EV_$INTRO Domain/OS EV_$INTRO
NAME
intro - manipulating Domain/OS environment variables
SYNOPSIS (C)
#include <apollo/base.h>
#include <apollo/ev.h>
SYNOPSIS (Pascal)
%include '/sys/ins/base.ins.pas';
%include '/sys/ins/ev.ins.pas';
SYNOPSIS (FORTRAN)
%include '/sys/ins/base.ins.ftn'
%include '/sys/ins/ev.ins.ftn'
DESCRIPTION
The ev_$ calls allow programs to manipulate variables in the process
environment. The process environment is part of the context associated
with each process. The process environment includes a list of name/value
pairs called "environment variables," which are usually used to pass
information from one program to another program running in the same pro-
cess, or from a parent to a child process.
Two common environment variables are USER and PATH; they are present in
nearly all processes. The USER variable is set by the system and identi-
fies the owner of a process; it cannot be modified by descendant
processes. The PATH variable is also initially set by the system. It's
value is a list of directories to be searched for executable files, and
it can be modified by descendent process to broaden or restrict the set
of available programs.
An environment variable is created by assigning a value to it, and it
persists as long as the environment does unless it is explicitly deleted
by the process running in the environment. An environment variable can
be accessed by its name, via ev_$get_var for instance, or by its position
in the environment variable list, via ev_$read_var_entry.
The following is a list of the ev_$ calls.
ev_$delete_var delete an environment variable
ev_$exist_var test an environment variable
ev_$get_var get an environment variable
ev_$read_var_entry read an environment entry
ev_$set_var set an environment variable
Constants
ev_$string_max
The maximum number of bytes in the name or value of an environment
variable.
Data Types
ev_$string_ptr_t
A pointer to type ev_$string_t used to supply the names and values
of environment variables to a program.
ev_$string_t
An array of up to ev_$string_max bytes used to hold the name or
value of an environment variable.