Command line tool-grep

Grep Regular Expression metacharacters (basic set)

^ Start of the anchor row: '^ grep' matches all rows starting with grep.

$ The End Of The Anchor row is as follows: 'grep $ 'matches all rows ending with grep.

. Match a non-linefeed character such as: 'gr. P' match gr followed by any character, followed by P.

* Match zero or multiple previous characters, for example, '* grep'. Match All one or more spaces followed by the grep line. . * Represents any character.

[] Matches a character in a specified range, for example, '[Gg] rep' matches grep and grep.

[^] Match a character that is not within the specified range, for example, '[^ A-FH-Z] rep' match a line that does not start with a letter that does not contain the A-F and H-Z, followed by Rep.

\ (.. \) Indicates matching characters, such as '\ (love \)', and love is marked as 1.

\ <Specifies the start of a word, for example, '\ <grep' matches a row that contains a word starting with grep.

\> Anchor specifies the end of a word. For example, 'grep \> 'matches the row containing the word ending with grep.

X \ {M \} repeats the characters X and M consecutively. For example, 'O \ {5 \} 'matches the rows that contain 5 consecutive O Records.

X \ {M, \} repeats the character x continuously for at least m times, for example, 'O \ {5, \} 'matches rows with at least 5 o consecutively.

X \ {M, N \} repeats the character x consecutively, at least m times, no more than N times, for example, 'O \ {5, 10 \} 'matches rows of 5-10 consecutive O.

\ W matches a character with a number, that is, a [A-Za-z0-9], for example, 'g \ W * P' matches a character with g followed by zero or more characters or numbers, then p.

The inverse form of \ W. It matches a non-word character, such as a period ending. \ W * can match multiple.

The \ B word lock. For example, '\ bgrep \ B' only matches grep, that is, it can only be a grep word, with spaces on both sides.

Note: What are the metacharacters in the basic Regular Expression of grep ?, +, {, |, (,) Lose their special meanings and become common characters. To use special meanings, you can add the '\' prefix, or '-e' option (extended regular expression)

Grep "word1 \ | word2" test.txt

Grep-e "word1 | word2" test.txt

The preceding two commands are equivalent.

Common instances

1. Case Insensitive during search

grep -i "string" FILE

2. display the content of rows before and after matching rows

2.1. Show the N rows after matching rows

grep -A <N> "string" FILE

2.2. Show n rows before matching rows

grep -B <N> "string" FILE

2.3. Show n rows before and after matching rows

grep -C <N> "string" FILE

3. Match the entire word rather than the substring

grep -w "word" FILE

4. Use 'grep _ options' to highlight the matched string

export GREP_OPTIONS=‘--color=auto‘ GREP_COLOR=‘100;8‘

5. Reverse match

grep -v "string" FILE

6. Display rows that do not contain all specified strings

grep -v -e "pattren1" -e "pattren2" FILE

7. count the number of matched rows

grep -c "string" FILE

8. Display files containing matching items

grep -l "string" FILES

9. display only the rows that match the item, not the matched item.

grep -o "string" FILE

10. The row number is displayed in the output.

grep -n "string" FILE

11. Select the row containing six, seven, or eight.

grep -E "six|seven|eight" test.txt

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Command line tool-grep