in the current directory and all subdirectories (recursively) that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on, AND all the text that appears 4 lines BEFORE and AFTER the searched text?

Answer 60

grep -winr "John Williams" .

Question 61

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on, AND all the text that appears 4 lines BEFORE and AFTER the searched text? Just print the path and file name and not the text in the file with a a match?

Answer 61

grep -wirl "John Williams" .

Question 62

How would you print the files in the current directory that have the text "John Williams" and "john williams", but NOT "John Williamson" in all text files, and what line the text appears on, AND all the text that appears 4 lines BEFORE and AFTER the searched text? Just print the path and file name and number of matches in each file, and not the text in the file with a a match?

Answer 62

grep -wirc "John Williams" .

Question 63

Delete all of the files in the current directory including all subdirectories and their contents?

Answer 63

find . -mindepth 1 -delete

Question 64

How do you count the number of files in the current working directory?

Answer 64

ls -l | wc -l

Question 65

Print all files in the current directory, one per line (not the path, just the filename) that contain the string "500".

Answer 65

grep 500 -lhr

Question 66

Delete all of the files in this challenge directory including all subdirectories and their contents.

Answer 66

find . -delete

Question 67

Count the number of files in the current working directory. Print the number of files as a single integer.

Answer 67

ls -l | wc -l

Question 68

Print the number of lines in access.log that contain the string "GET".

Answer 68

cat access.log | grep "GET" | wc -l

Question 69

The file split-me.txt contains a list of numbers separated by a ';' character. Split the numbers on the ';' character, one number per line.

Answer 69

cat access.log | tr

Question 70

Print the numbers 1 to 100 separated by spaces.

Answer 70

echo {1..100}

Question 71

There are files in this challenge with different file extensions. Remove all files with the .doc extension recursively in the current working directory.

Answer 71

find . -type f -name "*.doc" -delete

Question 72

The file sum-me.txt has a list of numbers, one per line. Print the sum of these numbers.

Answer 72

awk 'BEGIN { sum=0 } { sum+=$1 } END { print sum }' sum-me.txt

Question 73

Print all files in the current directory recursively without the leading directory path.

Answer 73

ls -R | grep [A-z]

Question 74

The file split-me.txt contains a list of numbers separated by a ';' character. Split the numbers on the ';' character, one number per line.

Answer 74

tr ";" "\n"