Set output of a command as a variable (with pipes)
I find myself a tad amazed at the lack of what I consider the best answer to this question anywhere on the internet. I struggled for many years to find the answer. Many answers online come close, but none really answer it. The real answer is
(cmd & echo.) >2 & (set /p =)<2
The "secret sauce" being the "closely guarded coveted secret" that "echo." sends a CR/LF (ENTER/new line/0x0D0A). Otherwise, what I am doing here is redirecting the output of the first command to the standard error stream. I then redirect the standard error stream into the standard input stream for the "set /p =" command.
Example:
(echo foo & echo.) >2 & (set /p bar=)<2
The lack of a Linux-like backtick/backquote facility is a major annoyance of the pre-PowerShell world. Using backquotes via for-loops is not at all cosy. So we need kinda of setvar myvar cmd-line
command.
In my %path%
I have a dir with a number of bins and batches to cope with those Win shortcomings.
One batch I wrote is:
:: setvar varname cmd
:: Set VARNAME to the output of CMD
:: Triple escape pipes, eg:
:: setvar x dir c:\ ^^^| sort
:: -----------------------------
@echo off
SETLOCAL
:: Get command from argument
for /F "tokens=1,*" %%a in ("%*") do set cmd=%%b
:: Get output and set var
for /F "usebackq delims=" %%a in (`%cmd%`) do (
ENDLOCAL
set %1=%%a
)
:: Show results
SETLOCAL EnableDelayedExpansion
echo %1=!%1!
So in your case, you would type:
> setvar text echo Hello
text=Hello
The script informs you of the results, which means you can:
> echo text var is now %text%
text var is now Hello
You can use whatever command:
> setvar text FIND "Jones" names.txt
What if the command you want to pipe to some variable contains itself a pipe?
Triple escape it, ^^^|
:
> setvar text dir c:\ ^^^| find "Win"
THIS DOESN'T USE PIPEs, but requires a single tempfile
I used this to put simplified timestamps into a lowtech daily maintenance batfile
We have already Short-formatted our System-Time to HHmm, (which is 2245 for 10:45PM)
I direct output of Maint-Routines to logfiles with a $DATE%@%TIME% timestamp;
. . . but %TIME% is a long ugly string (ex. 224513.56, for down to the hundredths of a sec)
SOLUTION OVERVIEW:
1. Use redirection (">") to send the command "TIME /T" everytime to OVERWRITE a temp-file in the %TEMP% DIRECTORY
2. Then use that tempfile as the input to set a new variable (I called it NOW)
3. Replace
echo $DATE%@%TIME% blah-blah-blah >> %logfile%with
echo $DATE%@%NOW% blah-blah-blah >> %logfile%
====DIFFERENCE IN OUTPUT:
BEFORE:
SUCCESSFUL TIMESYNCH [email protected]AFTER:
SUCCESSFUL TIMESYNCH 29Dec14@2252
ACTUAL CODE:
TIME /T > %TEMP%\DailyTemp.txt SET /p NOW=<%TEMP%\DailyTemp.txt echo $DATE%@%NOW% blah-blah-blah >> %logfile%
AFTERMATH:
All that remains afterwards is the appended logfile, and constantly overwritten tempfile. And if the Tempfile is ever deleted, it will be re-created as necessary.
Your way can't work for two reasons.
You need to use set /p text=
for setting the variable with user input.
The other problem is the pipe.
A pipe starts two asynchronous cmd.exe instances and after finishing the job both instances are closed.
That's the cause why it seems that the variables are not set, but a small example shows that they are set but the result is lost later.
set myVar=origin
echo Hello | (set /p myVar= & set myVar)
set myVar
Outputs
Hello
origin
Alternatives: You can use the FOR loop to get values into variables or also temp files.
for /f "delims=" %%A in ('echo hello') do set "var=%%A"
echo %var%
or
>output.tmp echo Hello
>>output.tmp echo world
<output.tmp (
set /p line1=
set /p line2=
)
echo %line1%
echo %line2%
Alternative with a macro:
You can use a batch macro, this is a bit like the bash equivalent
@echo off
REM *** Get version string
%$set% versionString="ver"
echo The version is %versionString[0]%
REM *** Get all drive letters
`%$set% driveLetters="wmic logicaldisk get name /value | findstr "Name""
call :ShowVariable driveLetters
The definition of the macro can be found at
SO:Assign output of a program to a variable using a MS batch file