move-item doesn't work in loop - loops

Question

ls *.gif | Foreach { $newname = $_.Name -replace '\[','' -replace '\]',''
write-host $_.Name $newname
move-Item -Path $_.Name -Destination $newname; }
ls *.gif
So while trying to help someone rename files with [], I found out move-item doesn't work in a loop. It seems to work just fine outside the loop.
Ideas?

Answer 1

Update: Based on the comment below, I want to clarify this: The special characters in the file names require you to use -LiteralPath parameter. -Path cannot handle those characters. Outside a loop, -Path works since you are escapting the special characters using `. This isn't possible when walking through a collection.
In a loop, you need to use -LiteralPath parameter instead of -Path.
-LiteralPath <string[]>
Specifies the path to the current location of the items. Unlike Path, the value of
LiteralPath is used exactly as it is typed. **No characters are interpreted as
wildcards. If the path includes escape characters, enclose it in single quotation
marks.** Single quotation marks tell Windows PowerShell not to interpret any
characters as escape sequences.
SO, this will be:
GCI -Recurse *.txt | % { Move-Item -LiteralPath $_.FullName -Destination "SomenewName" }

Answer 2

If you use the pipeline binding feature of PowerShell, you can make this much simpler and eliminate the need for the explicit Foreach-Object e.g.:
ls *.gif | Move-Item -Destination {$_ -replace '\[|\]',''} -WhatIf
This works because the LiteralPath parameter is set up to bind ByPropertyName. However you may wonder, where does it get a property by the name of "LiteralPath" from on the output of Get-ChildItem (alias ls). Well it doesn't find that property name, however the LiteralPath parameter has an alias of PSPath defined which does exist on each object output by Get-ChildItem. That's how it binds to the LiteralPath paramter. The other speed tip here is that because the Destination parameter is also pipeline bound (ByPropertyName), you can use a scriptblock to provide the value. And inside that scriptblock you have access to the pipeline object.
Inside the scriptblock, this uses the -replace operator to come up with the new name based on the original full name. While I could have used $_.FullName or even $_.Name in this case (assuming you want to essentially rename the files within the same dir), I use just $_. Since -replace is a string operator, it will coerce $_ to a string before using it. You can see what this would be by executing:
ls *.gif | Foreach {"$_"}
Which is the full path in this case but you have to be careful because you don't always get the full path e.g.:
ls | Foreach {"$_"}
displays just the filename. In your examples (rename to same dir) this doesn't matter but in other cases it does. It is probably a good practice just to be explicit and use $_.Name or $_.FullName in a script but when hacking this stuff out at the console, I tend to use just $_. The saying: it's a sharp stick, don't poke your eye out applies here. :-)

Answer 3

You can find the "official" informations about the role of "[" in Path strings on this Microsoft article.
Or look in google for : Windows PowerShell Tip of the Week : "Taking Things (Like File Paths) Literally".
The only tip wich was not clear for me is that Rename-Item does not support LiteralPath, and that we can use Move-Item to rename files or directories.
JP

Answer 4

This worked for me (atleast in my situation.
Move-Item -literalpath $_.FullName -Destination ( ( ( (Join-Path -Path (Get-Location) -ChildPath $_.BaseName) -replace "\[","`[") -replace "\]","`]") )
Had hundreds of movies and it associated subtitles stored without folders. Decided to put each of the movies and subtitles in their own folders
Full Code
Get-ChildItem -File | %
{
if(Test-Path -LiteralPath ( Join-Path -Path (Get-Location) -ChildPath $_.BaseName ))
{
Move-Item -literalpath $_.FullName -Destination ( ( ( (Join-Path -Path (Get-Location) -ChildPath $_.BaseName) -replace "\[","`[") -replace "\]","`]") )
}
else
{
New-Item ( Join-Path -Path (Get-Location) -ChildPath $_.BaseName ) -ItemType Directory
Move-Item $_ -Destination ( Join-Path -Path (Get-Location) -ChildPath $_.BaseName )
}
}