问题
I am trying to extract each line starting with "%%" in all files in a folder and then copy those lines to a separate text file. Currently using this code in PowerShell code, but I am not getting any results.
$files = Get-ChildItem "folder" -Filter *.txt
foreach ($file in $files)
{
if ($_ -like "*%%*")
{
Set-Content "Output.txt"
}
}
回答1:
I think that mklement0's suggestion to use Select-String
is the way to go. Adding to his answer, you can pipe the output of Get-ChildItem
into the Select-String
so that the entire process becomes a Powershell one liner.
Something like this:
Get-ChildItem "folder" -Filter *.txt | Select-String -Pattern '^%%' | Select -ExpandProperty line | Set-Content "Output.txt"
回答2:
The Select-String
cmdlet offers a much simpler solution (PSv3+ syntax):
(Select-String -Path folder\*.txt -Pattern '^%%').Line | Set-Content Output.txt
Select-String
accepts a filename/path pattern via its-Path
parameter, so, in this simple case, there is no need forGet-ChildItem
.- If, by contrast, you input file selection is recursive or uses more complex criteria, you can pipe
Get-ChildItem
's output toSelect-String
, as demonstrated in Dave Sexton's helpful answer. - Note that, according to the docs,
Select-String
by default assumes that the input files are UTF-8-encoded, but you can change that with the-Encoding
parameter; also consider the output encoding discussed below.
- If, by contrast, you input file selection is recursive or uses more complex criteria, you can pipe
Select-String
's-Pattern
parameter expects a regular expression rather than a wildcard expression.^%%
only matches literal%%
at the start (^
) of a line.Select-String
outputs[Microsoft.PowerShell.Commands.MatchInfo]
objects that contain information about each match; each object's.Line
property contains the full text of an input line that matched.Set-Content Output.txt
sends all matching lines to single output fileOutput.txt
Set-Content
uses the system's legacy Windows codepage (an 8-bit single-byte encoding - even though the documentation mistakenly claims that ASCII files are produced).
If you want to control the output encoding explicitly, use the-Encoding
parameter; e.g.,... | Set-Content Output.txt -Encoding Utf8
.- By contrast,
>
, the output redirection operator always creates UTF-16LE files (an encoding PowerShell callsUnicode
), as doesOut-File
by default (which can be changed with-Encoding
).
Also note that>
/Out-File
apply PowerShell's default formatting to the input objects to obtain the string representation to write to the output file, whereasSet-Content
treats the input as strings (calls.ToString()
on input objects, if necessary). In the case at hand, since all input objects are already strings, there is no difference (except for the character encoding, potentially).
As for what you've tried:
$_
inside yourforeach ($file in $files)
refers to a file (a[System.IO.FileInfo]
object), so you're effectively evaluating your wildcard expression*%%*
against the input file's name rather than its contents.Aside from that, wildcard pattern
*%%*
will match%%
anywhere in the input string, not just at its start (you'd have to use%%*
instead).The
Set-Content "Output.txt"
call is missing input, because it is not part of a pipeline and, in the absence of pipeline input, no-Value
argument was passed.- Even if you did provide input, however, output file
Output.txt
would get rewritten as a whole in each iteration of yourforeach
loop.
- Even if you did provide input, however, output file
回答3:
ls *.txt | %{
$f = $_
gc $f.fullname | {
if($_.StartWith("%%") -eq 1){
$_ >> Output.txt
}#end if
}#end gc
}#end ls
Alias
ls - Get-ChildItem
gc - Get-Content
% - ForEach
$_ - Iterator variable for loop
>> - Redirection construct
# - Comment
http://ss64.com/ps/
回答4:
First you have to use
Get-Content
in order to get the content of the file. Then you do the string match and based on that you again set the content back to the file. Use get-content and put another loop inside the foreach to iterate all the lines in the file.
I hope this logic helps you
来源:https://stackoverflow.com/questions/41052831/extract-lines-matching-a-pattern-from-all-text-files-in-a-folder-to-a-single-out