How do i create an argfile for use with javac in Powershell?

Question

I have read this documentation including the section that exemplifies Command Line Argument Files but can't figure out how to get it working in PowerShell. Here's what I have done:

First, I can compile a Driver.java file using (in windows PowerShell, javac version 17.0.3):

>>javac Driver.java

But, I would like to figure out how to use argument files (@filename).

I have tried to create a file called files.txt with 1 entry in it listed as Driver.java and then use javac with @file to specify what to compile:

PS-pluto>>dir -n *.java >files
PS-pluto>javac @files

I tried creating files, and files.txt. Driver.java is definitely the entry, but the javac command doesn't work. I am running this from the folder where files and Driver are located.

I read the answer to this question which indicated that I needed to add quotes, and tried this (again, with and without .txt):

PS-pluto>>dir -n *.java >files
PS-pluto>>javac "@files"

This may work, but doesn't solve the problem. Now I get a new error:

error: invalid flag:  ■Driver.java

I have looked for hidden formatting in my txt file and only see the line return at the end of Driver.java. Not sure what is wrong?

I know in this simplistic case using an argument file is overkill, but I am simply trying to figure out how it works...and cannot.

NOTE: I already know how to compile this in an IDE or with a build tool. I am trying to figure out how to do this in PowerShell, and admittedly, I am a novice PowerShell user.

Answer 1

• An unquoted @ at the start of an argument is a PowerShell metacharacter and therefore needs to either be escaped as `@ or enclosed in a string literal.

• In Windows PowerShell, > creates "Unicode" (UTF-16LE) files by default, which javac most likely cannot handle.

  • In PowerShell (Core) 7+, BOM-less UTF8 is now the (consistent) default, so > would work as is.

  • In Windows PowerShell, the simplest solution is to pipe to Set-Content -Encoding Ascii, assuming that the file names contain ASCII-range characters only.

# Create file "files" as an ASCII file.
# Note: The Get-ChildItem call is `dir -n *.java` fully spelled out.
Get-ChildItem -Name *.java | Set-Content -Encoding Ascii files

# Escape @ as `@ to treat it literally.
javac `@files

If the file names contain non-ASCII characters and javac requires BOM-less UTF-8 encoding, more work is needed, because in Windows PowerShell you cannot directly create BOM-less UTF-8 files - see this answer.