Process environment
===================

These procedures are exported by the structures posix & posix-process-data.

 -- procedure: get-process-id returns process-id
 -- procedure: get-parent-process-id returns process-id
     These return the POSIX processes, process id of the current process or the current process's parent, respectively.

 -- procedure: get-user-id returns user-id
 -- procedure: get-effective-user-id returns user-id
 -- procedure: set-user-id! user-id returns unspecified
 -- procedure: get-group-id returns group-id
 -- procedure: get-effective-group-id returns group-id
 -- procedure: set-group-id! group-id returns unspecified
     These access the original and effective POSIX users and groups, user & group ids of the current process.  The effective ids may be set, but not the original ones.

 -- procedure: get-groups returns group-id list
 -- procedure: get-login-name returns string
     Get-groups returns a list of the supplementary groups of the current process.  Get-login-name returns a user name for the current process.

 -- procedure: lookup-environment-variable string returns string or #f
 -- procedure: environment-alist returns alist
     Lookup-environment-variable looks up its argument in the environment list of the current process and returns the corresponding string, or #f if there is none.  Environment-alist returns the entire environment as a list of (NAME-STRING . VALUE-STRING) pairs.