Assign output of a program to a variable using a MS batch file
https://stackoverflow.com/questions/2323292
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22-09-2019 - |
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I need to assign the output of a program to a variable using a MS batch file.
So in GNU Bash shell I would use VAR=$(application arg0 arg1). I need a similar behavior in Windows using a batch file.
Something like set VAR=application arg0 arg1.
Solution
One way is:
application arg0 arg1 > temp.txt
set /p VAR=<temp.txt
Another is:
for /f %%i in ('application arg0 arg1') do set VAR=%%i
Note that the first % in %%i is used to escape the % after it and is needed when using the above code in a batch file rather than on the command line. Imagine, your test.bat has something like:
for /f %%i in ('c:\cygwin64\bin\date.exe +"%%Y%%m%%d%%H%%M%%S"') do set datetime=%%i
echo %datetime%
OTHER TIPS
As an addition to this previous answer, pipes can be used inside a for statement, escaped by a caret symbol:
for /f "tokens=*" %%i in ('tasklist ^| grep "explorer"') do set VAR=%%i
@OP, you can use for loops to capture the return status of your program, if it outputs something other than numbers
assuming that your application's output is a numeric return code, you can do the following
application arg0 arg1
set VAR=%errorlevel%
On Executing: for /f %%i in ('application arg0 arg1') do set VAR=%%i i was getting error: %%i was unexpected at this time.
As a fix, i had to execute above as for /f %i in ('application arg0 arg1') do set VAR=%i
In addition to the answer, you can't directly use output redirection operators in the set part of for loop (e.g. if you wanna hide stderror output from a user and provide a nicer error message). Instead, you have to escape them with a caret character (^):
for /f %%O in ('some-erroring-command 2^> nul') do (echo %%O)
Reference: Redirect output of command in for loop of batch script
You could use a batch macro for simple capturing of command outputs, a bit like the behaviour of the bash shell.
The usage of the macro is simple and looks like
%$set% VAR=application arg1 arg2
And it works even with pipes
%$set% allDrives="wmic logicaldisk get name /value | findstr "Name""
The macro uses the variable like an array and stores each line in a seperate index.
In the sample of %$set% allDrives="wmic logicaldisk there will the following variables created:
allDrives.Len=5
allDrives.Max=4
allDrives[0]=Name=C:
allDrives[1]=Name=D:
allDrives[2]=Name=F:
allDrives[3]=Name=G:
allDrives[4]=Name=Z:
allDrives=<contains the complete text with line feeds>
To use it, it's not important to understand how the macro itself works.
The full example
@echo off
setlocal
call :initMacro
%$set% ipOutput="ipconfig"
call :ShowVariable ipOutput
echo First line is %ipOutput[0]%
echo(
%$set% driveNames="wmic logicaldisk get name /value | findstr "Name""
call :ShowVariable driveNames
exit /b
:ShowVariable
setlocal EnableDelayedExpansion
for /L %%n in (0 1 !%~1.max!) do (
echo %%n: !%~1[%%n]!
)
echo(
exit /b
:initMacro
if "!!"=="" (
echo ERROR: Delayed Expansion must be disabled while defining macros
(goto) 2>nul
(goto) 2>nul
)
(set LF=^
%=empty=%
)
(set \n=^^^
%=empty=%
)
set $set=FOR /L %%N in (1 1 2) dO IF %%N==2 ( %\n%
setlocal EnableDelayedExpansion %\n%
for /f "tokens=1,* delims== " %%1 in ("!argv!") do ( %\n%
endlocal %\n%
endlocal %\n%
set "%%~1.Len=0" %\n%
set "%%~1=" %\n%
if "!!"=="" ( %\n%
%= Used if delayed expansion is enabled =% %\n%
setlocal DisableDelayedExpansion %\n%
for /F "delims=" %%O in ('"%%~2 | findstr /N ^^"') do ( %\n%
if "!!" NEQ "" ( %\n%
endlocal %\n%
) %\n%
setlocal DisableDelayedExpansion %\n%
set "line=%%O" %\n%
setlocal EnableDelayedExpansion %\n%
set pathExt=: %\n%
set path=; %\n%
set "line=!line:^=^^!" %\n%
set "line=!line:"=q"^""!" %\n%
call set "line=%%line:^!=q""^!%%" %\n%
set "line=!line:q""=^!" %\n%
set "line="!line:*:=!"" %\n%
for /F %%C in ("!%%~1.Len!") do ( %\n%
FOR /F "delims=" %%L in ("!line!") Do ( %\n%
endlocal %\n%
endlocal %\n%
set "%%~1[%%C]=%%~L" ! %\n%
if %%C == 0 ( %\n%
set "%%~1=%%~L" ! %\n%
) ELSE ( %\n%
set "%%~1=!%%~1!!LF!%%~L" ! %\n%
) %\n%
) %\n%
set /a %%~1.Len+=1 %\n%
) %\n%
) %\n%
) ELSE ( %\n%
%= Used if delayed expansion is disabled =% %\n%
for /F "delims=" %%O in ('"%%~2 | findstr /N ^^"') do ( %\n%
setlocal DisableDelayedExpansion %\n%
set "line=%%O" %\n%
setlocal EnableDelayedExpansion %\n%
set "line="!line:*:=!"" %\n%
for /F %%C in ("!%%~1.Len!") DO ( %\n%
FOR /F "delims=" %%L in ("!line!") DO ( %\n%
endlocal %\n%
endlocal %\n%
set "%%~1[%%C]=%%~L" %\n%
) %\n%
set /a %%~1.Len+=1 %\n%
) %\n%
) %\n%
) %\n%
set /a %%~1.Max=%%~1.Len-1 %\n%
) %\n%
) else setlocal DisableDelayedExpansion^&set argv=
goto :eof
@echo off
SETLOCAL ENABLEDELAYEDEXPANSION
REM Prefer backtick usage for command output reading:
REM ENABLEDELAYEDEXPANSION is required for actualized
REM outer variables within for's scope;
REM within for's scope, access to modified
REM outer variable is done via !...! syntax.
SET CHP=C:\Windows\System32\chcp.com
FOR /F "usebackq tokens=1,2,3" %%i IN (`%CHP%`) DO (
IF "%%i" == "Aktive" IF "%%j" == "Codepage:" (
SET SELCP=%%k
SET SELCP=!SELCP:~0,-1!
)
)
echo actual codepage [%SELCP%]
ENDLOCAL
I wrote the script that pings google.com every 5 seconds and logging results with current time. Here you can find output to variables "commandLineStr" (with indices)
@echo off
:LOOPSTART
echo %DATE:~0% %TIME:~0,8% >> Pingtest.log
SETLOCAL ENABLEDELAYEDEXPANSION
SET scriptCount=1
FOR /F "tokens=* USEBACKQ" %%F IN (`ping google.com -n 1`) DO (
SET commandLineStr!scriptCount!=%%F
SET /a scriptCount=!scriptCount!+1
)
@ECHO %commandLineStr1% >> PingTest.log
@ECHO %commandLineStr2% >> PingTest.log
ENDLOCAL
timeout 5 > nul
GOTO LOOPSTART
