#9143: feature request: way to set actual program argv ----------------------------------------------+---------------------------- Reporter: joeyhess | Owner: Type: feature request | simonmar Priority: normal | Status: new Component: Runtime System | Milestone: Keywords: | Version: 7.8.2 Architecture: Unknown/Multiple | Operating System: Linux Difficulty: Moderate (less than a day) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- It's not currently possible to write a program with ghc that changes its argv, so as to change what the program name/parameters appear to be in ps. An example of a program that does this is sshd, which arranges for the process name to say which user it's serving. For example, "sshd: joey [priv]" I'd like to be able to write such programs using haskell too. Also, I have a haskell program that, due to the way it is executed, has a really horrible display in ps: /usr/local/propellor/docker/android-git-annex- builder.orca.kitenet.net.propellor.shim/lib64/ld-linux-x86-64.so.2 --library-path /usr/local/propellor/docker/android-git-annex- builder.orca.kitenet.net.propellor.shim/lib/x86_64-linux- gnu:/usr/local/propellor/docker/android-git-annex- builder.orca.kitenet.net.propellor.shim/usr/lib/x86_64-linux- gnu:/usr/local/propellor/docker/android-git-annex- builder.orca.kitenet.net.propellor.shim/lib64:/usr/local/propellor/docker /android-git-annex- builder.orca.kitenet.net.propellor.shim/etc/ld.so.conf.d:/usr/local/propellor/docker /android-git-annex-builder.orca.kitenet.net.propellor.shim/usr/lib/x86_64 -linux-gnu/audit:/usr/local/propellor/docker/android-git-annex- builder.orca.kitenet.net.propellor.shim/usr/lib/x86_64-linux-gnu/gconv /usr/local/propellor/propellor That's enough motivation for me to dig into this. :) In rts/RtsMain.c, progargv is set to point to argv. However, it's static, so this cannot be (ab)used from the FFI to change argv. So, a minimal change would be to make progargv not be static, and perhaps give it a more formal name or minimal FFI binding. A GHC-specific library could then use this to modify argv. The haskell interface I'm considering would be: displayArgv :: [String] -> IO () It would need to truncate strings to fit within the available argv space. (This would not affect the argv used by System.Environment, which is a copy of argv.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9143 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler