ForEach
is documented as an alias of ForEach-Object
. When I use Get-Alias ForEach
it tells that it is in alias of ForEach-Object
.
But,
ForEach-Object
Accepts parameters such as Begin Process and End, where ForEach
doesn't accept them.
When we call ForEach-Object
without any thing it prompts for parameter Process, and on calling ForEach
it leaves a nested prompt with >>
.
%
and ForEach
behave same, but ForEach-Object
don't.
Here my questions are:
Is ForEach
really an alias of ForEach-Object
?
Which is better, ForEach
or ForEach-Object
?
Please share your thoughts.
Thank you!
There are two distinct underlying constructs :
The ForEach-Object
cmdlet
foreach
, which just so happens to match the name of the distinct foreach
statement (see next point). The foreach
loop statement (akin to the lesser used for
statement).
What foreach
refers to depends on the parsing context - see about_Parsing
:
In argument mode (in the context of a command ), foreach
is ForEach-Object
's alias.
In expression mode (more strictly: statement mode in this case), foreach
is the foreach
loop statement .
As a cmdlet , ForEach-Object
operates on pipeline input .
$_
variable . As a language statement , the foreach
loop operates on variables and expressions (which may include output collected from commands).
Use it to process already-collected-in-memory results efficiently, via a self-chosen iterator variable (eg, $num
in foreach ($num in 1..3) { ... }
); doing so is noticeably faster than processing via ForEach-Object
.
Note that you cannot send outputs from a foreach
statement directly to the pipeline, because PowerShell's grammar doesn't permit it; for streaming output to the pipeline, wrap a foreach
statement in & { ... }
. (By contrast, simple expressions (eg, 1..3
) can be sent directly to the pipeline).
For more information, a performance comparison and a discussion of the tradeoffs (memory use vs. performance), including the .ForEach()
array method , see this answer .
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