010-160 The Power OF The Command Line Practice Test 3 — 15 Questions

Question 1

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 builtin marks a shell variable for inclusion in the environment of subsequently executed child processes. Writing export MYVAR=hello both assigns the value and exports it in one step, making it visible to programs launched from that shell. Without export, the variable would remain a shell-local variable and would not be inherited by child processes.

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set MYVAR=hello

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MYVAR=hello

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env MYVAR=hello

Question 2

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 `-czf` flag combination in `tar` specifies: `-c` to create a new archive, `-z` to filter the archive through gzip for compression, and `-f` to specify the archive filename. This directly produces a gzip-compressed tarball named `docs.tar.gz` from the `/home/user/docs` directory. The `-z` flag is the key to invoking gzip compression, which is exactly what the question asks for.

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

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

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

Question 3

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

Accepted Answer

It lists only directories in the current directory.. The command 'ls -la | grep "^d"' lists all files and directories in long format, including hidden ones, and then filters the output to show only lines starting with 'd', which indicates a directory. Thus, it lists only directories in the current directory.

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It shows only hidden files.

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It lists files that contain the letter 'd'.

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It deletes all directories.

Question 4

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

Accepted Answer

>>. The >> operator redirects standard output and appends it to the end of an existing file, preserving the original content. This is the standard shell redirection for adding data without truncation. The single > would overwrite the file, and the other symbols perform input redirection or piping, not appending.

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<

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|

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>

Question 5

What does the command 'history' do?

Accepted Answer

It prints the command history list.. The 'history' command in Bash and other POSIX shells prints the numbered list of previously executed commands stored in the shell's history buffer (typically ~/.bash_history). It is a shell builtin, not an external binary, and it reads from the in-memory history list maintained per session. This is the standard way to review and recall prior commands for reuse or auditing.

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It shows the date and time of file creation.

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It displays the system log history.

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It deletes all previous command history.

Question 6

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 is purpose-built for filesystem traversal and can search by name, size, time, permissions, and more. Running `find / -name notes.txt` starts at the root directory and recursively descends every subdirectory, matching files whose basename is exactly 'notes.txt'. It is the most efficient and correct tool because it operates directly on directory entries via the kernel, without spawning extra processes per file.

Answer

grep -r notes.txt /

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search notes.txt /

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ls -R / | grep notes.txt

Question 7

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

Accepted Answer

Tab. Pressing the Tab key in a Linux shell triggers the readline completion feature, which autocompletes filenames, directory paths, and command names based on what you have typed so far. If multiple matches exist, pressing Tab twice lists all candidates. This is a core productivity shortcut in bash and most other shells.

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Enter

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Shift + Insert

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Ctrl + C

Question 8

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

Accepted Answer

export PATH=$PATH:/opt/bin. The export command marks a shell variable for inclusion in the environment of subsequently executed child processes, so 'export PATH=$PATH:/opt/bin' both appends /opt/bin to PATH and ensures the change propagates to child processes. This is the standard, portable way to modify PATH in bash and other POSIX shells. Without export, the change would remain local to the current shell.

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set PATH=$PATH:/opt/bin

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env PATH=$PATH:/opt/bin

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PATH=$PATH:/opt/bin

Question 9

If you want to view a long text file page by page, which command is most suitable?

Accepted Answer

less filename. The less command is a pager that displays a file one screenful at a time, allowing the user to scroll forward and backward with arrow keys, Page Up/Down, and search with '/'. It reads the file lazily and does not load the entire content into memory, making it ideal for viewing long text files interactively. This is the canonical tool for page-by-page file inspection on Linux.

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tail filename

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cat filename

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grep filename

Question 10

You want to find lines in 'file.txt' that do NOT contain the word 'success'. Which command works?

Accepted Answer

grep -v 'success' file.txt. The `-v` option inverts the match, so `grep -v 'success' file.txt` prints every line that does NOT contain the pattern 'success'. This is the standard way to filter out matching lines in Linux/Unix. The other options either show matching lines, count them, or ignore case, but none exclude them.

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grep -n 'success' file.txt

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grep -c 'success' file.txt

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grep -i 'success' file.txt

Question 11

Which symbol represents the current user's home directory in the shell?

Accepted Answer

~. The tilde symbol (~) is a shell metacharacter that expands to the absolute path of the current user's home directory (e.g., /home/username on Linux or /Users/username on macOS). It is recognized by the shell before command execution, so commands like cd ~ or ls ~/Documents work regardless of the current working directory. This is a standard feature in POSIX shells like Bash, Zsh, and Dash.

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.

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..

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$

Question 12

What is the result of 'echo $USER'?

Accepted Answer

It prints the current username.. $USER is a shell environment variable that holds the login name of the current user, so 'echo $USER' prints that username (e.g., 'alice'). The shell expands the variable before passing the argument to echo, so the literal string '$USER' is never printed.

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It prints the path to the user home.

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It returns an error.

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It prints '$USER'.

Question 13

Which command removes a directory and all its contents recursively?

Accepted Answer

rm -rf dir. rm -rf dir removes the directory and everything inside it recursively (-r) and forcibly (-f), without prompting. This is the standard command to delete a directory tree. The other options either don't exist, don't recurse, or only remove empty directories.

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rm -d dir

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del -r dir

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rmdir dir

Question 14

You want to execute two commands sequentially, but only if the first command succeeds. Which operator is used?

Accepted Answer

&&. The && operator is the logical AND control operator in Bash and other POSIX shells. It executes the command on the right only if the command on the left exits with a status of 0 (success). This is the standard way to chain commands with a success dependency, such as 'make && make install'.

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;

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||

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|

Question 15

You need to find files modified within the last 7 days. Which find flag is correct?

Accepted Answer

find . -mtime -7. The `-mtime -7` predicate matches files whose modification time is less than 7 days ago (i.e., within the last 7 days). The minus sign means 'less than N', so `-mtime -7` correctly captures recently modified files. This is the standard find syntax for time-based filtering and directly answers the requirement.

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find . -ctime 7

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find . -mtime +7

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find . -atime 7