What will be the output of grep -E '^[0-9]{3}-[a-z]{2}' data.txt if data.txt contains:

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Linux CLI - Text Processing

What will be the output of grep -E '^[0-9]{3}-[a-z]{2}' data.txt if data.txt contains:

123-ab line1
456-cd line2
78-ef line3
1234-gh line4

A78-ef line3

B123-ab line1 456-cd line2

C1234-gh line4

DNo output

Step-by-Step Solution

Solution:

Step 1: Understand the regex pattern
Pattern ^[0-9]{3}-[a-z]{2} matches lines starting with exactly 3 digits, a dash, then 2 lowercase letters.
Step 2: Check each line
Lines 1 and 2 start with 3 digits and 2 letters after dash; line 3 has only 2 digits; line 4 has 4 digits.
Final Answer:
123-ab line1 456-cd line2 -> Option B
Quick Check:
{n} means exact count in regex [OK]

Quick Trick: Use {n} to match exact n repetitions in grep -E [OK]

Common Mistakes:

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