Powershell copy-item using variable source names

Question

I'm new to PowerShell and still trying to figure things out. I have a script that will successfully copy a file from one location to another:

Copy-Item \\ServerName01\FolderName\file_09022020_0030.txt 
    -Destination \\ServerName02\FolderName\file_copied.txt

How can I write the script to use a variable source file name? I want to use a variable to find today's date minus 7 days and grab the corresponding file.

EX:

Copy-Item \ServerName01\FolderName\file_[variable today minus 7]*.txt 
    -Destination \ServerName02\FolderName\file_copied.txt

The variable date should be in the MMDDYYYY format. The timestamp at the end of each file can be ignored so I'm guessing that's a wildcard (*)

A new file is posted each day but the file name follows a pattern:

file_09022020_0030.txt
file_09012020_0030.txt
file_08312020_0305.txt
...
file_08262020_0451.txt
file_08252020_0305.txt
file_08242020_0305.txt

Answer 1

# Get a string representing 7 days ago in the specified format
# and store it in variable $dt
$dt = (Get-Date).AddDays(-7).ToString('MMddyyyy')

# Use variable $dt in the source file path pattern.
Copy-Item -Path        \\ServerName01\FolderName\file_${dt}_*.txt `
          -Destination \\ServerName02\FolderName\file_copied.txt

Note the {...} around the variable name, dt , which is required to tell PowerShell where the variable name ends, given that _ is a valid character in a variable name.

That said, there's no strict need for an intermediate variable, so instead of ${dt} you could directly embed
$((Get-Date).AddDays(-7).ToString('MMddyyyy')) in the source path, via $() , the subexpression operator .

See also:

• Get-Date

• System.DateTime.ToString

• Using variable references and subexpressions in unquoted command arguments .