grep

grep is a powerful command-line utility used for searching text patterns in files. Here are some common use cases for grep:

Finding Text in Files: Search for a specific word or pattern in one or multiple files. For example:

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grep "pattern" file.txt
Recursive Search: Search for a pattern recursively in all files under a directory and its subdirectories. For example:

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grep -r "pattern" directory/
Case Insensitive Search: Perform a case-insensitive search. For example:

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grep -i "pattern" file.txt
Counting Matches: Count the number of lines that match a pattern. For example:

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grep -c "pattern" file.txt
Display Matching Line Numbers: Display line numbers along with matching lines. For example:

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grep -n "pattern" file.txt
Matching Whole Words: Search for the pattern as a whole word. For example:

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grep -w "pattern" file.txt
Using Regular Expressions: Utilize regular expressions for more complex pattern matching. For example:

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grep "^[0-9]" file.txt
Inverting Match: Display lines that do not match the pattern. For example:

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grep -v "pattern" file.txt
Displaying Context: Show lines before and after the matched lines. For example:

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grep -A 2 -B 1 "pattern" file.txt
Using Multiple Patterns: Search for lines matching any one of multiple patterns. For example:

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grep -e "pattern1" -e "pattern2" file.txt
Using Extended Regular Expressions: Enable extended regular expressions for more complex pattern matching. For example:

mathematica
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grep -E "pattern1|pattern2" file.txt