I'm trying to use variable in variable in conjunction with delayed expansion but still no luck.
SETLOCAL EnableDelayedExpansion
SET ERROR_COMMAND=exit /B ^!ERRORLEVEL^!
This is my last try. I want to setup an ERROR_COMMAND to be called when one of the steps in batch file crashes. The command is supposed to be:
IF ERRORLEVEL 1 !ERROR_COMMAND!
or
IF ERRORLEVEL 1 %ERROR_COMMAND%
The thing is, I'm not able to find out, how to SET properly the ERROR_COMMAND variable, so that ERRORLEVEL is not evaluated at the time of assignment, but at the time of evaluating the variable
Of course I can copy&paste the code all over the batch file, but using the variable just seems a bit prettier...
Anyone?
Thanks, Milan
I'm sure there are many ways to do this, here are two:
A)
SET ERROR_COMMAND=call echo.errlvl=%%ERRORLEVEL%%
verify failthis 2>nul
%ERROR_COMMAND%
B)
setlocal DISABLEDELAYEDEXPANSION&set "X=!"
call (endlocal&set "ERROR_COMMAND=echo.errlvl=%X%ERRORLEVEL%X%")&setlocal ENABLEDELAYEDEXPANSION
verify failthis 2>nul
%ERROR_COMMAND%
It should also be noted that if someone does set ERRORLEVEL=foo (In your script or "globally"), %ERRORLEVEL% will not resolve correctly (Same goes for %CD% and all the other built in special variables)
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Closed 2 years ago.
I'll boil my overall problem down to a very simple question. How do I assign a variable within a for loop within a batch file?
If I use the following batch file in windows:
for %%f in (.\Update\!dos\*.zip) do (
echo %%f
set FileName3=%%f
echo %FileName3%
pause
)
It will echo the proper value for %%f but it echoes nothing for %FileName3%
I then tested it by directly assigning FileName3 a direct value like test, which failed.
In searching for solutions, a common pointer is to use is SETLOCAL enabledelayedexpansion
However, if I add that to the top of my batch file, it simply stops running. So while I think this is likely part of the solution, without the ability to run the batch file to test, I can't determine.
To be clear, with SETLOCAL enabledelayedexpansion at the top of my batch file, if I double click the file nothing happens. If I run it from a command line, it just goes back to the prompt as though nothing happened.
So my question is, how can I assign a variable within a loop in a batch file? If the answer is to use SETLOCAL enabledelayedexpansion, then why is adding that to my batch file causing it to do absolutely nothing.
In your case, enabling delayed expansion at the top of your script will not work. The reason for that is that part of your source location includes the ! character, which due to delayed expansion will be omitted from the name, and your script will end because the path .\Update\dos\ does not exist.
The trick is to only enable delayed expansion, where you need it.
#Echo Off
SetLocal EnableExtensions DisableDelayedExpansion
If Not Exist "Update\!dos\*.zip" GoTo :EOF
For %%G In ("Update\!dos\*.zip") Do (
Echo %%G
Set "FileName3=%%G"
SetLocal EnableDelayedExpansion
Echo !FileName3!
EndLocal
)
Pause
What you need to be aware of however, is that any of your variables which are defined during the loops SetLocal will become undefined at the next EndLocal. This means if you need those variables later in the code, you'll need to use a method of passing those over the EndLocal barrier. That however is out of the scope of your specific code example, so has not been included in this example.
I'm trying to make a simple batch file ("javapath.bat") to add the Java compiler to the path when I need it so it won't be on the path all the time. I also want be able to do something like #call javapath.bat in other build scripts so the path can be added automatically when needed. Since those will be run repeatedly during the edit-save-compile-run grind, that means that javapath.bat needs to check if Java is already on the path and not readd it if it is, because apparently Microsoft thinks it's a good idea to let the path variable have lots of silly duplicates.
So to detect if it needs to be added I use setlocal to enable "command extensions" so I can use the environment variable string substitution thing. That ugliness works fine.
Then I use endlocal so I can actually set the enviroment variables without the changes being reverted at the end of the script. That's not working. Or, it certainly stops the variable changes being reverted, but it's not normal: it completely stops them from being visible locally, but they are still visible afterwards.
#echo off
setlocal enableextensions
if "%path:jdk1=%"=="%path%" (
endlocal
set ANT_HOME=C:\Program Files\Java\ant
set JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07
path %ANT_HOME%\bin;%path%
path %JAVA_HOME%\bin;%path%
)
After the above, ANT_HOME and JAVA_HOME are properly set. But the only change to PATH is that "\bin;" has been prepended to it, because none of the variables set during the script seem to be visible until afterwards (so ANT_HOME and JAVA_HOME are blank, and the first change to PATH is forgotten). Therefore, running it twice adds Java to the path okay, and not Ant. I could hardcode the paths twice but this behavior is so bizarre and ridiculous and I've been stuck on it for an hour.
Edit: Adding enabledelayedexpansion had no effect either.
#echo OFF
ECHO starting %PATH%
if "%path:jdk1=%"=="%path%" CALL :addjava
ECHO.
ECHO resulting %PATH%
GOTO :eof
:addjava
set ANT_HOME=C:\Program Files\Java\ant
set JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07
SET "path=%ANT_HOME%\bin;%JAVA_HOME%\bin;%path%"
GOTO :eof
This is what I'd use - other methods run afoul of the mininterpreted closing-parenthesis problem.
The key to understanding this odd behaviour is history. Batch has always substituted the parse-time value of any %var% into the code, then validated the result and executed if valid. As the language developed, it was necessary to maintain compatibility with existing batches, so you could only ADD new keywords and functionality, not remove or alter functionality.
So, as the capacity to call internal subroutines was added, and cascade instructions on a single line with '&' and allow multi-line instructions for if and for by enclosing the instructions in parentheses were introduced, and the capacity to use spaces and other separator characters in file or directory names was required, the batch language began to have a few little quirks.
It was a really bizarre decision to have the ! to access the run-time value of a variable invoked as a subclause of setlocal - personally, I'd have used a switch like ECHO on/off (ie EXPANSION on/off) but I'm not running the project. In the same way, DATE could have been equipped with a /u switch to return the date in a universal form, but the opportunity was missed (and continues to be missed, 17 years after NT4 and 5 wingenerations later...)
As others have noted, extensions should already be enabled except under rather extraordinary circumstances. All you need is to eliminate your SETLOCAL and restructure your IF a bit so that it exits the script if the PATH is already set.
#echo off
if not "%path:jdk1=%"=="%path%" exit /b
set "ANT_HOME=C:\Program Files\Java\ant"
set "JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07"
path %ANT_HOME%\bin;%path%
path %JAVA_HOME%\bin;%path%
If you really need to enable extensions, then
#echo off
setlocal enableExtensions
if not "%path:jdk1=%"=="%path%" exit /b
endlocal
set "ANT_HOME=C:\Program Files\Java\ant"
set "JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07"
path %ANT_HOME%\bin;%path%
path %JAVA_HOME%\bin;%path%
If your script has additional work to do, then
#echo off
setlocal enableExtensions
if not "%path:jdk1=%"=="%path%" goto :skip
endlocal
set "ANT_HOME=C:\Program Files\Java\ant"
set "JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07"
path %ANT_HOME%\bin;%path%
path %JAVA_HOME%\bin;%path%
:skip
REM carry on with additional code as needed
Everything inside the if block is evaluated in one go. So %ANT_HOME% has no effect after set ANT_HOME, you want delayed expansion you need to type:
setlocal enabledelayedexpansion
if "%path:jdk1=%"=="%path%" (
set ANT_HOME=C:\Program Files\Java\ant
set JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07
path = !ANT_HOME!;!path!
path = !JAVA_HOME!;!path!
)
:: important trick since they evaluate together %path% is still
:: what is inside local
endlocal & path %path%
path
Otherwise no delayed expansion. Also you need to use on undeleyed call with endlocal to escape the block. remember % variables never delay.
#echo off
cd %~dp0
md .\newfolder
for /f "usebackq delims=" %%f in ("list.txt") do (
call set /a add=%%add%%+1
call set addx=0000%%add%%
call set addx=%%addx:~-3%%
call copy "%%f" ".\newfolder\%%addx%%_%%f"
)
pause
I made simple namechange code. I usually use command without 'call' but here it makes error message . why is that? .. and when i use %variable% not %%variable%% , It doesn't work well..
plz tell me why it happens.. and last question.. environment variable's value is stored until exit cmd . I want to know how i can unset that.. thank you..
All code within a parenthesized block is parsed in one pass. Normal variable expansion using percents occurs at parse time. So if you set a variable within a block, you cannot access the value using normal expansion because the value will be the value that existed before you entered the block.
You have the above situation. There are two classic ways to resolve the problem.
1) You can use CALL and double the percents as you have done. The CALL solves the problem because normal expansion occurs twice for a called line - once for the entire block, and again before the line is executed, but after previous lines in the block have executed. The first expansion converts the double percents to single percents, and the second expansion actually expands the variable.
I do not like this solution because it is slow, and also because the CALL causes problems with quoted ^ characters - they are doubled.
You can use multiple CALLs on the same command. Each Call requires the percents to be doubled. So one CALL requires 2 percents, two CALLs requires 4 perecents, three CALLs 8 percents, etc.
2) I think the preferred solution is to use delayed expansion. It is much faster, and also you never have to worry about escaping or quoting special characters like &, |, >, < etc. when you used delayed expansion. Delayed expansion does just what it says - the variable is not expanded until just before the line is executed. Delayed expansion must be enabled before it can be used. Within a batch file you can use setlocal enableDelayedExpansion.
The one problem that can occur with delayed expansion is FOR variables are corrupted if they contain ! and delayed expansion is enabled when they are expanded. That can usually be solved by toggling delayed expansion on and off within the loop.
If you type HELP SET from the command prompt, you will get a pretty good description of the problem with expanding variables within a block of code, and how delayed expansion can help. The description starts about half way down with the words Finally, support for delayed environment variable expansion....
Note - you do not need to expand variables when used within a SET /A computation. SET /A will automatically expand the value at execution time. Undefined variables are treated as zero.
In your code, you can simply use set /a add=add+1
But there is an even simpler shorthand way - you can use the += operator: set /a add+=1.
Here is another way your code could be written without using CALL. The code is untested, but I think I got it right.
#echo off
setlocal disableDelayedExpansion
cd "%~dp0"
md newfolder
set add=0
for /f "usebackq eol=: delims=" %%F in ("list.txt") do (
set /a add+=1
set "file=%%F"
setlocal enableDelayedExpansion
set "addx=00!add!"
copy "!file!" "newfolder\!addx:~-3!_!file!"
endlocal
)
pause
I explicitly initialize add to 0 because it might already be set to a value. If you know that it is undefined or already set to 0, then the initialization is not needed.
Your FOR loop is dealing with file names, and ! is valid within file names. That is the reason I toggle delayed expansion on and off within the loop - I don't want file names with ! to be corrupted when I expand %%F. File names can also start with ; (though highly unlikely). If it does, then FOR will skip that file because the default EOL character is ;. A file can never start with :, so I like to set EOL to : instead.
I put SETLOCAL near the top so that the environment variable definitions do not persist after the batch file completes.
I notice in most scripts, the two are usually in the same line as so:
SETLOCAL ENABLEDELAYEDEXPANSION
Are the two in fact separate commands and can be written on separate lines?
Will setting ENABLEDELAYEDEXPANSION have an adverse effect on a script if it is set on the first lines of the script and not disabled until the end of the script?
I think you should understand what delayed expansion is. The existing answers don't explain it (sufficiently) IMHO.
Typing SET /? explains the thing reasonably well:
Delayed environment variable expansion is useful for getting around
the limitations of the current expansion which happens when a line of
text is read, not when it is executed. The following example
demonstrates the problem with immediate variable expansion:
set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "%VAR%" == "after" #echo If you see this, it worked
)
would never display the message, since the %VAR% in BOTH IF statements
is substituted when the first IF statement is read, since it logically
includes the body of the IF, which is a compound statement. So the IF
inside the compound statement is really comparing "before" with
"after" which will never be equal. Similarly, the following example
will not work as expected:
set LIST=
for %i in (*) do set LIST=%LIST% %i
echo %LIST%
in that it will NOT build up a list of files in the current directory,
but instead will just set the LIST variable to the last file found.
Again, this is because the %LIST% is expanded just once when the FOR
statement is read, and at that time the LIST variable is empty. So the
actual FOR loop we are executing is:
for %i in (*) do set LIST= %i
which just keeps setting LIST to the last file found.
Delayed environment variable expansion allows you to use a different
character (the exclamation mark) to expand environment variables at
execution time. If delayed variable expansion is enabled, the above
examples could be written as follows to work as intended:
set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "!VAR!" == "after" #echo If you see this, it worked
)
set LIST=
for %i in (*) do set LIST=!LIST! %i
echo %LIST%
Another example is this batch file:
#echo off
setlocal enabledelayedexpansion
set b=z1
for %%a in (x1 y1) do (
set b=%%a
echo !b:1=2!
)
This prints x2 and y2: every 1 gets replaced by a 2.
Without setlocal enabledelayedexpansion, exclamation marks are just that, so it will echo !b:1=2! twice.
Because normal environment variables are expanded when a (block) statement is read, expanding %b:1=2% uses the value b has before the loop: z2 (but y2 when not set).
ENABLEDELAYEDEXPANSION is a parameter passed to the SETLOCAL command (look at setlocal /?)
Its effect lives for the duration of the script, or an ENDLOCAL:
When the end of a batch script is reached, an implied ENDLOCAL is
executed for any outstanding SETLOCAL commands issued by that batch
script.
In particular, this means that if you use SETLOCAL ENABLEDELAYEDEXPANSION in a script, any environment variable changes are lost at the end of it unless you take special measures.
The ENABLEDELAYEDEXPANSION part is REQUIRED in certain programs that use delayed expansion, that is, that takes the value of variables that were modified inside IF or FOR commands by enclosing their names in exclamation-marks.
If you enable this expansion in a script that does not require it, the script behaves different only if it contains names enclosed in exclamation-marks !LIKE! !THESE!. Usually the name is just erased, but if a variable with the same name exist by chance, then the result is unpredictable and depends on the value of such variable and the place where it appears.
The SETLOCAL part is REQUIRED in just a few specialized (recursive) programs, but is commonly used when you want to be sure to not modify any existent variable with the same name by chance or if you want to automatically delete all the variables used in your program. However, because there is not a separate command to enable the delayed expansion, programs that require this must also include the SETLOCAL part.
A real problem often exists because any variables set inside will not be exported when that batch file finishes. So its not possible to export, which caused us issues. As a result, I just set the registry to ALWAYS used delayed expansion (I don't know why it's not the default, could be speed or legacy compatibility issue.)
In my pursuit of a solution to another environment-variable/batch-file related problem, I have once again come across a problem I have visited before (but cannot for the life of me remember how, or even if I solved it).
Say you have two BAT files (or one batch file and the command line). How can one pass an environment variable name to the other so that it can read the variable? The following example does not work:
A.BAT:
#call b.bat path
B.BAT:
#echo %%1%
> A.BAT
> %1
> B.BAT path
> %1
It is easy enough to pass the environment variable name, but the callee cannot seem to use it. (I don’t remember if or how I dealt with this the last time it came up, but I suspect it required the less-than-ideal use of redirecting temporary BAT files and calling them and such.)
Any ideas? Thanks.
You can use a little trick which unfortunately is nowhere documented:
call echo %%%1%%
Then you can use delayed expansion:
setlocal enabledelayedexpansion
echo !%1!
Delayed expansion helps here mostly because it uses other delimiters for the variable and evaluates them directly prior to running the command, while normally the evaluation might clash with normal parameter expansion.
Another way of overdoing this would be a subroutine:
call :meh "echo %%%1%%"
...
:meh
%~1
goto :eof
All examples, including the other answer, have one thing in common here: They all force cmd to evaluate variables/parameters twice. It won't work otherwise, since the first evaluation must produce %VariableName%, while the second will expand that to the variable's contents.
You can find the code also on my SVN.
B.BAT:
FOR /F "delims=" %%a IN ('echo.%%%1%%') DO set inputvar=%%a
echo %inputvar%
That is one way of doing it.
If all you want to do is echo it, you can do: echo.%%%1%%|more or echo %%%1%%|find /v ""