Comparing strings inside of foreach - string

Question

I want to compare 2 strings in PowerShell. One is the actual date and the other will be read from a file that contains a lot of rows. The row always will contain the same structure, then we can extract a substring for compare the date.
The file will be a plain text. The types of a date and the substring are the same.
MyProblem:
If I execute this code the program doesn't write anything, the Write-Host is not executing, even if the strings are the same. Can someone help me?
$list = Import-Csv C:\file.txt
#actual date
$date = Get-date -Format d
$day = $fecha.Substring(0,2)
$month = $fecha.Substring(3,2)
$year = $fecha.Substring(6,4)
$date = "$year$month$day"
#I do this because if I use $list will return me an pscustomobject object
$file = Get-Content -Path C:\file.txt
#Use a ForEach loop to process all lines in the source file
foreach ($row in $file) {
$sub = $entrada.Substring(7,7)
if ($date-like $sub) {Write-Host "They are equals"}
if ($sub -Match $date) {Write-Host "They are equals"}
if ($date.Equals($sub)) {Write-Host "They are equals"}
if ($date-eq $sub) {Write-Host "They are equals"}
if ($sub -contains $date) {Write-Host "They are equals"}
}

Answer 1

Your reference date string is 8 characters long, but the string you extract from the lines has only 7 characters, so it's unlikely you'll ever get a match. Particularly since you carefully chose your comparisons to avoid even accidental matches. ;) Also, as #arco444 pointed out in the comments to your question, your loop variable $row is never used anywhere inside the loop.
I would suggest to simplify the code to something like this:
$date = Get-Date -f 'yyyyMMdd'
Get-Content -Path 'C:\file.txt' | Where-Object { $_.Substring(7,8) -eq $date }
That would list only those lines from the input file that contain a matching date.
Another option would be to use the Contains() method on each line:
Get-Content -Path 'C:\file.txt' | Where-Object { $_.Contains($date) }
but that would find a matching date anywhere in a line, not just at the given position.
I'd avoid using wildcard (-like) or regular expression (-match) checks, since you want to compare a fixed value, not a pattern. And you can't use the -contains operator, because that one is for checking if an array contains a particular element.

Answer 2

It looks like "entrada" and "row" were intended to refer to the same data item.
Try it like this:
$list = Import-Csv C:\file.txt
#actual date
$date = Get-date -Format d
$day = $fecha.Substring(0,2)
$month = $fecha.Substring(3,2)
$year = $fecha.Substring(6,4)
$date = "$year$month$day"
#I do this because if I use $list will return me an pscustomobject object
$file = Get-Content -Path C:\file.txt
#Use a ForEach loop to process all lines in the source file
foreach ($entrada in $file) {
$sub = $entrada.Substring(7,7)
if ($date-like $sub) {Write-Host "They are equals"}
if ($sub -Match $date) {Write-Host "They are equals"}
if ($date.Equals($sub)) {Write-Host "They are equals"}
if ($date-eq $sub) {Write-Host "They are equals"}
if ($sub -contains $date) {Write-Host "They are equals"}
}