AIX

static const std::string getArg0(void)
    {
#if defined(__hpux__) || defined(__hpux)
    extern char** __argv_value; // see man crt0 on HP-UX.
    return __argv_value[0];
#elif defined(__linux__)
    static std::string argv;
    static bool first = true;
    if (first)
        {
        first = false;
        std::ifstream is("/proc/self/cmdline");
        if (!is)
            argv = "unknown";
        else
            {
            std::ostringstream os;
            char buf;
            while (true)
                {
                is.get(buf);
                if (!is)
                    break;
                if (!isspace(buf))
                    os << buf;
                else
                    break;
                }
            os << std::ends;
            argv = os.str();
            is.close();
            }
        }
        return argv;
#elif defined(_AIX)
    extern char** argv;
    return argv[0];
#else
    return "unknown";
#endif
    }

// -- public -----------------------------------------------------------------
// getProcName()
//
// Determine the process name and return it.
//
// -- implementation ---------------------------------------------------------
// Since this is called before main(), we can't use argv.  But the C run time
// startup code sets argv from the global __argv_value, so just use that.
// ---------------------------------------------------------------------------
TextString LogStream::getProcName(bool useFullPath)
    {
      // LAB - GCC upgrade syntax change
    static TextString fullName(getArg0().c_str());
    static TextString leafOnly(basename((char *)fullName.stringPtr()));
    return useFullPath ? fullName : leafOnly;
    }

truss -o /tmp/hosts-trace bash -c 'echo $0'