To summarize and complement gravity's and Brian Reynolds's helpful answers:
There are two distinct problems with your approach:
Targeting C: probably doesn't (always) do what you want, because C: refers to whatever happens to be the current location (working dir.) on drive C: at the moment.
- To target the root folder of drive C:, you must use
C:\, which I'll assume is what you meant in the remainder of this answer.
Using the -Exclude (and also -Include) parameter with neither -Recurse nor a -Path value of * or ending in \* often yields NO results. Unexpected? Indeed - see below for more.
- Thus,
Get-Item -Path C:\* -Exclude *.txt - note the switch from Get-ChildItem to Get-Item and the * after C:\ - is needed to make your command work for the items located directly in C:\ only.
Background information:
Using the provider-native -Filter parameter is generally preferable to -Include, because:
it is much faster than -Include due to the provider itself performing the filtering at the source, as opposed to letting PowerShell apply the filter later, after all objects have been received.
it doesn't require you to switch to Get-Item and append \* to the -Path parameter value.
Get-ChildItem -Path C:\ -Filter *.txt works fine for matching all *.txt files in the root directory of C:, for instance.
That said, there are caveats:
The wildcard pattern language supported by -Filter has fewer features than PowerShell's - notably, it doesn't support character sets/ranges such as [0-9] - may unexpectedly match short (8.3) filenames, and has other legacy quirks - see this well-researched answer for the gory details.
-Filter supports only a single pattern, whereas -Include supports multiple ones (an array of patterns).
Unfortunately, -Filter is always a positive (inclusionary) filter and therefore cannot be used to provide the functionality of -Exclude.
The implementation of -Include / -Exclude with Get-ChildItem is unintuitive and has pitfalls:
Side note: if you only use one -Include pattern (as opposed to -Exclude), it's easier to append the pattern directly to the -Path argument; e.g.: Get-ChildItem C:\*.txt
tl;dr:
To get predictable behavior with -Include / -Exclude if you're not also using -Recurse (if you are using -Recurse this workaround is not needed):
# IMPORTANT: Workaround isn't needed if you're using -Recurse.
# * "\*" was appended to the input path
# * Get-*ChildItem* was switched to Get-*Item*
Get-Item C:\path\to\* -Include ...
Get-Item C:\path\to\* -Exclude ...
In PowerShell (Core) v7+, if your input paths are literal ones, you can alternatively use Get-ChildItem with -LiteralPath rather than (possibly positionally implied) -Path (use . for the current dir.):
# IMPORTANT: Works in PowerShell (Core) only.
# Note the use of -LiteralPath.
Get-ChildItem -LiteralPath C:\path\to -Include ...
Get-ChildItem -Literalpath C:\path\to -Exclude ...
There's an outright bug in Windows PowerShell where, when -LiteralPath is used, -Include / -Exclude are quietly ignored. This has been fixed in PowerShell (Core) as of (at least) v7.0 (and it's fair to assume that it will not be fixed in Windows PowerShell, which will only receive critical fixes going forward).
-Include and -Exclude do not work as one would intuitively expect, which is the subject of GitHub issue #3304:
-Include and -Exclude modify the leaf (last) path component of the -Path argument, i.e. file or directory names in the case of file-system paths.
That means that the patterns are first applied to the leaf component of the specified folder path itself, before getting applied to the child items, if at all.
If the input path doesn't end in \* and -Recurse is not specified, the implications are as follows:
-Include: If the input path's last path component does not match the -Include pattern(s), the input path itself is excluded (not included), and the path's child items are never looked at - nothing is output.
-Exclude: Analogously, if the input path's last path component does match the -Exclude pattern(s), the input path itself is excluded, and the path's child items are never looked at - nothing is output.
- Targeting a root directory - e.g.,
Get-ChildItem -Path C:\ -Exclude Windows) appears to be broken altogether as of v7.0: it either produces no output at all, or fails on Unix-like platforms, both with -Include and -Exclude, irrespective of the patterns used - see GitHub issue #11649.
As stated, the problem doesn't surface if -Recurse is used, because that forces descending into the input path's subtree, even if the input path itself is not included / excluded.
Unless -Recurse is needed, the only way to get expected behavior is to replace
Get-ChildItem C:\path\to -Include / -Exclude with
Get-Item C:\path\to\* -Include / -Exclude - note the use of Get-Item instead of Get-ChildItem, and that \* was appended to the -Path argument.
- By contrast, if you use
Get-ChildItem * in combination with -Exclude and there are directories among the non-excluded items, Get-ChildItem will unexpectedly output their contents instead; this does not happen with -Include and generally doesn't happen with subdirectory matches by a wildcard expression (-Path argument and/or -Filter argument).
A summary of the problems as of PowerShell 7.2:
GitHub issue #3304 (discussed above): counterintuitive application of -Include / -Exclude patterns only to the input themselves rather than to their children.
GitHub issue #11649: Get-ChildItem -Path <rootPath> -Exclude <anyPattern> unexpectedly produces no output (even though nothing should be excluded, given that the exclusion pattern is normally applied to the input paths, such as / or c:\).
GitHub issue #9126: -Include / -Exclude unexpectedly follow symlinks when -Recurse is used.
GitHub issue #8662: performance problem: -Include / -Exclude are slower(!) than after-the-fact filtering with Where-Object.
A related feature request is GitHub issue #15159, which suggests introducing the ability to exclude subfolder subtrees (as opposed to just excluding the items matching the patterns themselves, but not their children), with a new parameter such as -ExcludeSubtree.
Examples: problematic uses of -Include / -Exclude
Note: To make all commands below work as one would intuitively expect, replace Get-ChildItem C:\Windows with Get-Item C:\Windows\* - note the use of a different cmdlet, Get-Item, and the appended \*.
# HAPPENS TO WORK, BUT IS NOT ROBUST:
# Matches all w* items *inside* C:\Windows, but
# ONLY because w* happens to match 'Windows' - the last input
# path component - too.
Get-ChildItem C:\Windows -Include w*
# HAPPENS TO WORK, BUT IS NOT ROBUST:
# Matches all items whose names *don't* start with a-v *inside* C:\Windows, but
# ONLY because [a-v]* happens not to exclude 'Windows' - the last input
# path component - too.
Get-ChildItem C:\Windows -Exclude [a-v]*
# OUTPUTS NOTHING:
# Because t* doesn't match 'Windows', the child items of
# 'C:\Windows' are not considered.
Get-ChildItem C:\Windows -Include t*
# OUTPUTS NOTHING:
# Because w* matches 'Windows', it is excluded, and
# the child items of 'C:\Windows' are not considered.
Get-ChildItem C:\Windows -Exclude w*
