Check if the last line in a file is empty in PowerShell - powershell

Question

I want to add some content to a file in a new line.
But add-content appends a string to last line if there is no new line symbol at the end.
E.g. if I want to add AAA string and if I have a file file1.txt
my last line(last cursor position here)
the result will be
my last lineAAA
On the other hand, if I use file2.txt
my last line
(last cursor position here)
the command will result in
my last line
AAA
So I need to check if the last line is empty or not. If it's not empty I will just add `n symbol to the string.
But if I run the commands
$lastLine = get-content $filename -Tail 1
if($lastLine.Length -ne 0) { ... }
it will always return me a length of not empty string even if my last line contains no symbols.
How can I check if my last line is empty ?

Answer 1

You could opt to start adding newlines to the file and for the first line to add do
$file = 'D:\Test\Blah.txt'
$firstLine = 'AAA'
Add-Content -Path $file -Value ("{0}`r`n{1}" -f (Get-Content -Path $file -Raw).TrimEnd(), $firstLine)
After that first line, you can simply keep using Add-Content which always appends an newline (unless you tell it not to do that with switch -NoNewline).
Seeing your comment, you can test the length of the last line like this:
$file = 'D:\Test\Blah.txt'
$lastLine = ((Get-Content -Path $file -Raw) -split '\r?\n')[-1]
# $lastLine.Length --> 0
if($lastLine.Length -ne 0) { ... }
The -Raw switch tells Get-Content to read the file as a whole in a single string. Split this string into separate lines with -split '\r?\n' and you'll get an array, including the last empty line

Answer 2

When you use "Get-Content -Tail 1", it will always recover the last "non empty" line.
# -----------------
# Your method returns the same line even if the file contains an empty line at the end of the file
# -----------------
$lastEmptyLine = Get-Content "test_EmptyLine.txt" -Tail 1
$lastNonEmptyLine = Get-Content "test_NonEmptyLine.txt" -Tail 1
($lastEmptyLine -match '(?<=\r\n)\z')
#False
($lastNonEmptyLine -match '(?<=\r\n)\z')
#False
So if you want to keep the "Test" method (and not simply use Add-Content) you could use the following method :
# -----------------
# This method can tell you if a file finishes by an empty line or not
# -----------------
$contentWithEmptyLine = [IO.File]::ReadAllText("test_EmptyLine.txt")
$contentWithoutEmptyLine = [IO.File]::ReadAllText("test_NonEmptyLine.txt")
($contentWithEmptyLine -match '(?<=\r\n)\z')
#True
($contentWithoutEmptyLine -match '(?<=\r\n)\z')
#False
# -----------------
# You can also use Get-Content with Raw option
# -----------------
$rawContentWithEmptyLine = Get-Content "test_EmptyLine.txt" -Raw
$rawContentWithoutEmptyLine = Get-Content "test_NonEmptyLine.txt" -Raw
($rawContentWithEmptyLine -match '(?<=\r\n)\z')
#True
($rawContentWithoutEmptyLine -match '(?<=\r\n)\z')
#False
-Raw Ignores newline characters and returns the entire contents of a file in one string with the newlines preserved. By default, newline
characters in a file are used as delimiters to separate the input into
an array of strings. This parameter was introduced in PowerShell 3.0.
References :
Get-Content (Microsoft.PowerShell.Management)
Check CRLF at the end of every file
about_Comparison_Operators - PowerShell
Regular expression - Wikipedia