getenv, NLgetenv

Purpose

     Returns the value of an environment variable.

Library

     Standard C Library (libc.a)

Syntax

     char *getenv (name)                       char *NLgetenv (name)
     char *name;                               char *name;
     Description

     The getenv subroutine searches the environment list for a
     string of the form name=value.  Environment variables are
     sometimes  called shell  variables  since  they are  fre-
     quently set with shell commands.

     The NLgetenv  normally searches the environment  for name
     in the  same way as  getenv, except that  special actions
     may be taken if no  environment definition is present for
     name (NULL is  a valid definition) or if a  file meant to
     supercede the current environment  is specified through a
     call to NLgetfile.

     Return Value

     The getenv subroutine  returns a pointer to  the value in
     the current environment if such  a string is present.  If
     such a string is not present, a NULL pointer is returned.

     When no  "override" file is found,  NLgetenv follows this
     procedure:

     1.  The  definition of  name is  returned, if  a non-null
         definition for name exists in the environment.

     2.  If no  definition (or a  null definition) of  name is
         found in the environment definitions, the environment
         variable  NLFILE is  searched for  the pathname  of a
         file containing environment definitions.  These defi-
         nitions are  of the  form parameter=value.   They are
         read directly from the environment and interpreted as
         definitions.

         o   If a non-null definition for name is found, it is
             returned.
         o   If a  null definition  for name  is found,  or if
             there  is  no default  value  for  name, NULL  is
             returned.

     3.  If no non-null  definition for name is  found in this
         file, or if NLFILE is not defined in the environment,
         NLgetenv  returns  a  traditional default  value;  if
         there is no default value for name, NULL is returned.

     If NLgetfile is called  with a superceding file parameter
     before NLgetenv  is called, the search  procedure is dif-
     ferent.  The "override" file is searched; the environment
     of the process is not consulted in this operation:

     1.  If a  non-null definition  for name  is found  in the
         file, then NLgetenv returns the definition.

     2.  If name is not defined in the file, then:

         o   A default definition is returned, if one exists.
         o   If no default definition exists, NLgetenv returns
             NULL.

     Related Information

     In this book:  "NLgetfile," "putenv," and "environment."

     The  sh   command  in   AIX  Operating   System  Commands
     Reference.

     "Overview of International Character Support" in Managing
     the AIX Operating System.