How do I strip part of a file name?

Question

Suppose I have a file database_partial.xml.

I am trying to strip the file from "_partial" as well as extension (xml) and then capitalize the name so that it becomes DATABASE.

Param($xmlfile)

$xml = Get-ChildItem "C:\Files" -Filter "$xmlfile"

$db = [IO.Path]::GetFileNameWithoutExtension($xml).ToUpper()

That returns DATABASE_PARTIAL, but I don't know how to strip the _PARTIAL part.

Replace could be used: $db = [io.path]::GetFileNameWithoutExtension($xml).ToUpper() -replace "_PARTIAL" — jfrmilner, Mar 13 '19 at 23:43
@jfrmilner shouldnt it be replace with something? like replace with "" — Cataster, Mar 13 '19 at 23:47
@jfrmilner single parameter? so you mean by default replace will remove the _partial and replace it with nothing right? — Cataster, Mar 13 '19 at 23:53

score 2 · Accepted Answer · edited Mar 14 '19 at 01:47

You don't need GetFileNameWithoutExtension() for removing the extension. The FileInfo objects returned by Get-ChildItem have a property BaseName that gives you the filename without extension. Uppercase that, then remove the "_PARTIAL" suffix. I would also recommend processing the output of Get-ChildItem in a loop, just in case it doesn't return exactly one result.

Get-ChildItem "C:\Files" -Filter "$xmlfile" | ForEach-Object {
    $_.BaseName.ToUpper().Replace('_PARTIAL', '')
}

If the substring after the underscore can vary, use a regular expression replacement instead of a string replacement, e.g. like this:

Get-ChildItem "C:\Files" -Filter "$xmlfile" | ForEach-Object {
    $_.BaseName.ToUpper() -replace '_[^_]*$'
}

mklement0 · Answer 2 · 2022-03-11T00:31:32.720

Ansgar Wiechers's helpful answer provides an effective solution.

To focus on the more general question of how to strip (remove) part of a file name (string):

Use PowerShell's -replace operator, whose syntax is:
<stringOrStrings> -replace <regex>, <replacement>:

<regex> is a regex (regular expression) that matches the part to replace,
<replacement> is replacement operand (the string to replace what the regex matched).
- In order to effectively remove what the regex matched, specify '' (the empty string) or simply omit the operand altogether - in either case, the matched part is effectively removed from the input string.

^{For more information about -replace, see this answer.}

Applied to your case:

$db = 'DATABASE_PARTIAL' # sample input value

PS> $db -replace '_PARTIAL$', ''  # removes suffix '_PARTIAL' from the end (^)
DATABASE

PS> $db -replace '_PARTIAL$'      # ditto, with '' implied as the replacement string.
DATABASE

Note:

-replace is case-insensitive by default, as are all PowerShell operators. To explicitly perform case-sensitive matching, use the -creplace variant.
By contrast, the [string] type's .Replace() method (e.g., $db.Replace('_PARTIAL', ''):
- matches by string literals only, and therefore offers less flexibility; in this case, you couldn't stipulate that _PARTIAL should only be matched at the end of the string, for instance.
- is invariably case-sensitive in the .NET Framework (though .NET Core offers a case-insensitive overload).

Building on Ansgar's answer, your script can therefore be streamlined as follows:

Param($xmlfile)

$db = ((Get-ChildItem C:\Files -Filter $xmlfile).BaseName -replace '_PARTIAL$').ToUpper()

Note that in PSv3+ this works even if $xmlfile should match multiple files, due to member-access enumeration and the ability of -replace to accept an array of strings as input, the desired substring removal would be performed on the base names of all files, as would the subsequent uppercasing - $db would then receive an array of stripped base names.

How do I strip part of a file name?

2 Answers2