For loops in Windows command lineDaniele Esposti's Blog, in 12 July 2013
I’m working on a script on Windows to automatically install Python packages listed in a text file like
easy_install doesn’t support a
requirements.txt as a packages’ list I made a small Batch file to simulate the
pip’s behavior, and I discovered the for loop of Windows’s command line.
The idea is to read the content of
requirements.txt and execute
easy_install for every line of the input file. The for loop has a multitude of options not to only iterate on a list of values, but also to iterate on the content of a file (or list of files) using a set of parsing keywords to extract tokens from every line.
The final script looks like this:
for /f "tokens=*" %%p in (requirements.txt) do ( easy_install %%p if %errorlevel% gtr 1 ( echo %errorlevel% exit /b 2 ) )
Really is looking different than any standard for loop you can find in any programming language but don’t forget the for loop is a real built-in command line application which needs arguments and command line’s options in order to work.