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68 lines
1.8 KiB
Markdown
68 lines
1.8 KiB
Markdown
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[← Home](../README.md) · [AmigaDOS](README.md)
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# Environment Variables — GetVar, SetVar
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## Overview
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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).
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---
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## API
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| LVO | Function | Description |
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|---|---|---|
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| −900 | `GetVar(name, buf, size, flags)` | Read a variable |
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| −906 | `SetVar(name, buf, size, flags)` | Set or create a variable |
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| −912 | `DeleteVar(name, flags)` | Remove a variable |
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| −918 | `FindVar(name, type)` | Find a LocalVar node |
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### Flags
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```c
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/* dos/var.h — NDK39 */
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#define GVF_GLOBAL_ONLY 0x100 /* search only ENV: */
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#define GVF_LOCAL_ONLY 0x200 /* search only pr_LocalVars */
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#define GVF_BINARY_VAR 0x10 /* treat value as binary data */
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#define GVF_DONT_NULL_TERM 0x20 /* don't null-terminate result */
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#define LV_VAR 0 /* standard variable */
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#define LV_ALIAS 1 /* shell alias */
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```
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---
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## Usage
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```c
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/* Set a global variable: */
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SetVar("EDITOR", "ed", -1, GVF_GLOBAL_ONLY);
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/* Read it back: */
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char buf[256];
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if (GetVar("EDITOR", buf, sizeof(buf), 0) >= 0) {
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Printf("EDITOR = %s\n", buf);
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}
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/* Delete: */
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DeleteVar("EDITOR", GVF_GLOBAL_ONLY);
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```
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---
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## Storage Locations
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| Scope | Storage | Persistent? |
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|---|---|---|
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| Local | `pr_LocalVars` MinList (in-memory) | No — dies with process |
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| Global (volatile) | `ENV:` — assign to `RAM:Env/` | No — lost on reboot |
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| Global (persistent) | `ENVARC:` — assign to `SYS:Prefs/Env-Archive/` | Yes — survives reboot |
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The startup-sequence copies `ENVARC:` to `ENV:` at boot.
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---
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## References
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- NDK39: `dos/var.h`
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- ADCD 2.1: `GetVar`, `SetVar`, `DeleteVar`
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