It is possible; I don't know how compatible this is, but PowerShell treats strings as text and they end up on screen, Bash treats them as commands and tries to run them, and both support the same function definition syntax. So, put a function name in quotes and only Bash will run it, put "exit" in quotes and only Bash will exit. Then write PowerShell code after.
NB. this works because the syntax in both shells overlaps, and your script is simple - run commands and deal with variables. If you try to use more advanced script (if/then, for, switch, case, etc.) for either language, the other one will probably complain.
Save this as dual.ps1 so PowerShell is happy with it, chmod +x dual.ps1 so Bash will run it
#!/bin/bash
function DoBashThings {
wget http://www.example.org/my.script -O my.script
# set a couple of environment variables
export script_source=http://www.example.org
export some_value=floob
# now execute the downloaded script
bash ./my.script
}
"DoBashThings" # This runs the bash script, in PS it's just a string
"exit" # This quits the bash version, in PS it's just a string
# PowerShell code here
# --------------------
Invoke-WebRequest "http://www.example.org/my.script.ps1" -OutFile my.script.ps1
$env:script_source="http://www.example.org"
$env:some_value="floob"
PowerShell -File ./my.script.ps1
then
./dual.ps1
on either system.
Edit: You can include more complex code by commenting the code blocks with a distinct prefix, then having each language filter out its own code and eval it (usual security caveats apply with eval), e.g. with this approach (incorporating suggestion from Harry Johnston ):
#!/bin/bash
#posh $num = 200
#posh if (150 -lt $num) {
#posh write-host "PowerShell here"
#posh }
#bash thing="xyz"
#bash if [ "$thing" = "xyz" ]
#bash then
#bash echo "Bash here"
#bash fi
function RunBashStuff {
eval "$(grep '^#bash' $0 | sed -e 's/^#bash //')"
}
"RunBashStuff"
"exit"
((Get-Content $MyInvocation.MyCommand.Source) -match '^#posh' -replace '^#posh ') -join "`n" | Invoke-Expression
