I'm attempting to update the hosts file on a Windows server and trying to do it using a heredoc in powershell.
I can't figure out why my result has extra spaces between every character in each hosts entry.
I'm porting some scripting from Linux.
PS C:\Users\Administrator> cat C:\Users\Administrator\AppData\Local\Temp\etchosts.ps1
@"
127.0.0.1 src.example.com
127.0.0.2 builds.example.com
127.0.0.3 ti.example.com
127.0.0.4 jira.example.com
"@ >>C:\Windows\System32\drivers\etc\hosts
PS C:\Users\Administrator> powershell C:\Users\Administrator\AppData\Local\Temp\etchosts.ps1
PS C:\Users\Administrator> cat C:\Windows\System32\drivers\etc\hosts
# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
1 2 7 . 0 . 0 . 1 s r c . e x a m p l e . c o m
1 2 7 . 0 . 0 . 2 b u i l d s . e x a m p l e . c o m
1 2 7 . 0 . 0 . 3 t i . e x a m p l e . c o m
1 2 7 . 0 . 0 . 4 j i r a . e x a m p l e . c o m
I expected no spaces between all the characters. If there is a "Windows" way to do this, I would appreciate any input/suggestions.
A here-string is just a special form of a PowerShell string literal, and like all strings in PowerShell and .NET (System.String
), their in-memory encoding is always UTF-16.
However, what matters is how you write an (in-memory) string to a file.
>> file
is effectively the same as | Out-File -Append file
, and in Windows PowerShell Out-File
defaults to UTF16-LE encoding ("Unicode"), where each character is (typically) encoded with 2 bytes. What appear to be spaces are actually the NUL
(0x0
) bytes in the 2nd byte of the encoding of each ASCII-range character.
By contrast, C:\Windows\System32\drivers\etc\hosts
is ASCII-encoded (1 byte per character).
To match that encoding, use Add-Content
instead of >>
:
@"
127.0.0.1 src.example.com
127.0.0.2 builds.example.com
127.0.0.3 ti.example.com
127.0.0.4 jira.example.com
"@ | Add-Content C:\Windows\System32\drivers\etc\hosts
Unlike Out-File -Append
, Add-Content
matches the encoding of a file's preexisting content (and, if there is none, defaults to the active ANSI code page's encoding ("Default") in Windows PowerShell, like Set-Content
); in the absence of a BOM, as in this case, ANSI encoding is assumed, but with ASCII-range-only input characters that is effectively the same as ASCII, given that ANSI code pages are a superset of ASCII.
See also:
This answer to a closely related question.
This comprehensive overview of PowerShell's encoding behaviors, including how to change the default encoding for >
/ >>
.
This GitHub suggestion to add a conceptual help topic about character encoding to the official PowerShell documentation.