CODEWITHSUNDEEP
powershell-core
Łukasz Nojek
Łukasz Nojek

Reputation: 1641

Powershell replace multiline doesn't work when matching end of line

I have a problem when replacing a multi line string with the MultiLine option.

I'd expect the following snippet:

@"
abc
---
def
"@ -replace '(?m)^---$', 'AAA'

to result in:

abc
AAA
def

whereas it outputs:

abc
---
def

Why it doesn't work?

Upvotes: 0

Views: 239

Answers (2)

Dmytro
Dmytro

Reputation: 33

You need to use multiline mode also for the new line:

@"
abc
---
def
"@ -replace '(?m)^---(?m)$', 'AAA'

Upvotes: 0

swbbl
swbbl

Reputation: 864

The end of line/string token $ of regex can't match the end of line in regex' multiline mode when CRLF (carriage return 0x0D + line feed 0x0A) is used for line breaks.

Info: This is not the case in non-multiline mode where $ matches the end of string.

For files which are using CRLF as line endings (which is the default behavior of Windows) it's necessary to use \r$, but to be entirely compatible with any file and operating system (like unix/linux, where LF is used), the carriage return should be made optional: \r?$

With PowerShell it's also easily possible to figure out which line endings are in place. The character hex code 0D followed by 0A means CRLF.
Example:

@'
TEST
123
'@ | Format-Hex

#returns:
#
#   Label: String (System.String) <7AFCD388>
#
#           Offset Bytes                                           Ascii
#                  00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
#           ------ ----------------------------------------------- -----
# 0000000000000000 54 45 53 54 0D 0A 31 32 33                      TEST��123

Upvotes: 1

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