0520 Sixth session

Description and usage of special permissions go directly to the end of the note in the previous lesson

Text Processing Tools

1.cut: Cut the data into segments with a separator and extract one of the sections

-d:d followed by the delimiter directly

-f:f back with the number of segments you want to extract, multiple segments, separated

2.more/less: Page Turn display

COMMAND |more/less-d: D is a few simple help tips

3.head: Display the first few lines

-#: Show Front # line

4.tail: Show the end of a few lines

-#: Show End # line

-F: Monitoring end Add, usually with & background use

-N +k: Starting from line K

5.paste: Merge Command

-D: Delimiter, two files merged together to differentiate between two data separators

-S: one row of data

6.uniq: Count of commands

-C: Number of occurrences of statistics

-U: Show rows with no duplicates

-D: Show Duplicate rows

7.diff: Compare the differences between two files

-U: The structure of the comparison is output in a special format and can be used as a patch when redirected to a file

8.patch:

-I: Change the format of File1 to diff output to File2

-R: Converts the file2 to a diff output format into file1

-B: Back up and save a copy before doing IR operation

Regular expressions and Linux text Processing Three Musketeers

Text Processing Three musketeers: grep: Filtering text

Sed: Editing text

awk: Text Report Generator

grep: Filter Text Tool

grep: Supports regular expressions

Egrep: Supports extended expressions

Fgrep: Regular expressions are not supported

Between three can be converted by option: Grep-e =egrep

Grep-f =fgrep

grep "Options" pattern file

-I: Case sensitive

-O: No rows are displayed, only matching data is displayed

-V: Shows what is outside the row where the matched data is located

-Q: Silent mode, regardless of whether the match is not displayed

-E: Supports extended regular expressions

-A #:after, the next # line of the matched line is also displayed

-B #:before, up # line

-C #: Context, Upper and lower # lines

Regular expressions: Just some symbols for the text, and the previous * a bit similar, but the meaning of each symbol is completely different, pay attention not to confuse

Character matching:. : Any single character

[]: Specify any single character of the range

[^]: Create any single character outside the range

[: Space:] [:d Igit:] [: Alnum:] [: Alpha:] [: Lower:] [: Upper:] [:p UNCT:]

Meaning with wildcard characters

Word number match: *: The character of the front appears as many times as 0,1,2, ....

\?: The preceding character appears 0 or 1 times, i.e. the data in front is optional

\+: The preceding character appears more than 1 times

\{m\}: The characters in front appear m times, one less time, no more

\{m,n\}: The character at the front appears at most n times at least m times

\{0,n\}: Up to n occurrences of characters in front

\{m,\}: The character at the front appears at least m times

Position anchoring: ^: Beginning of line, on the left of pattern

$: Line bit right

^$: Blank lines, not even spaces

^[:space:]*$: Blank line, with spaces

\<: The head of the word, placed on the left side of the word

\>: Ending, right

\<\>: Word anchoring

Grouping and referencing: \ (\): Fu Guacheng multiple words into a whole

\1: Refers to the front parenthesis, from the leftmost first left parenthesis, to its matching parentheses, the contents of the parentheses inside

\2: two X

\3: three X

\4: Four X

Note: This type of reference is called a back reference

Egrep: Extended Regular expression content is basically the same as regular expressions, except that when the words match, the \ can not be added

Different

Or: |:| all content on the left or | right all content

Note: | When used in certain environments, add \ to escape

C|CD: Refers to C or CD instead of CD or CD, want to express the meaning of the latter need to use the grouping, that is, parentheses

\ (c|c\) d to indicate

Fgrep: grep that does not support regular expressions is not useless, because many of the documents we want to retrieve in the future are large documents with very large data, so in the case of non-regular expressions,

The efficiency of using fgrep will be higher

Regular expression is an important content, but also a need to move the brain content, should do more practice

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0520 Sixth session