Beginner LevelLinux Commands & SysAdmin
How do you search files using grep, egrep, and fgrep with regular expressions?
❓ Interview Prompt: Explain grep, case-insensitive search (-i), recursive search (-r), line numbers (-n), invert match (-v), and regex patterns.
'grep' (Global Regular Expression Print) searches text files line-by-line for specified patterns:
Essential Flags:
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'-i': Case-insensitive matching.
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'-r' / '-R': Recursive directory search.
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'-n': Print line numbers alongside matching text.
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'-v': Invert match (select non-matching lines).
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'-E': Enable Extended Regular Expressions (formerly 'egrep').
Code Implementation Example
bash
# Search recursively for 'ERROR' (case-insensitive) showing line numbers
grep -rnI "error" /var/log/app/
# Exclude commented lines from configuration file
grep -v "^#" /etc/nginx/nginx.conf | grep -v "^$"💡Searching text and filtering config files using grep flags.
🎯 Interview Key Takeaway
Use grep -rni to recursively search text patterns in directories while ignoring binary files.
#grep#Text Search#Regex#Beginner
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