In PowerShell, what's the difference between Out-File
and Set-Content
? Or Add-Content
and Out-File -append
?
I've found if I use both against the same file, the text is fully mojibaked .
(A minor second question: >
is an alias for Out-File
, right?)
Here's a summary of what I've deduced, after a few months experience with PowerShell, and some scientific experimentation. I never found any of this in the documentation :(
[ Update: Much of this now appears to be better documented.]
While Out-File
is running, another application can read the log file.
While Set-Content
is running, other applications cannot read the log file. Thus never use Set-Content
to log long running commands.
Out-File
saves in the Unicode
( UTF-16LE
) encoding by default (though this can be specified), whereasSet-Content
defaults to ASCII
( US-ASCII
) in PowerShell 3+ (this may also be specified). In earlier PowerShell versions, Set-Content
wrote content in the Default
(ANSI) encoding.
Editor's note : PowerShell as of version 5.1 still defaults to the culture-specific Default
("ANSI") encoding, despite what the documentation claims. If ASCII were the default, non-ASCII characters such as ü
would be converted to literal ?
, but that is not the case: 'ü' | Set-Content tmp.txt; (Get-Content tmp.txt) -eq '?'
'ü' | Set-Content tmp.txt; (Get-Content tmp.txt) -eq '?'
yields $False
.
PS > $null | out-file outed.txt
PS > $null | set-content set.txt
PS > md5sum *
f3b25701fe362ec84616a93a45ce9998 *outed.txt
d41d8cd98f00b204e9800998ecf8427e *set.txt
This means the defaults of two commands are incompatible, and mixing them will corrupt text, so always specify an encoding.
As Bartek explained, Out-File
saves the fancy formatting of the output, as seen in the terminal. So in a folder with two files, the command dir | out-file out.txt
dir | out-file out.txt
creates a file with 11 lines.
Whereas Set-Content
saves a simpler representation. In that folder with two files, the command dir | set-content sc.txt
dir | set-content sc.txt
creates a file with two lines. To emulate the output in the terminal:
PS > dir | ForEach-Object {$_.ToString()}
out.txt
sc.txt
I believe this formatting has a consequence for line breaks, but I can't describe it yet.
Set-Content
doesn't reliably create an empty file when Out-File
would:
In an empty folder, the command dir | out-file out.txt
dir | out-file out.txt
creates a file, while dir | set-content sc.txt
dir | set-content sc.txt
does not.
Set-Content
takes the filename from the pipeline; allowing you to set a number of files' contents to some fixed value.
Out-File
takes the data as from the pipeline; updating a single file's content.
Set-Content
includes the following additional parameters:
Out-File
includes the following additional parameters:
For more information about what those parameters are, please refer to help; eg get-help out-file -parameter append
.
Out-File
has the behavior of overwriting the output path unless the -NoClobber
and/or the -Append
flag is set. Add-Content
will append content if the output path already exists by default (if it can). Both will create the file if one doesn't already exist.
Another interesting difference is that Add-Content
will create an ASCII encoded file by default and Out-File
will create a little endian unicode encoded file by default.
>
is an alias syntactic sugar for Out-File
. It's Out-File
with some pre-defined parameter settings.
Well, I would disagree... :)
so:
ls | Add-Content test.txt
and
ls | Out-File test.txt
will give you totally different results.
And no, '>' is not alias, it's redirection operator (same as in other shells). And has very serious limitation... It will cut lines same way they are displayed. Out-File has -Width parameter that helps you avoid this. Also, with redirection operators you can't decide what encoding to use.
HTH Bartek
Set-Content
supports -Encoding Byte
, while Out-File
does not.
So when you want to write binary data or result of Text.Encoding#GetBytes()
to a file, you should use Set-Content
.
Out-file -append or ">>" can actually mix two encodings in the same file. Even if the file is originally ascii or ansi, it will add unicode by default to the bottom of it. Add-content will check the encoding and match it before appending. Btw, export-csv defaults to ascii (no accents), and set-content/add-content to ansi.
Wanted to add about difference on encoding:
Windows with PowerShell 5.1:
Linux with PowerShell 7.1:
TL;DR , use Set-Content
as it's more consistent over Out-File
.
Set-Content
behavior is the same over different powershell versions Out-File
as @JagWireZ says produces different encodings for the default settings, even on the same OS(Windows) the docs for powershell 5.1 and powershell 7.3 state that the encoding changed from unicode
to utf8NoBOM
Some issues like Malformed XML arise from using Out-File
, that could of course be fixed by setting the desired encoding, however it's likely to forget to set the encoding and end up with issues.
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