I can manually open up PowerShell and run
wsl
ip addr show eth0 | grep 'inet\b' | awk '{print $2}' | cut -d/ -f1
To get the IP address of the Ubuntu instance. But when I try to write a script for this (100 different ways) I always get some kind of error. This is an example
$command = "ip addr show eth0 | grep 'inet\b' | awk '{print $2}' | cut -d/ -f1"
$ip = Invoke-Expression "wsl $command"
Which gives an error about grep.
Call wsl.exe via the -e option and specify bash as the executable, which allows you to use the latter's -c option with a command line specified as a single string:
# Note the need to escape $ as `$
# to prevent PowerShell from interpolating it up front inside "..."
$command = "ip addr show eth0 | grep 'inet\b' | awk '{print `$2}' | cut -d/ -f1"
wsl -e bash -c $command
A note re the choice of string literals on the PowerShell side:
Using "..." quoting rather than '...' quoting is convenient if the text contains ' characters, because it obviates the need for escaping - ditto for the inverse scenario: using '...' quoting for text that contains " chars.
However, as in POSIX-compatible shells such as Bash, the choice of the enclosing quoting characters matters in PowerShell, because the resulting behavior differs:
'...' is a verbatim (single-quoted) string.
' chars. must be emulated with '\'', PowerShell does support direct escaping, namely with ''"..." is an expandable (double-quoted) string, i.e. subject to string interpolation for substrings that start with $
$ chars. to be used verbatim (literally) require escaping as \$, in PowerShell you must use `$, using `, the so-called backtick, PowerShell's escape character.