Quick Answer
The correct pipe command is | tail 10, because Junos uses Unix-style pipe filters, and 'tail' is the proper keyword to display the last N lines of output from a command like 'show log messages'. Unlike the generic 'last' command, which is not recognized by the Junos CLI pipe system, 'tail' directly mirrors the behavior of the Unix tail utility, allowing you to view the final lines of any log file or command output. On the JNCIA-Junos exam, this question tests your familiarity with common pipe filters, a frequent topic in the Junos CLI fundamentals section, and it often traps candidates who assume 'last' is a valid pipe option. A helpful memory tip is to think of the Unix command you would use on a Linux system to view the end of a file—it is always 'tail', never 'last', and Junos follows the same convention.
This JNCIA-JUNOS practice question tests your understanding of user interfaces. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A junior network engineer is learning JunOS CLI and wants to view the last 10 lines of the system log file. They log into the device and type 'show log messages | last 10'. They receive an error: 'unknown pipe command'. Which pipe command should they use instead?
| last 10
Why wrong: This is not a valid pipe command; it caused the error.
| display 10
Why wrong: There is no 'display' pipe command for showing a specific number of lines.
| head 10
Why wrong: This displays the first 10 lines, not the last.
| tail 10
The '| tail' pipe command displays the last N lines of output.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
| tail 10
In JunOS CLI, the pipe command to display the last N lines of output is '| tail N', not '| last N'. The 'tail' command filters the output to show only the final lines, analogous to the Unix 'tail' utility. Option D is correct because '| tail 10' will show the last 10 lines of the system log file.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
| last 10
Why it's wrong here
This is not a valid pipe command; it caused the error.
| display 10
Why it's wrong here
There is no 'display' pipe command for showing a specific number of lines.
| head 10
Why it's wrong here
This displays the first 10 lines, not the last.
| tail 10
Why this is correct
The '| tail' pipe command displays the last N lines of output.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates familiar with Cisco IOS may expect '| last 10' to work, but JunOS uses Unix-style pipe commands where 'tail' is the correct filter for displaying the end of output.
Trap categories for this question
Command / output trap
This is not a valid pipe command; it caused the error.
Detailed technical explanation
JunOS pipe commands are processed by the management daemon (mgd) and include standard Unix-like filters such as 'tail', 'head', 'match', 'count', and 'except'. The 'tail' command supports options like '| tail -f' for real-time log monitoring, which is useful for troubleshooting live events. Understanding these filters is essential for efficient CLI navigation and log analysis in production environments.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the JNCIA-JUNOS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
The correct answer is: | tail 10 — In JunOS CLI, the pipe command to display the last N lines of output is '| tail N', not '| last N'. The 'tail' command filters the output to show only the final lines, analogous to the Unix 'tail' utility. Option D is correct because '| tail 10' will show the last 10 lines of the system log file.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the JNCIA-JUNOS exam.
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