LPIC-1 Shells, Scripting and Data Management Practice Test 4 — 15 Questions

Question 1

Which sed command will replace the first occurrence of 'foo' with 'bar' on each line of a file?

Accepted Answer

sed 's/foo/bar/' file. The default behavior of the `s` (substitute) command in sed is to replace only the first occurrence of the pattern on each line. Without a numeric flag, `sed 's/foo/bar/' file` replaces the first 'foo' on each line with 'bar'. The `g` flag would replace all occurrences, not just the first.

Answer

sed 's/foo/bar/g' file

Answer

sed 's/foo/bar/0' file

Answer

sed 's/foo/bar/2' file

Question 2

Given a file with lines like 'John:23:Engineer', which awk command prints only the name and department (first and third fields) separated by a space?

Accepted Answer

awk -F: '{print $1,$3}' file. The `-F:` flag sets the field separator to colon, and `{print $1,$3}` prints the first and third fields separated by the default output field separator (a space). This matches the requirement to output the name and department from lines like 'John:23:Engineer'.

Answer

awk -F: '{print $1,$2}' file

Answer

awk -F: '{print $1 $3}' file

Answer

awk -F: '{print $1 $2}' file

Question 3

A script reads a CSV file where fields may contain commas within quoted strings. Which approach correctly parses such fields?

Accepted Answer

Using awk or a dedicated tool like csvkit. CSV fields containing commas within quoted strings require a parser that understands CSV quoting rules. Awk can be scripted to handle quoted fields, and dedicated tools like csvkit (e.g., csvcut, csvformat) are designed specifically to parse CSV according to RFC 4180, correctly ignoring commas inside double-quoted strings.

Answer

Using 'cut -d',' -f1,2 file'

Answer

Using 'while IFS= read -r line; do ... done < file' and parsing manually

Answer

Using 'while IFS=',' read -r f1 f2; do ... done < file'

Question 4

Which TWO of the following are true about the 'source' command in bash?

Accepted Answer

It can be abbreviated as '.' (dot).. Option C is correct because the dot command (.) is the POSIX-standard abbreviation for source, so `source file` and `. file` are equivalent in bash. Option D is correct because source reads and executes the script's commands in the current shell environment, which is why variables and functions defined in the sourced file persist in the calling shell. Option A is wrong because executing in a subshell is what happens when you run a script normally (e.g., `bash script.sh` or `./script.sh`), not when sourcing it. Option B is wrong because the dot form is specified by POSIX and works in POSIX sh, even though the name `source` itself is a bash extension. Option E is wrong because source reads the file with the shell, so the script only needs read permission, not execute permission.

Answer

It executes a script in a subshell.

Answer

It is only available in bash and not in POSIX sh.

Answer

It requires the script to have execute permission.

Question 5

Refer to the exhibit. An administrator installed a new command in /opt/bin/ but cannot run it without specifying the full path. What is the likely cause?

Accepted Answer

The command is not in the PATH.. The administrator installed the command in /opt/bin/, but the shell cannot find it without the full path because /opt/bin/ is not listed in the PATH environment variable. The PATH variable defines the directories the shell searches for executable commands; if a directory is omitted, commands within it must be invoked with an absolute or relative path.

Answer

The command is an alias that conflicts.

Answer

The command has no execute permission.

Answer

The command is a function that overrides.

Question 6

Refer to the exhibit. When will the cron job execute?

Accepted Answer

Every minute.. The cron job entry `* * * * *` specifies five fields (minute, hour, day of month, month, day of week), each set to `*`, meaning 'every'. This results in the job executing every minute of every hour, every day of the month, every month, and every day of the week — i.e., every minute without restriction.

Answer

Every minute of every hour, but only weekdays.

Answer

Every day at midnight.

Answer

Every hour.

Question 7

A system administrator wants to display all lines in /var/log/syslog that do NOT contain the string 'error'. Which command accomplishes this?

Accepted Answer

grep -v 'error' /var/log/syslog. The `grep -v` option inverts the match, displaying only lines that do NOT contain the pattern. Therefore, `grep -v 'error' /var/log/syslog` outputs all lines from the file that lack the string 'error', which directly fulfills the requirement.

Answer

grep -r 'error' /var/log/syslog

Answer

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

Answer

grep -i 'error' /var/log/syslog

Question 8

A script produces both standard output and error messages. An administrator wants to save the output to 'out.log' and the error messages to 'err.log', but also wants to see both on the terminal. Which command achieves this?

Accepted Answer

./script.sh > >(tee out.log) 2> >(tee err.log). Uses process substitution to redirect stdout and stderr into separate tee commands, which both write to files and pass the streams through to the terminal. The syntax `> >(tee out.log)` redirects stdout to a tee process that writes to out.log and also echoes to the terminal, while `2> >(tee err.log)` does the same for stderr. This ensures both streams are saved to separate files and displayed on the terminal simultaneously.

Answer

./script.sh 2>&1 | tee out.log 2>&1 | tee err.log

Answer

./script.sh > out.log 2> err.log

Answer

./script.sh 2>&1 | tee out.log

Question 9

An administrator needs to replace all occurrences of 'old_host' with 'new_host' in the file /etc/hosts. Which sed command should be used?

Accepted Answer

sed -i 's/old_host/new_host/g' /etc/hosts. The `-i` flag enables in-place editing of the file, and the `g` flag (global) ensures all occurrences on each line are replaced, not just the first. The command `sed -i 's/old_host/new_host/g' /etc/hosts` modifies the file directly, replacing every instance of 'old_host' with 'new_host' throughout the file.

Answer

sed -n 's/old_host/new_host/gp' /etc/hosts

Answer

sed -i 's/old_host/new_host/' /etc/hosts

Answer

sed 's/old_host/new_host/g' /etc/hosts

Question 10

A directory contains files with spaces and special characters in their names. An administrator wants to delete all files older than 30 days using find and xargs. Which command is safe?

Accepted Answer

find /path -type f -mtime +30 -print0 | xargs -0 rm. It uses `-print0` with `find` to output null-delimited filenames, and `xargs -0` to process them safely. This handles spaces, newlines, and special characters in filenames without word-splitting or shell interpretation, ensuring all matching files older than 30 days are deleted reliably.

Answer

find /path -type f -mtime +30 -delete

Answer

find /path -type f -mtime +30 -exec rm {} \;

Answer

find /path -type f -mtime +30 | xargs rm

Question 11

A script starts multiple background processes. An administrator wants to wait for all background jobs to complete before proceeding. Which command should be used?

Accepted Answer

wait. The `wait` command without any arguments waits for all background jobs spawned by the current shell to complete before returning control to the script. This is the correct way to synchronize multiple background processes in a shell script, ensuring all child processes finish before proceeding to the next command.

Answer

jobs -l

Answer

wait %1

Answer

sleep 5

Question 12

Refer to the exhibit. An administrator runs this command expecting to capture both stdout and stderr into output.txt. However, the file contains only stdout. What is the error?

Accepted Answer

The 2>&1 should appear after the > output.txt.. The error is that the `2>&1` redirection appears before the `> output.txt` on the command line. In bash, redirections are evaluated left to right. When `2>&1` is placed first, it redirects stderr (file descriptor 2) to the current target of stdout (file descriptor 1), which at that point is still the terminal, not the file. The subsequent `> output.txt` redirects only stdout to the file, leaving stderr still going to the terminal. To capture both, `2>&1` must appear after `> output.txt`, so that stderr is redirected to the file descriptor that now points to the file.

Answer

The file already exists and is not writable.

Answer

The stdout redirection should be 1> instead of >.

Answer

The command must be run as root.

Question 13

Refer to the exhibit. An administrator wants to unset the BASH_ALIASES associative array. Which command will correctly remove it?

Accepted Answer

unset BASH_ALIASES. `unset` is the standard Bash built-in command to destroy a variable or function. For an associative array like BASH_ALIASES, `unset BASH_ALIASES` removes the entire array, including all its key-value pairs, from the current shell environment.

Answer

export -n BASH_ALIASES

Answer

unset -v BASH_ALIASES

Answer

delete BASH_ALIASES

Question 14

A user needs to schedule a backup script to run every weekday at 2:00 AM. Which command should they use to set up this recurring job?

Accepted Answer

crontab -e and add a line. The cron daemon is the standard Linux tool for scheduling recurring jobs at specific times. Using `crontab -e` allows the user to edit their personal crontab file and add a line like `0 2 * * 1-5 /path/to/backup.sh` to run the script every weekday (Monday through Friday) at 2:00 AM.

Answer

sleep 3600 && ./backup.sh

Answer

at -f backup.sh 2:00

Answer

batch

Question 15

A shell script uses the variable expansion ${var:-default} to set a default value for an environment variable. The script prints unexpected output when the variable is set to an empty string. Which expansion should be used to ensure the default is only used when the variable is unset, not when it is empty?

Accepted Answer

${var-default}. The expansion `${var-default}` uses the default value only when the variable is unset (i.e., does not exist at all). In contrast, `${var:-default}` also substitutes the default when the variable is set but empty, which causes the unexpected output described in the question. The colon in the expansion is the critical difference: it adds the check for a null or empty string.

Answer

${var:-default}

Answer

${var:?default}

Answer

${var:=default}