Replace xBD character to blank value - regex

In powershell, how to replace XBD character to blank space from the text file?

Assuming that xBD refers to the underlying ASCII value, 0xBD, it should be as easy as:
$string.Replace("$(0xBD -as [char])","")
For multiple lines (eg. an entire text file), use the -replace regex operator.
The syntax for the -replace operator is:
"string(s)" -replace "regex pattern","replacement"
If you omit the "replacement" argument, the characters matched by the regex pattern will simply be removed.
The proper regex pattern in .NET to match that character would be \xBD:
(Get-Content .\myfile.txt) -replace '\xBD' | Set-Content .\mynewfile.txt

Related

Replace text + optional newline in file

I've been through other similar questions and tried their advice, but it wouldn't help.
I'm trying to delete a specific line of text in a text file.
My code which works
(Get-Content -Path "MyPath.txt" -Raw).Replace('this is the line', '') | Set-Content "MyPath.txt" -Encoding UTF8
Now this works but leaves an ugly empty line in the text file. I wanted to also replace an optional newline character by adding this regex at the end of the line
\n?
and this wouldn't work. The other threads made other recommendations and I've tried all combinations but just can't match. I'm using windows style ending (CRLF)
Both using -Raw and not using it
\n
\r\n
`n
`r`n
I haven't even added the regex question mark at the end (or non-capturing group in case it needs the \r\n syntax).
The [string] type's .Replace() method doesn't support regexes (regular expressions), whereas PowerShell's -replace operator does.
However, the simplest solution in this case is to take advantage of the fact that the -ne operator acts as a filter with an array-valued LHS (as other comparison operators do):
#(Get-Content -Path MyPath.txt) -ne 'this is the line' |
Set-Content MyPath.txt -Encoding UTF8
Note how Get-Content is called without -Raw in order to return an array of lines, from which -ne then filters out the line of (non)-interest; #(...), the array-subexpression operator ensures that the output is an array even if the file happens to contain just one line.
The assumption is that string 'this is the line' matches the whole line (case-insensitively).
If that is not the case, instead of -ne you could use -notlike with a wildcard expression or -notmatch with a regex (e.g.,
-notmatch 'this is the line' or -notlike '*this is the line')

Powershell regex match sequence doesn't work although it matches in Sublime Text find and replace

I am trying to create a Powershell regex statement to remove the top five lines of this output from a git diff file that has already been modified with Powershell regex.
[1mdiff --git a/uk1.adoc b/uk2.adoc</span>+++
[1mindex b5d3bf7..90299b8 100644</span>+++
[1m--- a/uk1.adoc</span>+++
[1m+++ b/uk2.adoc</span>+++
[36m## -1,9 +1,9 ##</span>+++
= Heading
Body text
Image shown because binary code doesn't show in the text
The following statement matches the text so the '= Heading' line is placed at the top of the page if I replace with nothing.
^[^=]*.[+][\n]
But in Powershell, it isn't matching the text.
Get-Content "result2.adoc" | % { $_ -Replace '^[^=]*.[+][\n]', '' } | Out-File "result3.adoc";
Any ideas about why it doesn't work in Powershell?
My overall goal is to create a diff file of two versions of an AsciiDoc file and then replace the ASCII codes with HTML/CSS code to display the resulting AsciiDoc file with green/red track changes.
The simplest - and faster - approach is to read the input file as a single, multiline string with Get-Content -Raw and let the regex passed to -replace operate across multiple lines:
(Get-Content -Raw result2.adoc) -replace '(?s)^.+?\n(?==)' |
Set-Content result3.adoc
(?s) activates in-line option s which makes . match newline (\n) characters too.
^.+?\n(?==) matches from the start of the string (^) any number of characters (including newlines) (.+), non-greedily (?)
until a newline (\n) followed by a = is found.
(?=...) is a look-ahead assertion, which matches = without consuming it, i.e., without considering it part of the substring that matched.
Since no replacement operand is passed to -replace, the entire match is replace with the implied empty string, i.e., what was matched is effectively removed.
As for what you tried:
The -replace operator passes its LHS through if no match is found, so you cannot use it to filter out non-matching lines.
Even if you match an undesired line in full and replace it with '' (the empty string), it will show up as an empty line in the output when sent to Set-Content or Out-File (>).
As for your specific regex, ^[^=]*.[+][\n] (whether or not the first ^ is followed by an ESC (0x1b) char.):
[\n] (just \n would suffice) tries to match a newline char. after a literal + ([+]), yet lines read individually with Get-Content (without -Raw) by definition are stripped of their trailing newline, so the \n will never match; instead, use $ to match the end of a line.
Instead of % (the built-in alias for the ForEach-Object cmdlet) you could have used ? (the built-in alias for the Where-Object cmdlet) to perform the desired filtering:
Get-Content result2.adoc | ? { $_ -notmatch '^\e\[' }
$_ -notmatch '^\e[' returns $True only for lines that don't start (^) with an ESC character (\e, whose code point is 0x1b) followed by a literal (\) [, thereby effectively filtering out the lines before the = Heading line.
However, the multi-line -replace command at the top is a more direct and faster expression of your intent.
Here is the code I ended up with after help from #mklement0. This Powershell script creates MS Word-style track changes for two versions of an AsciiDoc file. It creates the Diff file, uses regex to replace ASCII codes with HTML/CSS tags, removes the Diff header (thank you!), uses AsciiDoctor to create an HTML file and then PrinceXML to create a PDF file of the output that I can send to document reviewers.
git diff --color-words file1.adoc file2.adoc > result.adoc;
Get-Content "result.adoc" | % {
$_ -Replace '(=+ ?)([A-Za-z\s]+)(\[m)', '$1$2' `
-Replace '\[32m', '+++<span style="color: #00cd00;">' `
-Replace '\[31m', '+++<span style="color: #cd0000; text-decoration: line-through;">' `
-Replace '\[m', '</span>+++' } | Out-File -encoding utf8 "result2.adoc" ;
(Get-Content -Raw result2.adoc) -replace '(?s)^.+?\n(?==)', '' | Out-File -encoding utf8 "result3.adoc" ;
asciidoctor result3.adoc -o result3.html;
prince result3.html --javascript -o result3.pdf;
Read-Host -Prompt "Press Enter to exit"
Here's a screenshot of the result using some text from Wikipedia:

Regular Expressions in powershell split

I need to strip out a UNC fqdn name down to just the name or IP depending on the input.
My examples would be
\\tom.overflow.corp.com
\\123.43.234.23.overflow.corp.com
I want to end up with just tom or 123.43.234.23
I have the following code in my array which is striping out the domain name perfect, but Im still left with \\tom
-Split '\.(?!\d)')[0]
Your regex succeeds in splitting off the tokens of interest in principle, but it doesn't account for the leading \\ in the input strings.
You can use regex alternation (|) to include the leading \\ at the start as an additional -split separator.
Given that matching a separator at the very start of the input creates an empty element with index 0, you then need to access index 1 to get the substring of interest.
In short: The regex passed to -split should be '^\\\\|\.(?!\d)' instead of '\.(?!\d)', and the index used to access the resulting array should be [1] instead of [0]:
'\\tom.overflow.corp.com', '\\123.43.234.23.overflow.corp.com' |
ForEach-Object { ($_ -Split '^\\\\|\.(?!\d)')[1] }
The above yields:
tom
123.43.234.23
Alternatively, you could remove the leading \\ in a separate step, using -replace:
'\\tom.overflow.corp.com', '\\123.43.234.23.overflow.corp.com' |
ForEach-Object { ($_ -Split '\.(?!\d)')[0] -replace '^\\\\' }
Yet another alternative is to use a single -replace operation, which does not require a ForEach-Object call (doesn't require explicit iteration):
'\\tom.overflow.corp.com', '\\123.43.234.23.overflow.corp.com' -replace
'?(x) ^\\\\ (.+?) \.\D .+', '$1'
Inline option (?x) (IgnoreWhiteSpace) allows you to make regexes more readable with insignificant whitespace: any unescaped whitespace can be used for visual formatting.
^\\\\ matches the \\ (escaped with \) at the start (^) of each string.
(.+?) matches one or more characters lazily.
\.\D matches a literal . followed by something other than a digit (\d matches a digit, \D is the negation of that).
.+ matches one or more remaining characters, i.e., the rest of the input.
$1 as the replacement operand refers to what the 1st capture group ((...)) in the regex matched, and, given that the regex was designed to consume the entire string, replaces it with just that.
I'm stealing Lee_Daileys $InSTuff
but appending a RegEx I used recently
$InStuff = -split #'
\\tom.overflow.corp.com
\\123.43.234.23.overflow.corp.com
'#
$InStuff |ForEach-Object {($_.Trim('\\') -split '\.(?!\d{1,3}(\.|$))')[0]}
Sample Output:
tom
123.43.234.23
As you can see here on RegEx101 the dots between the numbers are not matched
The Select-String function uses regex and populates a MatchInfo object with the matches (which can then be queried).
The regex "(\.?\d+)+|\w+" works for your particular example.
"\\tom.overflow.corp.com", "\\123.43.234.23.overflow.corp.com" |
Select-String "(\.?\d+)+|\w+" | % { $_.Matches.Value }
while this is NOT regex, it does work. [grin] i suspect that if you have a really large number of such items, then you will want a regex. they do tend to be faster than simple text operators.
this will get rid of the leading \\ and then replace the domain name with .
# fake reading in a text file
# in real life, use Get-Content
$InStuff = -split #'
\\tom.overflow.corp.com
\\123.43.234.23.overflow.corp.com
'#
$DomainName = '.overflow.corp.com'
$InStuff.ForEach({
$_.TrimStart('\\').Replace($DomainName, '')
})
output ...
tom
123.43.234.23

Using powershell to search for a pattern

I am trying to write a powershell script to search for a pattern in a text file. Specifically I am looking at reading a file line by line and returning any line that has a space at the 32nd character position.
I have this so far but it just returns all lines that have white space. I need to narrow it down to the 32nd position
Get-Content -path C:\VM_names.txt | Where-Object {$_ -match "\s+"}
Use this pattern:
-match '^.{31} '
Explanation:
^ - beginning of the string
. - any character
{31} - repeated 31 times
- a space
This is actually really easy to do. By default, Get-Content reads a text file as an array of strings (individual lines), unless you use the -Raw parameter, which reads it as a single string. You can use the -match PowerShell operator to "match" the lines that meet your regular expression.
(Get-Content -Path c:\VM_names.txt) -match '^.{31}\s'
The result of the above command is an array of lines that match the desired regular expression.
NOTE: The call to Get-Content must be wrapped in parentheses, otherwise the PowerShell parser will think that -match is a parameter on that command.
NOTE2: As a good practice, use single quotes around strings, unless you specifically know that you need double quotes. You'll save yourself from accidental interpolation.

Powershell Regex acting per-line rather than on entire string

Given foo.txt
this is a file
it has some text
the text has three lines
The following regex replacement
(get-content -raw foo.txt) -replace ".*", "hello" | write-output
produces the output
hellohello
hellohello
hellohello
rather than the desired
hello
My understanding was that get-content returns the content as an array of strings, one per line. The -raw flag replaces this behavior with returning the contents as a single string. As far as I know, ".*" should match the entire string, but instead it matches twice on each line.
Please advise.
Use the inline (?s) (dotall) modifier which forces . to span across newlines.
(Get-Content .\foo.txt -Raw) -replace "(?s).+", "hello"
Example:
PS> $data = Get-Content .\foo.txt -Raw
PS> $data
this is a file
it has some text
the text has three lines
PS> $data -replace "(?s).+", "hello"
hello
I can't explain it other than to say that . appears not to be matching newline characters so you get one match for each complete line then one match for the zero characters at the end of each line.
This also explains the .+ behavior of hello once per-line.
You can "fix" this by using a better pattern that does match the newline characters.
(Get-Content -raw .\foo.txt) -replace "(.|\r|\n)+", "hello"
From https://stackoverflow.com/a/13674250/1252649,
The trick around DotAll mode is to use [\s\S] instead of .. This character class matches any character ...
Of course, this raises the question as to what exactly . is supposed to match other than 'any character'.