UNIX System administration: referencing

To complete this chapter, you can do the following things:

Use a referral mechanism on the command line to ignore the special meaning of special characters

8.1 Introducing References

Many characters have a "special" meaning in the shell:

-Space

-Carriage return

- $

- #

- *

-< >

References eliminate (ignore) the special meaning of these characters.

In Unix systems, some special characters have special meanings for the shell, for example, spaces are delimiters for commands and arguments; carriage returns send a signal to the shell to execute the command, and the $ symbol is used to display the value associated with the variable name.

In some special cases, you do not want the shell to heed the special meaning of these characters, you only ask to retain the literal meaning, so UNIX must provide a mechanism to ignore or eliminate the special meaning of the specified character, this mechanism is called a reference.

8.2 Reference Symbols

Backslash \

Single quote '

Double quote "

The backslash eliminates the special meaning of the special character immediately following it.

Single quotes (') eliminate the special meaning of special characters. The special meaning of all special characters enclosed in single quotes is ignored. The single quotation mark itself cannot be ignored because it is used to close the quoted string.

Double quotes (") are nearly as inclusive, double quotes can remove the special meaning of most special characters, only the $ symbol (when it is used as a variable and the command substitution), and the backslash exception. So you can use a backslash in double quotes to get rid of the special meaning of the $ number.

8.3 References--

Syntax：

\ Remove the special meaning of the next character

Example：

$ echo the \ \ Escapes the next character

The \ escapes the next character

$ color=red\ white\ and\ Blue

$ Ehco The http://www.aliyun.com/zixun/aggregation/9541.html ">value of \ $ colore is $color

The value of $colore is red white and blue

$ echo One nonblank \

>three Loko

One nonblank three Loko

The backslash ignores the special meaning of the following character, with no exceptions.