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Linux Foundation LFCS Exam - Topic 2 Question 53 Discussion

Actual exam question for Linux Foundation's LFCS exam
Question #: 53
Topic #: 2
[All LFCS Questions]

When running the command

sed -e "s/a/b/" /tmp/file >/tmp/file

While /tmp/file contains data, why is /tmp/file empty afterwards?

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Suggested Answer: D

by Refugia at Feb 06, 2023, 02:47 PM

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Jame
4 months ago
D is just wrong, redirection works with >, not just |.
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Lucy
5 months ago
B doesn't make sense, sed would still output something if it matched.
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Ludivina
5 months ago
Wait, are you saying the file gets overwritten before sed even runs? That's wild!
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Buck
5 months ago
Totally agree, C is the right answer here.
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Casie
5 months ago
It's all about the order of operations in shell commands!
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Reita
5 months ago
I don't think redirection works with the > character in this context. I remember something about using pipes instead, but I'm not confident about that.
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Truman
5 months ago
I recall reading that when you redirect output, the file gets overwritten right away. So, that might explain why /tmp/file is empty now.
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Genevieve
5 months ago
I'm not entirely sure, but I feel like I've seen a question like this before. Could it be that sed just didn't find anything to replace?
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Sheron
6 months ago
I think I remember something about the order of operations in shell commands. Maybe the output file gets cleared before sed even runs?
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Meaghan
6 months ago
Option D seems like the most comprehensive answer. It mentions that indexes can be removed or preserved, and that there are additional options to re-create the indexes after the load process. That sounds like the most flexible and configurable approach.
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Carlene
6 months ago
Hmm, I'm a bit unsure about this one. I'll need to review my notes on non-stop routing to see if I can identify the two correct characteristics.
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Jaclyn
11 months ago
Ah, the age-old question of why my output file is mysteriously empty. I bet the answer is hidden somewhere in the dark corners of the shell's arcane ways. Time to channel my inner shell wizard and figure this one out.
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Iluminada
9 months ago
C) When the shell establishes the redirection it overwrites the target file before the redirected command starts and opens it for reading.
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Dominga
10 months ago
B) The command sed did not match anything in that file therefore the output is empty.
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Ligia
10 months ago
A) The file order is incorrect. The destination file must be mentioned before the command to ensure redirection.
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Truman
11 months ago
Hold up, redirection doesn't work with the '>' character? Seriously? I guess I've been using the wrong tool for the job all this time. Time to brush up on my shell command-fu.
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Clorinda
11 months ago
I'm going with option C on this one. The shell is like a ninja, silently overwriting the target file before the command even has a chance to do its thing. Sneaky, but that's how it works.
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Kizzy
10 months ago
I see, so the shell takes care of the redirection before the command even starts. Good to know for future reference.
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Providencia
10 months ago
Yeah, that's right. The shell is quick to overwrite the target file before the command executes. It's important to keep that in mind when using redirection.
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Gail
10 months ago
I'm going with option C on this one. The shell is like a ninja, silently overwriting the target file before the command even has a chance to do its thing. Sneaky, but that's how it works.
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Alesia
11 months ago
Hmm, that makes sense too. Maybe we should review how sed works before the exam.
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Amber
11 months ago
Hmm, let's see... the file order is definitely not the issue here. And the sed command seems to be working fine, so it's not that either. Aha, I bet it's that sneaky overwrite that happens before the redirection kicks in! Gotta love those shell quirks.
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Norah
10 months ago
C) When the shell establishes the redirection it overwrites the target file before the redirected command starts and opens it for reading.
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Karima
11 months ago
A) The file order is incorrect. The destination file must be mentioned before the command to ensure redirection.
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Julieta
11 months ago
I disagree, I believe the answer is B. The sed command did not match anything in the file.
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Lewis
11 months ago
Whoa, talk about a classic shell command conundrum! I bet the folks who write these certification exams just love tripping us up with little gotchas like this.
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Janet
11 months ago
C) When the shell establishes the redirection it overwrites the target file before the redirected command starts and opens it for reading.
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Eliz
11 months ago
B) The command sed did not match anything in that file therefore the output is empty.
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Josefa
11 months ago
A) The file order is incorrect. The destination file must be mentioned before the command to ensure redirection.
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Alesia
12 months ago
I think the answer is C. The shell overwrites the target file before the command starts.
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