Windows console

Question

I would like to set the date in a Windows batch file to 7 days ago from today. I would like to do this in the following format.

Answer 1

A simpler option is to call a PowerShell command from within your batch script to manipulate the date. The batch script can set the date as 7 days in the past with a single line.

powershell -command "((Get-date).AddDays(-7)).ToString('yyyy-MM-dd')">captureVar && set /p Today=

The line starts out by instructing the cmd line to use PowerShell for the commands contained within the double quotes.

powershell -command "the powershell command(s)"

Next it used the PowerShell cmdlet Get-Date , and uses AddDays to change the date from the current value. A negative number will subtract and a positive number will add. The default format looks like

Friday, December 20, 2019 6:18:29 PM

To change the format you must change the date into a string with format instructions

.ToString('ffffdd MM/dd/yyyy HH:mm:ss.ffff K')

The output of the PowerShell command is redirected into a file named captureVar. Another option would have been to have PowerShell write it to a file.

powershell -command "((Get-date).AddDays(-7)).ToString('yyyy-MM-dd') | set-content 'captureVar'" && set /p Today=

I used && to make it a one liner. But you can set the var anytime after value has been written to the file.

set /p Today=

You should write in whatever scripting language you are most comfortable in. But remember that your options when writing a batch script isn't just batch commands. Windows has made it very easy to invoke PowerShell commands at anytime within your batch script. You can often find easy solutions to a given obstacle with PowerShell, insert that command into your script, then carry on as usual to finish your batch script.

A couple of things to remember when invoking PowerShell into your batch script:

Batch sees everything in double quotes as the PowerShell command. If you find a solution written in PowerShell that uses double quotes in the command, you must substitute those with single quotes. To escape characters, follow batch scripting rules. Batch variables can be read in the PowerShell command in the same way as batch (%var%). But values created in PowerShell must be redirected to be used later in your batch script. Any $var created in the PowerShell command is lost once the closing quote closes the PowerShell session.