How to set commands output as a variable in a batch file

Question

Is it possible to set a statement\'s output of a batch file to a variable, for example:

findstr testing > %VARIABLE%

echo %VARIABLE%

Answer 1

To read a file...

set /P Variable=<File.txt

To Write a file

@echo %DataToWrite%>File.txt

note; having spaces before the <> character causes a space to be added at the end of the variable, also

To add to a file,like a logger program, First make a file with a single enter key in it called e.txt

set /P Data=<log0.log
set /P Ekey=<e.txt
@echo %Data%%Ekey%%NewData%>log0.txt

your log will look like this

Entry1
Entry2 

and so on

Anyways a couple useful things

Answer 2

I most cases, creating a temporary file named after your variable name might be acceptable. (as you are probably using meaningful variables name...)

Here, my variable name is SSH_PAGEANT_AUTH_SOCK

dir /w "\\.\pipe\\"|find "pageant" > %temp%\SSH_PAGEANT_AUTH_SOCK && set /P SSH_PAGEANT_AUTH_SOCK=<%temp%\SSH_PAGEANT_AUTH_SOCK

Answer 3

If you don't want to output to a temp file and then read into a variable, this code stores result of command direct into a variable:

FOR /F %i IN ('findstr testing') DO set VARIABLE=%i
echo %VARIABLE%

If you want to enclose search string in double quotes:

FOR /F %i IN ('findstr "testing"') DO set VARIABLE=%i

If you want to store this code in a batch file, add an extra % symbol:

FOR /F %%i IN ('findstr "testing"') DO set VARIABLE=%%i

A useful example to count the number of files in a directory & store in a variable: (illustrates piping)

FOR /F %i IN ('dir /b /a-d "%cd%" ^| find /v /c "?"') DO set /a count=%i

Note the use of single quotes instead of double quotes " or grave accent ` in the command brackets. This is cleaner alternative to delims, tokens or usebackq in for loop.

Tested on Win 10 CMD.