diff options
Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 37 |
1 files changed, 25 insertions, 12 deletions
@@ -58,22 +58,33 @@ across a syscall (`push hl` / `pop hl`). Libc syscall stubs handle this for C. | 2 | read | ✅ blocking console input (1 byte) via external-clock serial | | 4,5,9,10 | open/close/kill/brk | ⛔ `ENOSYS` | -### The shell (PROG_SH) +### The shell (`c/sh.c`) -init `exec`s a tiny shell: **prompt → read a line (with echo) → match a command -→ `fork`+`exec`+`wait`**. Commands live in a table (`worker`, `hello`). Runs -entirely over the headless serial console: +init `exec`s the shell (written in C). It reads a line, tokenizes it, and runs +commands with **I/O redirection and pipes**: ``` -$ hello -hello world! -$ worker -worker! -$ foo -? -$ +$ echo hello > note # redirect stdout to a file +$ cat note +hello +$ wc < note # redirect stdin from a file +1 1 6 +$ cat readme | wc -l # pipe (via a temp file) +2 +$ echo one two three | wc +1 3 14 ``` +Operators must be space-separated (`cat readme > out`). Command names are +resolved by the kernel (`sys_lookup` + `NameTable`). + +**How I/O routing works.** Each process has a `stdin`/`stdout` fd in its PCB +(default `$FF` = console). `read`/`write`/`putc` route through the kernel +(`KGetc`/`KPutc`): console when the fd is `$FF`, otherwise the filesystem +(`getb`/`putb`). The shell forks a child, the child `setin`/`setout`s to open +files, then `exec`s — so the program's I/O lands in the file. A pipe +`a | b` is run as `a > __pipe ; b < __pipe ; rm __pipe`. + ### Process lifecycle (exit / wait / reaping) The classic Unix zombie/reap dance, adapted to banked memory: @@ -295,7 +306,9 @@ $ rm notes - [x] `wc`, `head`, and an `argc/argv` demo (`args`) + `argv_parse` in libc - [x] option parsing (`hasflag`/`optval`): `wc -l/-w/-c`, `head -n N` - [x] a RAM filesystem (WRAMX) + `ls`/`cat`/`save`/`rm`; `wc`/`head` read files -- [ ] more tools (`rev`, `grep`, `tail`), shell redirection (`>`/`|`) +- [x] shell in C with redirection (`>`/`<`) and pipes (`|`, via a temp file) +- [x] per-process stdin/stdout routing (`KGetc`/`KPutc`, `setin`/`setout`) +- [ ] more tools (`rev`, `grep`, `tail`), true concurrent pipes - [ ] battery-backed files (move the FS to cart SRAM), directories - [ ] Preemptive scheduling: real context save in `TimerISR` → `hSwitchTo` - [ ] Use the `$D000-$DFFF` u-area (SVBK) for per-process kernel state / kstack |