Po delsi dobe jsem se k tomu zas dostal, stahl build 2500 a koukam ze zavorky
stale haluzi:
if "%%b"=="" (echo.) else ()
uvedena konstrukce zvyrazni bere v uvahu pouze prvni zavorku, zbytek ignoruje.
Obecne by se ve Windows scriptech mely zavorky ignorovat pouze pokud jsou uvnitr
dvojitych uvozovek (pak se povazuji za soucast stringu) nebo pokud jsou
escapnuty striskou ^( ^)
Vyborne tematicke cteni zde:
----------------------------------------------
The BatchLineParser:
A line of code in a batch file has multiple phases (on the command line the
expansion is different!).
The process starts with phase 1
Phase/order
1) Phase(Percent):
•A double %% is replaced by a single %
•Expansion of argument variables (%1, %2, etc.)
•Expansion of %var%, if var does not exists replace it with nothing
•For a complete explanation read this from dbenham Same thread: percent
expansion
1.5) Remove all <CR> (CarriageReturn 0x0d) from the line
2) Phase(Special chars, " <LF> ^ & | < > ( ): Look at each character
•If it is a quote (") toggle the quote flag, if the quote flag is active, the
following special characters are no longer special: ^ & | < > ( ).
•If it is a caret (^) the next character has no special meaning, the caret
itself is removed, if the caret is the last character of the line, the next line
is appended, the first charater of the next line is always handled as escaped
charater. •<LF> stops the parsing immediatly, but not with a caret in front
•If it is one of the special characters & | < > split the line at this point,
in case of the pipe (|) both parts gets a phase restart (a bit more complex ...)
For more info on how pipes are parsed and processed, look at this question and
answers: Why does delayed expansion fail when inside a piped block of code?
•In this phase the primary token list is build, token delimiters are <space>
<tab> , ; = and <0xFF> (also known as non-breaking space)
•Process parenthesis (provides for compound statements across multiple lines):
•If the parser is not looking for a command token, then ( is not special.
•If the parser is looking for a command token and finds (, then start a new
compound statement and increment the parenthesis counter
•If the parenthesis counter is > 0 then ) terminates the compound statement
and decrements the parenthesis counter.
•If the line end is reached and the parenthesis counter is > 0 then the next
line will be appended to the compound statement (starts again with phase 1)
•If the parenthesis counter is = 0, and the parser is looking for a commmand,
then ) and all remaining characters on line are ignored
•In this phase REM, IF and FOR are detected, for the special handling of
them.
•If the first token is "rem", only two tokens are processed, important for the
multiline caret
3) Phase(echo): If "echo is on" print the result of phase 1 and 2
•For-loop-blocks are echoed multiple times, first time in the context of the
for-loop, with unexpanded for-loop-vars
•For each iteration, the block is echoed with expanded for-loop-vars
---- These two phases are not really follows directly, but it makes no
difference
4) Phase(for-loop-vars expansion): Expansion of %%a and so on
5) Phase(Exclamation mark): Only if delayed expansion is on, look at each
character
•If it is a caret (^) the next character has no special meaning, the caret
itself is removed
•If it is an exclamation mark, search for the next exclamation mark (carets
are not observed anymore), expand to the content of the variable •Consecutive
opening ! are collapsed into a single !
•Any remaining ! that cannot be paired is removed
•If no exclamation mark is found in this phase, the result is discarded, the
result of phase 4 is used instead (important for the carets)
•Important: At this phase quotes and other specical characters are ignored
•Expanding vars at this stage is "safe", because special characters are not
detected anymore (even <CR> or <LF>)
6) Phase(call/caret doubling): Only if the cmd token is CALL
•If the first token is "call", start with phase 1 again, but stops after phase
2, delayed expansion are not processed a second time here
•Remove the first CALL, so multiple CALL's can be stacked
•Double all carets (the normal carets seems to be stay unchanged, because in
phase 2 they are reduced to one, but in quotes they are effectivly doubled)
7) Phase(Execute): The command is executed
•Different tokens are used here, depends on the internal command executed
•In case of a set "name=content", the complete content of the first equal sign
to the last quote of the line is used as content-token, if there is no quote
after the equal sign, the rest of the line is used.
Zdroj:
http://stackoverflow.com/questions/4094699/how-does-the-windows-command-interpre
ter-cmd-exe-parse-scripts
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