[Solved] Why does the command sed 's/foo/bar/g' file.txt > file.txt often result in an empty file? — Ans: Because redirecting output to the same file truncates it before sed reads | Linux CLI

Linux CLI - Text Processing

Why does the command sed 's/foo/bar/g' file.txt > file.txt often result in an empty file?

ABecause sed deletes all lines containing 'foo'

BBecause redirecting output to the same file truncates it before sed reads

CBecause 'g' flag causes sed to remove lines

DBecause sed cannot write to files

Step-by-Step Solution

Solution:

Step 1: Understand shell redirection behavior
Redirecting output with '>' to the same file truncates the file immediately before sed reads it.
Step 2: Effect on sed command
Since the file is emptied before sed processes it, sed reads an empty file and writes nothing, resulting in an empty file.
Final Answer:
Because redirecting output to the same file truncates it before sed reads -> Option B
Quick Check:
Redirecting output to input file empties it before reading [OK]

Quick Trick: Avoid redirecting output to input file directly [OK]

Common Mistakes:

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