Summary of common grep usage

Grep-elease 2. kernel 2.txt grep-Eh (ell | kernel displays grep-E ^ (h | y) tes not developed by h.

Grep-E l \ {2, \} 2.txt grep-E h (ell | a) o test.txt grep [a-z] \ {5, \} test.txt grep-xf a.txt B .txt // query the row grep-vxf B .txt a.txt that a and B exist together. // query that row a is not in file B, is the line grep-v ^ h test.txt that a has more than B. // displays grep-E ^ (h | y) tes not developed by h.

Grep-E 'l \ {2, \} '2.txt grep-E' h (ell | a) o 'test.txt grep '[a-z] \ {5, \} 'test.txt grep-xf a.txt B .txt // query the row grep-vxf B .txt a.txt that a and B exist together. // The row that queries a is not in file B, is the line grep-v '^ H' test.txt that a has more than B. // displays grep-E' ^ (h | y) not developed by h) 'test.txt //-E supports extended regular expressions, equivalent to egrep grep-A 1 'hello' test.txt // In addition to displaying matched rows, it also shows the grep-B 1 'hello' test.txt // In addition to displaying matched rows it also displays the previous line grep-C 1 'hello' test.txt // In addition to displaying the matched rows, It also displays the previous and subsequent lines grep-r "hello" Xx // search for grep-c in the xx directory // count the number of matched rows grep-n // display the row number grep-v '^ hello 'test.txt // display rows not starting with hello -- clever writing, the first digit is not developed by h, and the second digit is not developed by e... Grep '^ [^ h] \ | ^. [^ e] \ | ^ .. [^ l] \ | ^... [^ l] \ | ^ .... [^ o] '[options] Main Parameter:-c: only counts matching rows are output. -I: It is case-insensitive (only applicable to single characters ). -H: When querying multiple files, the file name is not displayed. -L: When querying multiple files, only names containing matching characters are output. -N: displays matching rows and row numbers. -S: the error message that does not exist or does not match the text is not displayed. -V: displays all rows that do not contain matched text. Command Regular Expression :. match a single character such .. X yiX can find out ^ match the beginning of A line ^ d the first character in each line is d $ match the end of A line T $ the last character in each line is T * match any string \ shield the meaning of special characters \ {2 \} B Letter A appears twice A \ {2, \} B appears at least twice A \ {2, 4 \} B appears 2 to 4 times [0-9] \ {4 \} xx [0-9] \ {4 \} the first four are numbers, in the middle is xx, and the last four are the main parameters of the number pattern Regular Expression: \: Ignore the original meaning of special characters in the regular expression. ^: Match the start line of the regular expression. $: Matches the end row of the regular expression. \ <: Starts from the row that matches the regular expression. Anchor specifies the start of a word, for example :/\
 
  
: Ends with the row matching the regular expression. []: A single character. For example, [A] indicates that A meets the requirements. [-]: Range, such as [A-Z], that is, A, B, C Until Z all meet the requirements ..: All single characters. *: There are characters. The length can be 0 [^] to match a character not in the specified range, for example: /[^ A-RT-Z] ed/match a line that starts with a letter that does not contain the A-R and T-Z, followed by ed. + Match the previous subexpression once or multiple times. For example, 'Zo + 'can match "zo" and "zoo", but cannot match "z ". + Is equivalent to {1 ,}.? Match the previous subexpression zero or once. For example, "do (es )? "Can match" do "in" do "or" does ".? It is equivalent to {0, 1 }. (? = Pattern) Forward pre-query: matches the search string at the beginning of any string that matches pattern. This is a non-get match, that is, the match does not need to be obtained for future use. For example, 'windows (? = 95 | 98 | NT | 2000) 'can match "Windows" in "Windows 2000", but cannot match "Windows" in "Windows 3.1 ". Pre-query does not consume characters, that is, after a match occurs, the next matching search starts immediately after the last match, instead of starting after the pre-query characters. (?! Pattern) Negative pre-query, match the search string at the start of any string that does not match Negative lookahead matches the search string at any point where a string not matching pattern. This is a non-get match, that is, the match does not need to be obtained for future use. For example, 'windows (?! 95 | 98 | NT | 2000) 'can match "Windows" in "Windows 3.1", but cannot match "Windows" in "Windows 2000 ". Pre-query does not consume characters, that is, after a match occurs, the next matching search starts immediately after the last match, instead of starting after the pre-query characters (?: Pattern) matches pattern but does not get the matching result. That is to say, this is a non-get match and is not stored for future use. This is useful when you use the "or" character (|) to combine each part of a pattern. For example, 'industr (?: Y | ies) is a simpler expression pcregrep 'Windows (? = 2000 | 95 | 98 | NT) 'test.txt // Windows is followed by 2000 or 95 .. pcregrep 'Windows (?! 2000 | 95 | 98 | NT) 'test.txt // pcregrep for Windows (?: 95 | 98 | NT | 2000) 'test.txt // same as the first type. egrep: an extended version of grep, which improves many operations that traditional grep cannot or are inconvenient. for example: Not Supported Under-grep? And + modifier, but egrep can. -grep does not support comparison between a, B, and (abc | xyz), but egrep does. fgrep: The expression is only used for string processing, and all meta functions are disabled. pcregrep: pcregrep-a grep with Perl-compatible regular expressions, perl regular expression, is the most popular and standard