What is the use of symbols under CMD/DOS

This article mainly introduces the use of symbols under CMD/DOS, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

_

I. single symbol

~

① means to use enhanced variable extensions in for.

② represents a string that specifies a location using an extended environment variable in% var:~n,m%.

③ represents a unary operator in set/an and inverts the operands bitwise.

!

① unary operators in set / a denote logically non. For example, set / a has zero, where a stands for logic 1.

@

① hides the echo of the command line itself and is often used in batches.

$

① indicates the end of a line in the findstr command.

In the prompt command, ② means to escape (symbolize or effect) subsequent characters.

%

The binary operator of ① in set / a, indicating the arithmetic remainder.

In the ② command line environment, the for command in is preceded by a character (which can be a letter, a number, or some specific character) to indicate that a loop or traversal metric variable is specified.

In a ③ batch, a number followed by a number refers to the specified parameter at the time of the current execution of the batch.

In other cases of ④,% will be removed (batch) or retained (command line)

^

① cancels the escape of specific characters, such as & | >

< ! "等，但不包括%。比如要在屏幕显示一些特殊的字符，比如>

> > | when ^ & and other symbols, you can add a ^ symbol before it to display the characters after the ^. ^ ^ is to display a ^, ^ | is to display a | character.

The binary operator of ② in set/a that represents bitwise XOR.

③ indicates in [] of findstr/r that it does not match the specified character set.

&

① command concatenation characters. For example, if I want to execute two commands at the same time on a line of text, I can connect the two commands with the & command.

② in set/an is bitwise and.

*

① stands for any character, which is what we usually call a "wildcard"; for example, if you want to find all the text files (.txt) in the root directory of disk c, you can type the command "dir c:\ * .txt".

The binary operator of ② in set / a, representing arithmetic multiplication.

③ in findstr/r means that the previous character will be matched multiple times.

-

① range representations, such as date lookups, can be used in the tokens operation in the for command.

② concatenates two characters in findstr/r to indicate a matching range.

③-A switch that follows the / of some commands to indicate the reverse.

④ in set / a:

1. Represents a negative number.

two。 Represents arithmetic subtraction.

+

① is mainly used in the copy command, which means that the + character is about to be used when many files are merged into one file.

The binary operator of ② in set/a, representing arithmetic addition.

:

The ① tag locator, which indicates that the following string is labeled and can be used as the object of the goto command. For example, a ": begin" tag is defined in the batch file. With the "goto begin" command, you can go to the ": begin" tag to execute the batch command.

② separates the variable name from the replaced string relationship in% var:string1=string2%.

| |

The ① pipe character is to use the output of the previous command as the input of the next command. "dir / a more b | more" can display the output information of the dir command screen by screen.

The binary operator of ② in set/a, representing bitwise or.

③ indicates in the help documentation that its front and back switches, options, or parameters are one of the two.

/

① indicates that the following character (string) is the function switch (option) of the command. For example, "dir / s/b/a-d" represents the different parameters specified by the "dir" command.

② represents division in set/a.

>

The ① command redirects the output of the command before it to the device behind it, and the contents of the device behind it are overwritten. For example, you can use "dir > lxmxn.txt" to output the result of the "dir" command to the "lxmxn.txt" text file.

② represents the right boundary of a matching word in findstr/r and needs to be used with the escape character\.

< ① 将其后面的文件的内容作为其前面命令的输入。 ② 在findstr/r中表示匹配单词的左边界，需要配合转义字符\使用。 = ① 赋值符号，用于变量的赋值。比如"set a=windows"的意思意思是将"windows"这个字符串赋给变量"a"。 ② 在set/a中表示算术运算，比如"set /a x=5-6*5"。 \ ① 这个"\"符号在有的情况下，代表的是当前路径的根目录.比如当前目录在c:\windows\system32下，那么你"dir \"的话，就相当与"dir c:\"。 ② 在findstr/r中表示正则转义字符。 , ① 在set /a中表示连续表达式的分割符。 ② 在某些命令中分割元素。 . ① 在路径的\后紧跟或者单独出现时： 一个.表示当前目录。 两个.表示上一级目录。 ② 在路径中的文件名中出现时： 最后的一个.表示主文件名与扩展文件名的分隔。 ? ① 在findstr/r中表示在此位置匹配一个任意字符。 ② 在路径中表示在此位置通配任意一个字符。 ③ 紧跟在/后表示获取命令的帮助文档。 __________________________________________________________________________________________ 　　　　　　　　　　　　二、多符号(符号不能分隔) && ① 连接两个命令，当&&前的命令成功时，才执行&&后的命令。 || ① 连接两个命令，当||前的命令失败时，才执行||后的命令。 >

&

① writes the output of one handle to the input of another handle.

>

The ① command redirector appends the output of the command before it to the device behind it.

The binary operator of ② in set / a, indicating that the logic shifts to the right.

= =

① determines whether the elements on both sides of = = are the same in the if command.

① represents the end of a word in the general expression of findstr.

_

3. Double symbol pairs (string must be specified between two symbols)

!!

① use! when variable delay is enabled! Expand the variable name to represent a reference to the variable value.

''

① in for/f means to execute what they contain as a command line and analyze their output.

② in for/f "usebackq" means to parse the strings they contain as strings.

(.)

① commands contain or have priority delimiters, such as the for command to use this (), we can also see it in commands such as if,echo.

② represents expression grouping in set / a.

"

The ① delimiter, which often uses "" to enclose a path when representing a path with spaces, is also required in some commands.

② parses what represents what they contain as a string in for/f.

③ in for/f "usebackq" indicates that the content they contain is treated as a file path and analyzes the contents of their files.

In other cases, ④ indicates that the content is a complete string, in which >,