010-160 The Power OF The Command Line — 25 Questions

Question 1

You have a large log file and want to view only the last 20 lines. Which command is best?

Accepted Answer

tail -n 20 logfile. tail is used to output the end part of a file; the -n option specifies the number of lines.

Answer

view -n 20 logfile

Answer

cat -n 20 logfile

Answer

head -n 20 logfile

Question 2

You want to combine the output of 'cat file1' and 'cat file2' and count the total number of lines in the result. Which pipe sequence is correct?

Accepted Answer

wc -l file1 file2. Piping joins commands; 'cat' sends data to 'wc -l' to count lines.

Answer

cat file1 + file2 | wc -l

Answer

cat file1 file2 > wc -l

Answer

cat file1 | cat file2 | wc -l

Question 3

You are using 'tar' and want to extract an archive named 'backup.tar.gz' into a specific directory named '/tmp/restore'. Which command is correct?

Accepted Answer

cd /tmp/restore && tar -xzf backup.tar.gz. The -C flag tells tar to change to the directory before performing the operation.

Answer

tar -xzf backup.tar.gz /tmp/restore

Answer

tar -xzf backup.tar.gz --dir /tmp/restore

Question 4

How do you redirect both standard output and standard error to a file named 'output.log'?

Accepted Answer

command > output.log 2>&1. The '>&' or '&>' syntax is commonly used in bash to redirect both streams.

Answer

command 1>2 output.log

Answer

command >> output.log

Question 5

Which command displays the first 5 lines of a file?

Accepted Answer

head -5 file. -n 5 specifies the number of lines for the head utility.

Answer

tail -n 5 file

Answer

cat -n 5 file

Question 6

Which command shows the manual page for 'ls'?

Accepted Answer

man ls. The man command displays system manual pages.

Answer

ls --doc

Answer

help ls

Question 7

Which TWO of the following are correct ways to set an environment variable?

Accepted Answer

export VAR=val. export command and assigning during command execution are valid.

Answer

assign VAR=val

Answer

set VAR=val

Answer

env -set VAR=val

Question 8

You want to find all occurrences of the string 'ERROR' within the 'syslog' file. Which command is most appropriate?

Accepted Answer

grep 'ERROR' syslog. grep is specifically designed to search for patterns within text files.

Answer

cat 'ERROR' syslog

Answer

find 'ERROR' syslog

Answer

sed 'ERROR' syslog

Question 9

Which command is used to display the current working directory in the terminal?

Accepted Answer

pwd. pwd stands for 'print working directory'.

Answer

dir

Answer

cd

Answer

ls

Question 10

You need to display the contents of a file named 'config.txt' directly to your terminal screen. Which command should you use?

Accepted Answer

cat config.txt. The cat command is the standard utility for concatenating and displaying file contents to standard output.

Answer

head config.txt

Answer

echo config.txt

Answer

grep config.txt

Question 11

You wish to send the output of the 'ls -l' command directly into a file named 'dirlist.txt', overwriting any existing content. Which operator should you use?

Accepted Answer

ls -l > dirlist.txt. The '>' operator redirects standard output to a file and overwrites it.

Answer

ls -l | dirlist.txt

Answer

ls -l >> dirlist.txt

Answer

ls -l < dirlist.txt

Question 12

You want to replace every occurrence of 'old' with 'new' in the file 'data.txt' and view the result in the terminal. Which command achieves this?

Accepted Answer

sed 's/old/new/g' data.txt. sed 's/old/new/g' replaces all instances of 'old' with 'new' globally in the stream.

Answer

sed 's/old/new/' data.txt

Answer

grep 's/old/new/g' data.txt

Answer

sed 'r/old/new/g' data.txt

Question 13

You need to set an environment variable named 'MYVAR' to 'hello' so that it is available to child processes. Which command is correct?

Accepted Answer

export MYVAR=hello. The export command is required to make an environment variable available to child shells.

Answer

set MYVAR=hello

Answer

MYVAR=hello

Answer

env MYVAR=hello

Question 14

You need to create a compressed archive of the '/home/user/docs' directory named 'docs.tar.gz'. Which flag ensures gzip compression is applied?

Accepted Answer

tar -czf docs.tar.gz /home/user/docs. The -z flag in tar invokes gzip compression for the archive.

Answer

tar -jf docs.tar.gz /home/user/docs

Answer

tar -xzf docs.tar.gz /home/user/docs

Answer

tar -cf docs.tar.gz /home/user/docs

Question 15

What is the result of the command 'ls -la | grep "^d"'?

Accepted Answer

It lists only directories in the current directory.. The '^d' pattern in grep filters for lines starting with 'd', which represents directories in long-format listings.

Answer

It shows only hidden files.

Answer

It lists files that contain the letter 'd'.

Answer

It deletes all directories.

Question 16

Which character is used to append output to an existing file without deleting its original content?

Accepted Answer

>>. The '>>' operator is the append redirection operator.

Answer

<

Answer

|

Answer

>

Question 17

What does the command 'history' do?

Accepted Answer

It prints the command history list.. It lists the commands previously executed in the current session.

Answer

It shows the date and time of file creation.

Answer

It displays the system log history.

Answer

It deletes all previous command history.

Question 18

You want to search for a file named 'notes.txt' starting from the root directory. Which command is most efficient?

Accepted Answer

find / -name notes.txt. The 'find' command searches the filesystem tree.

Answer

grep -r notes.txt /

Answer

search notes.txt /

Answer

ls -R / | grep notes.txt

Question 19

Which command-line shortcut allows you to autocomplete filenames and commands?

Accepted Answer

Tab. The Tab key is the standard shell completion mechanism.

Answer

Enter

Answer

Shift + Insert

Answer

Ctrl + C

Question 20

You need to change the environment variable PATH to include the directory '/opt/bin'. Which command is standard?

Accepted Answer

export PATH=$PATH:/opt/bin. Standard syntax involves referencing the current PATH and adding the new path.

Answer

set PATH=$PATH:/opt/bin

Answer

env PATH=$PATH:/opt/bin

Answer

PATH=$PATH:/opt/bin