Linux Command learning: grep Text Search Tool

Mark: This series is just a record of the author in the Linux learning process of a bit, novice may refer to, the master will skip it!!!

Linux Learning Summary:grep Text Search Tool

function: According to the user-specified text pattern (search conditions) to the target file line by row search, and the matching line printed out, it's all called " Global Regular expression Print", globally regular expressions, which are open to all users by default.

syntax Format: Grep [option] Pattern file

Option: command options, specifically:

-V:--revert-match Reverse selection, showing all rows that do not contain matching files;

-I:--ignore-case ignores character case;

-C:--count calculates the number of columns that conform to the style

-E:--extended-regexp supports the use of regular expressions;

-A:--after-context in addition to displaying columns that conform to the template style and displaying the contents after that line

-B:--before-context In addition to displaying columns that conform to the template style and displaying the contents before the row

-C:--context In addition to displaying columns that conform to the template style and displaying the contents before the line

-N:--line-number The number of columns in the row before displaying the line that matches the style;

Example One showsall lines in the file "/tmp/testin.sh" that do not contain "Linux"

command: grep–v–n "Linux"/tmp/testin.sh

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example Two, query file "/tmp/testin.sh" keyword "Linux" case-insensitive all rows

Command: GREP-V-n "Linux"/tmp/testin.sh

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instance three, display contains the case " all lines of the Linux keyword and calculate the total

Command: Grep-v-n-c "Linux"/tmp/testin.sh

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Regular Expressions: Are patterns written by a class of characters, many of which do not represent their literal meaning, but rather express control or wildcard functions.

The regular expression meta-character, where:

Character Matching:

“.” : matches any single character, such as "GREP.P" matching grep followed by an arbitrary character;

"[]": matches any character within the specified range, such as "[Gg]rep" matches grep and grep;

"[^]": matches any character not in the specified range, such as "[^a-z]grep" matches the beginning of a letter that does not contain "A-Z" , followed by grep;

Location anchoring:

"^": beginning of line locator,"^grep" matches all lines starting with grep;

"$": End -of- line locator,"grep$" matches all lines ending with grep;

"^$": blank line;

"\<": anchors the beginning of a word, such as:"\<grep" matches a line containing a word that begins with "grep";

"\>": anchors the end of a word, such as:"grep\>" matches a line containing words ending with "grep";

Number of matches:

"*": matches 0 or more characters, such as "*grep" matches all one or more spaces followed by the line of grep;

". *": matches any character;

“\?” : 0 or one time, the preceding characters are optional, such as "Gr\?ep", the representative can be grep,EP;

"\{m\}": repeats M times, such as "grep\{2\}", matching rows containing at least 2 "grep" ;

"\{m,\}": repeat characters at least m times, such as "grep\{2,\}" matches at least 2 grep rows;

"\{m,n\}": repeat characters at least m times, up to n times, such as "grep\{2,3\}" matches 2 to 3 the line of grep;

POSIX characters:

[: Alnum:]: literal numeric characters;

[: Alpha:]: literal character;

[:d igit:]: numeric characters;

[: Graph:]: non-null characters (non-whitespace, control characters);

[: Lower:]: small characters;

[:p rint:]: non-null characters, including spaces;

[: Space:]: all whitespace characters (new lines, spaces, tabs);

[: Upper:]: Uppercase characters;

[:p UNCT:]: punctuation;

example Four, displayingthe word"grep", "grep" in the file " /tmp/test.grep"

command:grep–n "[Gg]rep"/tmp/test.grep

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example Five, displaytheline that begins with "grep" in the file "/tmp/test.grep"

command:cat/tmp/test.grep | grep ^grep

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example Six, displaysthe line in the file "/tmp/test.grep" that ends with"grep"

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example Seven, displays the line with at least one whitespace character in/tmp/test.grep;

command:grep-n "[[: space:]]\{1,\}$]/tmp/test.grep

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Cond!

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Linux Command learning: grep Text Search Tool