Convert string to integer on Windows Batch

Question

I've been searching a lot about how to convert a string into a integer on windows batch but I just can't get how to do it.

I've written a batch that copies a file from a directory to another and name it after the current date. My code goes something like this:

set FILE=log %date:~6,4%-%date:~3,2%-%date:~0,2% copy C:\log.txt C:\"%FILE%".txt

I need to do the conversion to make FILE be one day previous. For example, if I run the script right now, I'll get a file named "log 2014-07-09", but I want it to be "log 2014-07-08".

I've tried with this few sentences but I get an error about the numeric value is not valid:

set DAY=%date:~0,2% :: this assignation give me no problems
set /A DAY = %DAY%-1 :: this is the one that makes my head breaks

I don't know where the error is because I barely know windows batch sentences. I've read about the SET command syntax at Help command and other sites (like this one) but I can't get where I'm failing. I know this may be very simple (on some programming languages a Parse sentence would be enough), but I'm a total novice on this batch script stuff, so any help will be much appreciated. :)

PowerShell would make all of this a whole lot simpler: "{0:yyyy-MM-dd}.txt" -f (get-date).AddDays(-1). — Bill_Stewart
– Bill_Stewart, Commented Jul 9, 2014 at 21:28
You copy command is wrong. 1/ Remove the quotes around %file%. 2/ %file% equate to log /07/- 1-Th so your copy command is copy C:\log.txt C:\"log /07/- 1-Th".txt. That does not look right. — Noodles
– Noodles, Commented Jul 9, 2014 at 23:29
Will this be executed the fist day of month? The previous day will fall in the previous month. — MC ND
– MC ND, Commented Jul 10, 2014 at 7:48

SachaDee · Accepted Answer · 2014-07-10 09:55:01Z

1

A way to resolve it :

@echo off 
set "$DateNew=%date:~0,2%"
set /a "$DateNew=%$DateNew:0=%-1"
if %$DateNew%==0 set "$DateNew=10"
set "$DateNew=0%$DateNew%"
set "FILE=log %date:~6,4%-%date:~3,2%-%$dateNew:~-2%"

copy C:\log.txt C:\"%FILE%.txt"

edited Jul 10, 2014 at 9:55

answered Jul 9, 2014 at 23:27

SachaDee

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2 Comments

MC ND Over a year ago

set /a $DateNew=%$DateNew:0=%-1 If today is 10, the final value is 0

SachaDee Over a year ago

Oops ! Corrected Thanks @MC ND

Stephan · Accepted Answer · 2014-07-10 11:34:39Z

0

subtract one and keep a leading zero:

set a=08
set /a a=11%a%-1001
set a=%a:~1%
echo %a%

of course, 01- 1 = 00...

answered Jul 10, 2014 at 11:34

Stephan

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Comments

Bill_Stewart · Accepted Answer · 2014-07-10 14:50:30Z

0

All of the cmd shell script (batch) string-number parsing pain can be avoided in PowerShell:

copy-item C:\log.txt ("C:\{0:yyyy-MM-dd}.txt" -f (get-date).AddDays(-1))

This also avoids the "last day of the month" problem. For example, the code

"{0:yyyy-MM-dd}" -f (get-date "8/1/2014").AddDays(-1)

outputs 2014-07-31.

answered Jul 10, 2014 at 14:50

Bill_Stewart

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Bill_Stewart · Accepted Answer · 2014-07-10 19:18:19Z

0

This is a robust way to get yesterday's date with a batch file:

:: get yesterdays date
@echo off
set day=-1
echo >"%temp%\%~n0.vbs" s=DateAdd("d",%day%,now) : d=weekday(s)
echo>>"%temp%\%~n0.vbs" WScript.Echo year(s)^& right(100+month(s),2)^& right(100+day(s),2)
for /f %%a in ('cscript /nologo "%temp%\%~n0.vbs"') do set "result=%%a"
del "%temp%\%~n0.vbs"
set "YYYY=%result:~0,4%"
set "MM=%result:~4,2%"
set "DD=%result:~6,2%"
set "data=%yyyy%-%mm%-%dd%"

echo Yesterday was "%data%"
pause

edited Jul 10, 2014 at 19:18

Bill_Stewart

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answered Jul 10, 2014 at 15:11

foxidrive

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8 Comments

Bill_Stewart Over a year ago

Clever idea (create temporary VBScript script file). I still think PowerShell is easier...

foxidrive Over a year ago

@Bill_Stewart I like the idea of Powershell Bill, but it's crippled because every user has to jump through hoops to be able to run a powershell script. if Microsoft had generated a prompt on running the first PS script to ask if they want to allow the script once, the script all the time, or allow all scripts in the future - then it would have been more useful. As it stands the basic users don't have the skills to enable Powershell scripts.

Bill_Stewart Over a year ago

It's not really too difficult. Open an elevated command window and enter the command Set-ExecutionPolicy RemoteSigned. If the local user doesn't have administrator privileges, he/she can enter Set-ExecutionPolicy RemoteSigned CurrentUser. The execution policy can also be set in a GPO.

foxidrive Over a year ago

@Bill_Stewart It's not hard if you know how to do it. :)

Bill_Stewart Over a year ago

Same as your VBScript workaround - easy if you know how. :) I would argue that PowerShell is a more valuable skill to learn from this point forward.

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