Using a powershell variable in multiple commands within a Windows batch file

Question

In a Windows 7 batch file, I can call powershell v2 to create a string and then assign that string to a batch file variable to later use within another command, like this:

for /f "delims=" %%a in ('powershell -noninteractive -NoProfile -Command "Get-Date -format 'yyyy-MM-dd HH_mm_ss'"') do set "datetime=%%a"
rem process file1.txt here
ren file1.txt "newname %datetime%.txt"

If I try to do the same thing (within a batch file), in a simpler way, it doesn't work:

^{Editor's note: Turns out it does work - the inner " instances are correctly escaped as \".}

powershell -noninteractive -NoProfile -Command "$datetime_string = Get-Date -format 'yyyy-MM-dd HH_mm_ss'; (gc file1.txt) -join [char]10 | Out-File -Encoding Ascii \"newname $datetime_string.txt\""

Can you help?

@TessellatingHeckler Hmmm... stackoverflow.com/a/44637674/4182398 states otherwise, or am I misunderstanding it? — Amazon Dies In Darkness
– Amazon Dies In Darkness, Commented Jun 20, 2017 at 0:09
@RockPaperLizard: Re \": you're not misunderstanding: when PowerShell is invoked from the outside world (such as from a batch file), " chars. must indeed be escaped as \" - which is surprising and little-known, given that within PowerShell you must embed " chars. inside "..." as `" — mklement0
– mklement0, Commented Jun 20, 2017 at 1:29
@RockPaperLizard wow, it is. I thought ^ was the command prompt escape. Beg 'pardon. — TessellatingHeckler
– TessellatingHeckler, Commented Jun 20, 2017 at 2:26
@TessellatingHeckler: ^ only works when it is used unquoted. Inside a double-quoted string (from cmd's perspective), the only thing that cmd itself recognizes is "", which, however, is only recognized by MS-compiled programs and, with limitations, by batch files. For the whole sordid tale, see this answer of mine. — mklement0
– mklement0, Commented Jun 20, 2017 at 14:32

user6811411 · Accepted Answer · 2017-06-19 22:27:37Z

2

If the inner double quotes are a problem, you can simply avoid them:

powershell -NonI -NoP -Com  "$DT=Get-Date -format 'yyyy-MM-dd HH_mm_ss';(gc file1.txt) -join [char]10|Out-File ('newname '+$DT+'.txt') -Enc Ascii"

For brevity parameter and variable names are shortened as much as possible.

answered Jun 19, 2017 at 22:27

user6811411

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mklement0 Over a year ago

++ for a viable alternative, but it's worth noting that the OP's command actually does work, due to correctly escaping embedded " instances as \". That said, your approach is ultimately preferable, because it avoids the risk of cmd unexpectedly interpreting a part of the command line itself, due to not recognizing \" as an escaped double quote and actually considering it the end of a double-quoted string.

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