Five. Regular expression grep, Egrep, Fgrep

Grep,egrep,fgrep:print lines matching a pattern

1.grep:

grep [options] PATTERN FILE ...

Pattern is made up of meta characters and ordinary characters

-I:--ignore-case, ignoring case

-O:--only-matching, displays only the characters that are matched, and two is not the whole line

-N:--line-number, outputs the line number of the matched row

-V:--invert-match, showing all rows except matching rows

-e:--extended-regexp, Egrep

-F:--fixed-strings, Fgrep

-P:--per-regexp

-A num:--after-context, which displays NUM lines after matching lines

-B Num:--before-context, display matching line strong NUM line

-C num:--context, displays the front and rear NUM lines of the matching line

Metacharacters

Match characters:

. : Matches any single character

[],[^]: matches the specified single character

[0-9], [[:d Igit:]]: matches a single number

[[: Alpha:]]: Matches a single large, lowercase letter

[[: Lower:]]: matches a single lowercase letter

[[: Upper:]]: Matches a single uppercase letter

[[: Alnum:]]: Matches a single number or letter

[[: Bank:]]: Matches a single white space character

[[:p UNCT:]]: Match punctuation

[[: Contrl:]]: match when control character

[[: Xdigit:]]: Matches a single 16 binary number

Number of matches: used to specify the number of occurrences of the preceding character

*: Any number of times, including 0

\+: At least once

\? : 0 or 1 times, the preceding characters can have, can be no

\{m\}, \{0,n\}, \{m,n\}, \{m,\}: Refers to M times, up to n times, m-n times, minimum m times

. *: Any length, any character

Location anchoring:

^: Anchor at the beginning of the line, mode left

$: End of line anchoring, mode right

\<: First anchor, Word pattern left, Word refers to a string of numbers and letters

\>: Ending anchor, Word right

^pattern$, matches the entire line only the specified pattern

^$: Blank Line

^[[:blank:]]$: No visible characters for entire line

\<word\>: Match Whole word

Group

\ (\) Enclose any character in parentheses to make a whole match.

Back reference: Apply the contents of the preceding grouping brackets, not the schema itself, \1,\2 ...

\ (th\). *\1: Matches what the first parenthesis matches

　　　　

2. Egrep: Equivalent to GREP-E

egrep [options] PATTERN FILE ...

Pattern is made up of meta characters and ordinary characters

-I:--ignore-case, ignoring case

-O:--only-matching, displays only the characters that are matched, and two is not the whole line

-N:--line-number, outputs the line number of the matched row

-V:--invert-match, showing all rows except matching rows

-A num:--after-context, which displays NUM lines after matching lines

-B Num:--before-context, display matching line strong NUM line

-C num:--context, displays the front and rear NUM lines of the matching line

Pattern is made up of meta characters and ordinary characters

Metacharacters

Match characters:

. : Matches any single character

[],[^]: matches the specified single character

[0-9], [[:d Igit:]]: matches a single number

[[: Alpha:]]: Matches a single large, lowercase letter

[[: Lower:]]: matches a single lowercase letter

[[: Upper:]]: Matches a single uppercase letter

[[: Alnum:]]: Matches a single number or letter

[[: Bank:]]: Matches a single white space character

[[:p UNCT:]]: Match punctuation

[[: Contrl:]]: match when control character

[[: Xdigit:]]: Matches a single 16 binary number

Number of matches: used to specify the number of occurrences of the preceding character

*: Any number of times, including 0

+: At least once

? : 0 or 1 times, the preceding characters can have, can be no

{m}, {0,n}, {m,n}, {m,}: Refers to M times, up to n times, m-n times, minimum m times

. *: Any length, any character

Location anchoring:

^: Anchor at the beginning of the line, mode left

$: End of line anchoring, mode right

\<: First anchor, Word pattern left, Word refers to a string of numbers and letters

\>: Ending anchor, Word right

^pattern$, matches the entire line only the specified pattern

^$: Blank Line

^[[:blank:]]$: No visible characters for entire line

\<word\>: Match Whole word

Group

() enclose any character in parentheses to make a whole match.

Back reference: Apply the contents of the preceding grouping brackets, not the schema itself, \1,\2 ...

(TH). *\1: Matches what the first parenthesis matches

3.fgrep: Regular expressions are not supported, matching only the specified string

Fgrep [optings] patern File ...

Five. Regular expression grep, Egrep, Fgrep