// context-envvar tapset
// Copyright (C) 2010 Pixar Inc. and/or Lars R. Damerow
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.
// <tapsetdescription>
// Context functions provide additional information about where an event occurred. These functions can
//provide information such as a backtrace to where the event occurred and the current register values for the
//processor.
// </tapsetdescription>

/**
 * sfunction env_var - Fetch environment variable from current process
 * @name: Name of the environment variable to fetch
 *
 * Description: Returns the contents of the specified environment value
 * for the current process. If the variable isn't set an empty string
 * is returned.
 */
function env_var:string(name:string)
{
  if (name == "")
    return ""

  env_value = "";
  mm = @cast(task_current(), "task_struct", "kernel<linux/sched.h>")->mm;
  if (mm)
    {
      env_start = @cast(mm, "mm_struct", "kernel<linux/sched.h>")->env_start;
      env_end = @cast(mm, "mm_struct", "kernel<linux/sched.h>")->env_end;
      if (env_start != 0 && env_end != 0)
        {
          len = env_end - env_start;
          cur = user_string2(env_start, "");
          env_name = tokenize(cur, "=");
          while (env_name != name && len > 0)
            {
              env_len = strlen(cur);
              env_start += env_len + 1;
              len -= env_len + 1;
              if (len > 0)
                {
                  cur = user_string2(env_start, "");
                  env_name = tokenize(cur, "=");
                }
              else
                env_name = "";
            }

          if (len > 0)
            env_value = tokenize("", "");
        }
    }
  return env_value;
}