How to parse string in powershell - string

Question

I have a Powershell command that outputs multiple lines.
I want to output only one line that contains the name of a .zip file.
Currently, all lines are returned when substring .zip is found:
$p.Start() | Out-Null
$p.WaitForExit()
$output = $p.StandardOutput.ReadToEnd()
$output += $p.StandardError.ReadToEnd()
foreach($line in $output)
{
if($line.Contains(".zip"))
{
$line
}
}

Answer 1

Since you're using .ReadToEnd(), $output receives a single, multi-line string, not an array of lines.
You must therefore split that string into individual lines yourself, using the -split operator.
You can then apply a string-comparison operator such as -match or -like directly to the array of lines to extract matching lines:
# Sample multi-line string.
$output = #'
line 1
foo.zip
another line
'#
$output -split '\r?\n' -match '\.zip' # -> 'foo.zip'
-split is regex-based, and regex \r?\n matches newlines (line breaks) of either variety (CRLF, as typical on Windows, as well as LF, as typical on Unix-like platforms).
-match is also regex-based, which is why the . in \.zip is \-escaped, given that . is a regex metacharacter (it matches any character other than LF by default).
Note that -match, like PowerShell in general, is case-insensitive by default, so both foo.zip and foo.ZIP would match, for instance;
if you do want case-sensitivity, use -cmatch.
As an aside:
I wonder why you're running your command via a [System.Diagnostics.Process] instance, given that you seem to be invoking synchronously while capturing its standard streams.
PowerShell allows you to do that much more simply by direct invocation, optionally with redirection:
$output = ... 2>&1