2016-2-5 Linux Basic Learning 11

grep, Egrep, Fgrep

grep: Searches text according to pattern and displays lines of text that conform to the pattern
Pattern: Text Word wildcards regular the expression's meta-word combination and fly match condition

grep [Options] PATTERN [FILE ...]
-I is case insensitive
--color to match the criteria of the search character color
-V shows rows that are not matched by a pattern
-O displays only strings that are matched to the pattern, one row
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*: Characters of any length
?: any single character
[]: matches any single character within the specified range
[^]: matches any single character outside the specified range

:
metacharacters :
    : matches any single character

matches (greedy mode, partial match)
match characters :
    *  : Match any of its preceding characters
    .* : Any character of any length
     [] : matches any single character within the specified range
    [^]: matches any single character outside the specified range
        [[:space:]]: blank character
        [[:p UNCT:]]: punctuation
         [[:lower:]]: Small Letter
        [[:upper:]]: Uppercase letter
         [[:alpha:]]: Uppercase and lowercase
        [[:d igit:]]: number
        [[:alnum:]]: Numeric and uppercase letters
   

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\？ : matches the preceding character 0/1 times

\{m,n\}: Matches its preceding characters, at least m times, up to N times
\{1,\} at least once, up to No limit
\{0,3\} up to three times
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Location anchoring :
^ Character: Anchor the beginning of the line, any content after this character must appear at the beginning of the line
Character $: Anchor Line end, any content after this character must appear at the end of the row
^$: Blank Line

\< or \b: Anchor word, any character following it must appear as the first word
\> or \b: anchors the ending, any character in front of which must appear as the tail of the word
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Grouping \ (\):
\ (ab\) *:ab can occur 0 times/1 times

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Reverse Reference
\1: Refers to the first opening parenthesis and all the contents of the corresponding closing parenthesis
\2: Refers to the second opening parenthesis and all the contents of the corresponding closing parenthesis
\3: Refers to the third opening parenthesis and all the contents of the corresponding closing parenthesis

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This article is from the "11160930" blog, please be sure to keep this source http://11170930.blog.51cto.com/11160930/1741277

2016-2-5 Linux Basic Learning 11