Environment Variables — GetVar, SetVar

Overview

AmigaDOS supports both local (per-process) and global (system-wide) environment variables. Local variables are stored in the process's pr_LocalVars MinList; global variables are stored as files in ENV: (RAM-backed) and ENVARC: (persistent on disk).

API

LVO	Function	Description
−900	`GetVar(name, buf, size, flags)`	Read a variable
−906	`SetVar(name, buf, size, flags)`	Set or create a variable
−912	`DeleteVar(name, flags)`	Remove a variable
−918	`FindVar(name, type)`	Find a LocalVar node

Flags

/* dos/var.h — NDK39 */
#define GVF_GLOBAL_ONLY   0x100   /* search only ENV: */
#define GVF_LOCAL_ONLY    0x200   /* search only pr_LocalVars */
#define GVF_BINARY_VAR    0x10    /* treat value as binary data */
#define GVF_DONT_NULL_TERM 0x20   /* don't null-terminate result */
#define LV_VAR            0       /* standard variable */
#define LV_ALIAS          1       /* shell alias */

Usage

/* Set a global variable: */
SetVar("EDITOR", "ed", -1, GVF_GLOBAL_ONLY);

/* Read it back: */
char buf[256];
if (GetVar("EDITOR", buf, sizeof(buf), 0) >= 0) {
    Printf("EDITOR = %s\n", buf);
}

/* Delete: */
DeleteVar("EDITOR", GVF_GLOBAL_ONLY);

Storage Locations

Scope	Storage	Persistent?
Local	`pr_LocalVars` MinList (in-memory)	No — dies with process
Global (volatile)	`ENV:` — assign to `RAM:Env/`	No — lost on reboot
Global (persistent)	`ENVARC:` — assign to `SYS:Prefs/Env-Archive/`	Yes — survives reboot

The startup-sequence copies ENVARC: to ENV: at boot.

References

NDK39: dos/var.h
ADCD 2.1: GetVar, SetVar, DeleteVar