LPIC-1 Shells, Scripting and Data Management — 20 Questions

Question 1

A system administrator writes a script that extracts data from a CSV file and inserts it into a database. The script works correctly when run manually but fails when executed by cron. Which environment variable is most likely causing the issue?

Accepted Answer

PATH. When a script runs manually, the user's interactive shell inherits a fully populated PATH environment variable that includes directories like /usr/local/bin, /usr/bin, and possibly custom script directories. Cron jobs, however, execute with a minimal environment, and the default PATH for cron is often just /usr/bin:/bin. If the script relies on commands (e.g., mysql, psql, or custom scripts) located outside these directories, cron will fail with a 'command not found' error. Setting the full PATH explicitly inside the script or in the crontab file resolves the issue.

Answer

SHELL

Answer

LANG

Answer

HOME

Question 2

A developer needs to ensure a bash script exits immediately if any command fails, and also prints each command before executing it. Which set of shell options should be used at the beginning of the script?

Accepted Answer

set -ex. Option A is correct because `set -ex` combines two essential shell options: `-e` (errexit) causes the script to exit immediately if any command returns a non-zero exit status, and `-x` (xtrace) prints each command (after expansion) to stderr before executing it. This is the standard way to achieve both behaviors in a single line, as required by the question.

Answer

set -e

Answer

set -vx

Answer

set -ux

Question 3

A script contains the following line: for i in $(cat file.txt); do echo $i; done. The file file.txt contains a single line with multiple words. How many times will the loop execute?

Accepted Answer

Equal to the number of words in the file. The command substitution $(cat file.txt) expands to the content of file.txt, which is a single line with multiple words. The for loop iterates over each word (separated by whitespace) in the expanded string, not over lines. Therefore, the loop executes once per word in the file.

Answer

Equal to the number of lines in the file

Answer

Once

Answer

The loop will not execute

Question 4

Refer to the exhibit. Why does the cron job fail?

Accepted Answer

The script is not executable.. C is correct because cron jobs require the script to be executable (i.e., have the execute permission bit set). If the script is not executable, cron will fail to run it even if the shebang line and PATH are correct. The error typically appears in the cron log or as a silent failure.

Answer

The cron job lacks the PATH environment variable.

Answer

The script is owned by root, but the cron job runs as a different user.

Answer

The script lacks a shebang line.

Question 5

Which TWO commands can be used to sort the output of ps -ef by the resident set size (RSS) in descending order?

Accepted Answer

ps --sort=-rss. Option B is correct because `ps --sort=-rss` directly sorts the process list by resident set size (RSS) in descending order, using the minus sign prefix to indicate reverse sort. This is a native `ps` feature that avoids piping to `sort`, which can be less reliable due to column alignment issues.

Answer

ps -ef | sort -k5,5 -rn

Answer

ps -ef | sort -k3 -rn

Answer

ps --sort=rss

Question 6

Which THREE statements are true about the sed command?

Accepted Answer

sed -i 's/foo/bar/g' file.txt replaces all occurrences of foo with bar in the file.. Option B is correct because the `-i` flag in sed enables in-place editing, directly modifying the file rather than just outputting changes to stdout. The substitution command `'s/foo/bar/g'` replaces all occurrences of `foo` with `bar` globally on each line, and with `-i`, the changes are written back to the file.

Answer

sed 's/old/new/g' file.txt permanently changes the file.

Answer

sed uses extended regular expressions by default.

Question 7

A cron job is configured to run a script every day at 2:30 AM. The sysadmin notices the job runs but produces no output. Which is the most likely reason?

Accepted Answer

The MAILTO environment variable is not set, and the output is not redirected.. Option C is correct because cron jobs run in a non-interactive, non-terminal environment. By default, cron captures any output (stdout/stderr) from the job and attempts to email it to the user. If the MAILTO variable is not set and the output is not redirected to a file or /dev/null, the output is simply discarded, resulting in no visible output. The job still runs successfully, but the output is lost.

Answer

The cron daemon is not running.

Answer

The script requires a terminal to run.

Answer

Cron automatically suppresses all output.

Question 8

A systems administrator is responsible for a Linux server that runs a custom application. The application writes logs to /var/log/app.log and rotates them using logrotate. Recently, the server ran out of disk space because log files were not being rotated. The administrator checks the logrotate configuration file /etc/logrotate.d/app and finds:

/var/log/app.log {
    weekly
    rotate 4
    compress
    missingok
    notifempty
}

The administrator manually runs 'logrotate -f /etc/logrotate.d/app' and the log rotates successfully. However, the next day, the log is not rotated again. The administrator checks the cron job for logrotate and finds that /etc/cron.daily/logrotate exists and runs logrotate /etc/logrotate.conf. The administrator checks /etc/logrotate.conf and sees that it includes /etc/logrotate.d/*. What is the most likely reason the log is not rotating automatically?

Accepted Answer

The 'notifempty' directive is misspelled; it should be 'notifempty'.. Option B is correct because the 'notifempty' directive is misspelled as 'notifempty' (it should be 'notifempty'). Logrotate silently ignores unknown directives, so the misspelled directive has no effect. Without the correct 'notifempty' directive, logrotate will skip rotation if the log file is empty, which can prevent rotation from occurring automatically even though the manual forced rotation with -f succeeds.

Answer

The 'weekly' directive is misspelled.

Answer

The /etc/logrotate.d/ directory is not included by logrotate.conf.

Answer

The 'missingok' directive prevents rotation if the log file is missing, but the file exists.

Question 9

A system administrator needs to ensure that a bash script continues executing even if any command in the script fails. Which of the following should be used at the beginning of the script?

Accepted Answer

set +e. Option A is correct because `set +e` disables the 'exit on error' behavior in a bash script, allowing the script to continue executing even if a command returns a non-zero exit status. By default, bash scripts do not exit on error, but if `set -e` is used elsewhere, `set +e` explicitly turns that off to ensure the script continues despite failures.

Answer

trap 'echo error' ERR

Answer

unset -e

Answer

set -e

Answer

# set +e

Question 10

Which TWO commands can be used to count the number of lines in a file named 'data.txt'?

Accepted Answer

wc -l data.txt. Option A is correct because `wc -l` specifically counts the number of newline characters in the file, which corresponds to the number of lines. Option B is correct because `awk 'END{print NR}'` processes the file line by line, and the built-in variable `NR` holds the total number of records (lines) processed when the END block is executed, thus outputting the line count.

Answer

cat data.txt | wc -c

Answer

grep -c '.*' data.txt

Answer

sed -n '$=' data.txt

Question 11

A user reports that running '/usr/local/bin/myapp' from the command line results in 'bash: /usr/local/bin/myapp: No such file or directory'. The exhibit shows the file exists and is a valid executable. What is the most likely cause of the error?

Accepted Answer

The dynamic linker /lib64/ld-linux-x86-64.so.2 is missing or corrupted.. When a dynamically linked executable exists and is valid but fails with 'No such file or directory', the most common cause is that the dynamic linker (e.g., /lib64/ld-linux-x86-64.so.2) is missing or corrupted. Bash reports this error because the kernel's execve() syscall cannot find the interpreter specified in the ELF's PT_INTERP segment, not because the executable itself is absent. This is a classic symptom distinct from a missing library, which would produce 'error while loading shared libraries'.

Answer

The script interpreter specified in the shebang is missing.

Answer

The library libc.so.6 is missing.

Answer

The file does not have execute permission for the user.

Question 12

Order the steps to add a new user to the system and grant sudo privileges.

Question 13

Match each package manager to its associated distribution family.

Question 14

An administrator wants to list all lines in a log file that do NOT contain the word 'ERROR'. Which command should be used?

Accepted Answer

grep -v 'ERROR' logfile. Option C is correct because the -v option in grep inverts the match, showing lines that do not contain ERROR. Option A shows lines containing ERROR. Option B is also -v? Wait, we moved correct to C.

Answer

grep -i 'ERROR' logfile

Answer

grep -w 'ERROR' logfile

Answer

grep 'ERROR' logfile

Question 15

In a bash script, a variable 'file' is set to '/var/log/syslog'. Which expansion will yield the string '/var/log'?

Accepted Answer

${file%/*}. Option C is correct because the `${file%/*}` expansion uses the `%` operator to remove the shortest suffix matching the pattern `/*`, which matches the last slash and everything after it. Since `file` is `/var/log/syslog`, this removes `/syslog`, leaving `/var/log`. This is a standard parameter expansion in bash for stripping a trailing path component.

Answer

${file##*/}

Answer

${file%%/*}

Answer

${file#*/}

Question 16

A script uses a while loop to read lines from a file, but a variable set inside the loop is empty after the loop finishes. What is the most likely cause?

Accepted Answer

The while loop is part of a pipeline, causing it to run in a subshell.. Option B is correct because if the while loop is part of a pipeline, it runs in a subshell and variable changes are not visible to the parent.

Answer

The file has an empty line at the end.

Answer

The variable is declared as readonly.

Answer

The variable name contains spaces.

Question 17

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. Option D is correct because 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 18

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. Option A is correct because 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 19

A script uses a here-document to pass multi-line input to a command. Which here-document syntax will prevent variable expansion inside the document?

Accepted Answer

<< 'EOF'. Option D is correct because single-quoting the delimiter (e.g., `<< 'EOF'`) prevents the shell from performing variable expansion and command substitution within the here-document. The shell treats the quoted delimiter literally, so all content between the start and end markers is passed verbatim to the command.

Answer

<< EOF

Answer

<<- EOF

Answer

<< "EOF"

Question 20

Which command combination will display a sorted list of unique lines from a file?

Accepted Answer

Both A and C. Option D is correct because both A and C produce a sorted list of unique lines from a file. In option A, `cat file | uniq | sort` first removes adjacent duplicates with `uniq`, then sorts the remaining lines, which yields a sorted unique list only if the file was already sorted. In option C, `cat file | sort | uniq` sorts the file first, then removes all duplicate lines (adjacent after sorting), guaranteeing a sorted unique list. Option B (`sort -u file`) also produces a sorted unique list, but it is not part of the combination asked for in the question.

Answer

cat file | uniq | sort

Answer

sort -u file

Answer

cat file | sort | uniq