Chapter 3 Regular Expressions for Shell Learning

Regular Expression

\ <The \>: exact match of the, excluding words containing

[^ B-d]: does not contain B ~ D

A \ {2 \}: A appears twice

A \ {2, 3 \}: A appears 2 ~ 3 times

A \ {2 ,\}: A appears at least twice

[: Upper:]: uppercase letters (when used, add a layer of [] to indicate matching Character Set combination)

[: Lower:]: lowercase letter

[: Digit:]: Number

[: Alnum:]: uppercase/lowercase letters and numbers

[: Space:]: space or tab key

[: Alpha:]: uppercase/lowercase letters

Wildcard

Note that the wildcard is different from the regular expression, although there are common symbols

Ls-L *. Sh

Matches the file ending with. Sh, and * Indicates 0 or multiple prefix characters in the regular expression.

Ls-l 0 ?. Sh

Match the file that starts with 0 and ends with a character, ending with. Sh, and? Represents 0 or 1 character in an extended regular expression.

[] And [^] are used in the same way as regular expressions.

Grep

Text Search Tools

Grep [Option] [mode] [file]

-C only outputs the number of matched Korean

-I case-insensitive

-L only list matching file names, not specific Matching lines

-N: Lists All matched rows and displays row numbers.

-S does not display error messages that do not exist or do not match the text

-R recursive search not only searches for the current working directory, but also subdirectories

-Q: no result is output. Exit indicates whether the search is successful.

-E supports extended regular expressions.

-F does not support regular expressions and matches strings according to their literal meanings.

-H: When querying multiple files, the file name is not displayed.

-B prints the offset of the matched line spacing header, in bytes. If combined with-o, it is the offset of the matching word from the header.

-W matches the entire word, that is, the metacharacters of the regular expression in the pattern are not interpreted as special meanings. For example, CER * Is CER *

-X matches the entire line, that is, if word * is matched, the line of words can be word *.

Note: If the mode has spaces, use quotation marks. The file name can use wildcards (note that it is not a regular expression).-At the beginning must also be added to \ for transfer (think-option)

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