问题
I'm trying to echo a string stored in a variable but it seems to require a lot of escaping. I'm trying with the following code:
setlocal EnableDelayedExpansion
@echo off
set "grass=@##&!$^&%**(&)"
echo !grass!
I want to echo the variable grass verbatim so I see a @##&!$^&%**(&) in the output. What should be done? Thanks!
回答1:
echo !grass! will always echo the current value verbatim, without the need of any escaping. Your problem is, the value is not what you think it is! The problem is occurring when you are trying to SET the value.
The correct escape sequence to set your value is
set "grass=@##&^!$^^&%%**(&)"
And now for the explanation. The information you need is buried in How does the Windows Command Interpreter (CMD.EXE) parse scripts?. But it is a bit hard to follow.
You have two problems:
1) % must be escaped as %% for each time the line will be parsed. The presence or absence of quotes makes no difference. The delayed expansion state also makes no difference.
set pct=%
:: pct is undefined
set pct=%%
:: pct=%
call set pct=%%
:: pct is undefined because the line is parsed twice due to CALL
call set pct=%%%%
:: pct=%
2) A ! literal must be escaped as ^! whenever it is parsed by the delayed expansion phase of the parser. If a line contains ! anywhere within it during delayed expansion, then a ^ literal must be escaped as ^^. But the ^ must also be either quoted or escaped as ^^ for the special character phase of the parser. This can be further complicated by the fact that a CALL will double up any ^ characters. (Sorry, it is very difficult to describe the problem, and the parser is complicated!)
setlocal disableDelayedExpansion
set test=^^
:: test=^
set "test=^"
:: test=^
call set test=^^
:: test=^
:: 1st pass - ^^ becomes ^
:: CALL doubles ^, so we are back to ^^
:: 2nd pass - ^^ becomes ^
call set "test=^"
:: test=^^ because of CALL doubling. There is nothing that can prevent this.
set "test=^...!"
:: test=^...!
:: ! has no impact on ^ when delayed expansion is disabled
setlocal enableDelayedExpansion
set "test=^"
:: test=^
:: There is no ! on the line, so no need to escape the quoted ^.
set "test=^!"
:: test=!
set test=^^!
:: test=!
:: ! must be escaped, and then the unquoted escape must be escaped
set var=hello
set "test=!var! ^^ ^!"
:: test=hello ^ !
:: quoted ^ literal must be escaped because ! appears in line
set test=!var! ^^^^ ^^!
:: test=hello ^ !
:: The unquoted escape for the ^ literal must itself be escaped
:: The same is true for the ! literal
call set test=!var! ^^^^ ^^!
:: test=hello ^ !
:: Delayed expansion phase occurs in the 1st pass only
:: CALL doubling protects the unquoted ^ literal in the 2nd pass
call set "test=!var! ^^ ^!"
:: test=hello ^^ !
:: Again, there is no way to prevent the doubling of the quoted ^ literal
:: when it is passed through CALL
回答2:
As dbenham said, it's only the assignment.
You could use the escaping like dbenham showed, it's necessary as EnableDelayedExpansion is active while you set the value.
Therefore you need to escape the exclamation mark and the caret must be escaped as there is one exclamation mark in the line, quotes are useless in that situation.
But you could also set the value before you activate the EnableDelayedExpansion,
Then you didn't need the carets.
来源：https://stackoverflow.com/questions/9757480/echo-exact-string-in-windows-batch-file