Linux/UNIX file listing: Which command lists all files whose names end with the extension “.lst”, showing a detailed long listing for each match?

Difficulty: Easy

Correct Answer: ls -l .lst

Explanation:


Introduction / Context:
Command-line globbing patterns are crucial for filtering files by name. In Linux/UNIX shells, the asterisk * and other special characters expand to sets of filenames before the command runs. The ls utility then lists those files. Understanding which pattern truly selects files with a specific extension avoids accidental matches and incorrect outputs.


Given Data / Assumptions:

  • You want only filenames ending in “.lst”.
  • You also want a long listing (permissions, ownership, size, timestamps).
  • Globbing is performed by the shell, not by ls itself.


Concept / Approach:
The pattern “.lst” matches any file whose basename ends in the literal characters “.lst”. The ls -l flag produces a long listing. Other patterns here either select different names or are malformed for the stated goal. Therefore, “ls -l *.lst” precisely expresses “detailed listing of all .lst files.”


Step-by-Step Solution:

Identify the extension constraint: must end with “.lst”.Use the wildcard syntax: *.lst to match that suffix.Add -l to request long-format details.Run “ls -l *.lst” in the target directory.


Verification / Alternative check:
Run “echo *.lst” to see expanded matches. Compare “ls .lst” (short listing) versus “ls -l .lst” (long listing) to verify output differences.


Why Other Options Are Wrong:
ls lst: matches names beginning with “lst”, not ending in “.lst”. ls .: matches names with any dot, far broader than “.lst”. ls [lst]: matches names ending in one of the characters l, s, or t, not the string “.lst”. None of the above: incorrect because option A is correct.


Common Pitfalls:
Quoting the pattern (e.g., ".lst") prevents shell expansion when not desired; forgetting that hidden files (starting with a dot) are not matched by “” unless your shell option dotglob is set.


Final Answer:
ls -l *.lst

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