010-160 The Power OF The Command Line Practice Test 1 — 15 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

You have a compressed file 'data.tar.bz2'. Which flag is needed to extract it?

Accepted Answer

tar -xjf data.tar.bz2. The -j flag tells tar to filter the archive through bzip2 for decompression, which is required for .tar.bz2 files. Combined with -x (extract) and -f (file), the correct invocation is tar -xjf data.tar.bz2. Without -j, tar would not know the compression algorithm and would fail or produce garbage output.

Answer

tar -xzf data.tar.bz2

Answer

tar -xAf data.tar.bz2

Answer

tar -xvf data.tar.bz2

Question 5

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 6

What is the purpose of the 'tee' command?

Accepted Answer

To split output to both screen and file.. The 'tee' command reads from standard input and writes to both standard output (typically the terminal) and one or more files simultaneously. This allows you to view command output in real time while also saving it to a file for later analysis. It is commonly used in pipelines, e.g., 'command | tee output.log', to capture intermediate results without losing the ability to see them on screen.

Answer

To format text columns.

Answer

To terminate a process.

Answer

To compress files.

Question 7

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 8

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 9

Which THREE of the following are valid flags for the 'tar' command?

Accepted Answer

-z. Option B (-z) is correct because it tells tar to filter the archive through gzip, which is essential for creating or extracting .tar.gz/.tgz files. Option C (-x) is correct because it is the extract flag, instructing tar to extract files from an archive. Option D (-c) is correct because it is the create flag, used to build a new archive from the specified files. The unmarked options do not belong: -q is not a standard tar flag (quiet behavior is typically handled differently or via other tools), and while -p is a real tar flag for preserving permissions, it is not among the three answers marked correct here.

Answer

-q

Answer

-p

Question 10

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 11

While troubleshooting a server, you run `grep -r 'timeout' /etc/nginx/` and receive output that includes the filename and line number for every match. You now need to count only the total number of matching lines across all files, without displaying the matches themselves. Which command pipeline or option achieves this?

Accepted Answer

grep -r 'timeout' /etc/nginx/ | wc -l. Piping recursive grep output to wc -l counts matching lines across all files, which is the total required. The -c option counts per file, -l lists filenames, and -o counts individual occurrences, none of which gives the overall line total.

Answer

grep -l -r 'timeout' /etc/nginx/ | wc -l

Answer

grep -o -r 'timeout' /etc/nginx/ | wc -l

Answer

grep -c -r 'timeout' /etc/nginx/

Question 12

A user wants to count how many lines in the file /var/log/syslog contain the word 'error'. Which command accomplishes this?

Accepted Answer

grep -c 'error' /var/log/syslog. The grep command with -c counts matching lines directly. Alternatives that pipe to wc -l may produce the same number but are less straightforward; using wc -c counts bytes, and wc -l on the whole file counts all lines, not just matching ones. The direct grep -c is the correct, efficient tool.

Answer

cat /var/log/syslog | grep 'error' | wc -c

Answer

wc -l /var/log/syslog | grep 'error'

Answer

grep -n 'error' /var/log/syslog | wc -l

Question 13

You are working in a directory containing a file named `report.txt`. You want to make a copy of this file named `report_backup.txt` in the same directory. Which command accomplishes this?

Accepted Answer

cp report.txt report_backup.txt. The cp command is designed to copy files, preserving the original. mv renames or moves, ln creates links, and using cat with redirection, while possible, is not the standard file copy method.

Answer

ln report.txt report_backup.txt

Answer

cat report.txt > report_backup.txt

Answer

mv report.txt report_backup.txt

Question 14

A developer runs a program that writes progress messages to standard error and results to standard output. They want to save only the results to results.txt while still seeing progress messages on the terminal. Which redirection accomplishes this?

Accepted Answer

program > results.txt. Only the plain `>` redirection sends standard output to the file while leaving standard error attached to the terminal. Operators like `2>`, `&>`, and `> file 2>&1` either redirect the wrong stream or merge both streams, which would hide progress messages from the terminal.

Answer

program 2> results.txt

Answer

program > results.txt 2>&1

Answer

program &> results.txt

Question 15

You are examining a shell script and see the line `find /var/log -type f -name '*.log' -exec rm {} \;`. You want to modify this command so that it deletes matching files in a single rm invocation for better performance, while still handling filenames with spaces correctly. Which change should you make?

Accepted Answer

Replace -exec rm {} \; with -exec rm {} +. Using -exec with a plus terminator groups filenames into a single rm command, improving performance and correctly handling spaces. The other options either use incorrect syntax, change the deletion method, or add interactivity.

Answer

Replace -exec rm {} \; with -ok rm {} \;

Answer

Replace -exec rm {} \; with -exec rm {} \+

Answer

Replace -exec rm {} \; with -delete