Special characters in the shell

Introduction [54,17]

Bash itself does not support regular expression regex, while some tools under the shell support the interpretation of Regex , and the use of regex is Shell commands and tools , such as Grep,sed,awk. but the shell supports wildcard characters , which are different from regex, and the wildcard is to store a non-specific file name extension that contains wildcards in the computer , The process of a batch of specific file names on a server or network .

Wildcard file name matching

Wildcards are used to match file names, path names, including commands, and typically combine four kinds of wildcard methods . a Linux file name can use any printable character except/out (the opening and closing of a file name is difficult to identify unless intentionally, avoid using spaces and tabs to name the file to avoid unnecessary hassles). Files that begin with a. File are hidden.

? * [] {} ^ and internal variable globignore make up all the contents of the shell wildcard.

*	Matches 0 or more characters (except for the beginning of the.), which can be matched to another location, which may be an empty string
?	Matches any single character except the first character (except for the beginning of the.) and does not match the null
[...]	Match any one of the characters in the list or range
[^...]	Match any one of the characters given in the list or out of range
{}	Represents a collection of a set of strings

Using the example

[ABCD] match any one of the ABCD characters

[A-h] 　 Any one of the characters in the a-h

[0-9] match any number in a 0-9

[A-za-z0-9]

[!0-9]

Mkdir/touch Test{a,b}

MKDIR/TOUCH/TEST/{A,B}

LS [xyz]*.conf

Shell Special Symbols

About referencing Quote

A reference is a string that is caused by a reference symbol to prevent special characters from being re-interpreted by the shell script to other meanings, and to screen special characters for special meanings , and to interpret them as literal meanings, which are used to refer to characters that have escape characters \, single quotes ' double quotes '

The shell only wants to treat the special characters it handles as ordinary characters. bash Shell has three ways to avoid characters being interpreted by the shell .

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Other special characters

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Special characters in the shell