Command Parser: Parse and Dispatch Shell-Like Commands from User Input
Interview Experience
Round 1 Coding / OOD
Problem
Design a command parser that reads a command string from the user, parses it into a command name and arguments, and dispatches it to a registered handler. Support flags (e.g., --verbose) and named arguments (e.g., --output=file.txt).
python
class CommandParser:
def register(self, name: str, handler: callable,
description: str = "") -> None:
...
def parse(self, input_str: str) -> dict:
**returns** {"command": str, "args": list, "flags": set, "kwargs": dict}
...
def execute(self, input_str: str) -> any:
...
def help(self) -> str:
...
Example
parser = CommandParser()
parser.register("greet", lambda args, **kw: f"Hello, {args[0]}!")
parser.register("add", lambda args, **kw: sum(int(a) for a in args))
parser.execute("greet Alice --verbose")
# parse -> {"command":"greet","args":["Alice"],"flags":{"verbose"},"kwargs":{}}
# -> "Hello, Alice!"
parser.execute("add 1 2 3 --output=result.txt")
# -> 6, and kwargs has output="result.txt"
parser.execute("unknown")
# -> raises UnknownCommandError
Follow-ups
- How do you handle quoted arguments with spaces, like
greet "Alice Smith"? - How would you add argument type coercion so a handler can declare it expects integers?
- How would you add tab-completion support for registered command names?
- How does your design change if you need to support chaining commands with pipes, like
list | filter --active?
Full Details
Round 1 Coding / OOD
Problem
Design a command parser that reads a command string from the user, parses it into a command name and arguments, and dispatches it to a registered handler. Support flags (e.g., --verbose) and named arguments (e.g., --output=file.txt).
python
class CommandParser:
def register(self, name: str, handler: callable,
description: str = "") -> None:
...
def parse(self, input_str: str) -> dict:
**returns** {"command": str, "args": list, "flags": set, "kwargs": dict}
...
def execute(self, input_str: str) -> any:
...
def help(self) -> str:
...
Example
parser = CommandParser()
parser.register("greet", lambda args, **kw: f"Hello, {args[0]}!")
parser.register("add", lambda args, **kw: sum(int(a) for a in args))
parser.execute("greet Alice --verbose")
# parse -> {"command":"greet","args":["Alice"],"flags":{"verbose"},"kwargs":{}}
# -> "Hello, Alice!"
parser.execute("add 1 2 3 --output=result.txt")
# -> 6, and kwargs has output="result.txt"
parser.execute("unknown")
# -> raises UnknownCommandError
Follow-ups
- How do you handle quoted arguments with spaces, like
greet "Alice Smith"? - How would you add argument type coercion so a handler can declare it expects integers?
- How would you add tab-completion support for registered command names?
- How does your design change if you need to support chaining commands with pipes, like
list | filter --active?
About This Question
This is a candidate experience report from a samsara interview during the onsite round.
It covers the following topics: Coding, Ood, Strings, Onsite .
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About Samsara Interview Reports
This question was reported by a candidate who interviewed at Samsara. LeakCode aggregates interview reports from 10+ sources, including 1Point3Acres, Glassdoor, LeetCode Discuss, Blind, Reddit, Indeed, and Nowcoder. Each report is translated where necessary, deduplicated against existing entries, and tagged by company, role, round type, and reporting date.
Use this question as one calibration data point, not a memorization target. Companies typically rotate their question pools every 2-4 months; the exact wording of a 2024 question may differ from what you encounter today. The underlying pattern, difficulty level, and follow-up depth at Samsara are the higher-signal extractions to take from this report.
For broader preparation context, the Samsara interview process typically includes a recruiter screen, one or two technical phone screens, and a 4-5 round on-site loop covering coding, system design (at L4+ levels), and behavioral. Reports tagged on LeakCode show the round-by-round distribution and typical difficulty calibration. To browse questions filtered by round type and seniority, use the company hub linked above.
How To Practice This Type of Question
Solve similar problems on LeetCode under timed conditions (25-35 minutes per medium difficulty). The goal is pattern recognition: recognize the underlying technique (sliding window, two-pointer, BFS, memoized recursion, etc.) within 60-90 seconds of reading. Strong candidates verbalize their hypothesis out loud before coding, then iterate based on feedback. Weak candidates dive into implementation immediately, lose time on the wrong approach, and run out of time for follow-ups.
Companies update their question pools every 2-4 months. The exact wording of any given question may have been retired by the time you interview. Focus your prep on the pattern, not the specific problem. The patterns that appear in Samsara reports consistently are the ones worth investing in; one-off niche problems are not.
During Your Samsara Round
Apply the standard interview round template: clarify requirements (2-3 minutes), state your approach out loud and confirm direction with the interviewer (3-5 minutes), code with narration (15-25 minutes), test with concrete examples including edge cases (5 minutes), discuss optimization or trade-offs if time permits (5 minutes). This template is universally accepted across FAANG and adjacent companies; deviating from it produces weaker interviewer feedback signal.
The single most predictive failure mode in Samsara reports tagged "no hire": not asking clarifying questions. Interviewers are explicitly trained to weight this. Strong candidates ask 3-5 clarifying questions even on problems that look obvious; weak candidates dive into code immediately. The clarifying-question check is often the first signal recorded in the interviewer's written notes.