shell: I/O redirection (>/<) and pipes (|); rewrite shell in C

- kernel I/O routing: PCB gains PROC_STDIN/PROC_STDOUT (default console $FF),
  inherited across fork. KGetc/KPutc route read/write/putc to the console or a
  file fd. New syscalls: putc(16), setin(17), setout(18), lookup(19).
  read/write now go through the routing; putc/puts/nl use SYS_PUTC.
- sys_lookup + NameTable move command-name resolution into the kernel.
- shell rewritten in C (c/sh.c): tokenizes a line, parses > / < / |, and drives
  fork+setin/setout+exec+wait. Pipes run as 'a > __pipe ; b < __pipe' (temp
  file). asm shell + cmdtab removed; StrEqual/SkipName kept for sys_lookup.
- libc: fork/exec/wait/setin/setout/lookup wrappers.
- verified: echo>file, cat file, wc<file, cat readme|wc -l, echo ...|wc.

1 files changed, 8 insertions, 0 deletions

diff --git a/c/gbos.h b/c/gbos.h
index d8c8eb3..fa926fd 100644
--- a/c/gbos.h
+++ b/c/gbos.h
@@ -30,4 +30,12 @@ void          fremove(const char *name);
 #define O_READ  0
 #define O_WRITE 1
 #define NOFD    0xFF
+
+/* process control (c/libc.s) */
+unsigned char fork(void);
+void          exec(unsigned char id);       /* replace image; never returns */
+unsigned char wait(void);
+void          setin(unsigned char fd);      /* redirect stdin  ($FF=console) */
+void          setout(unsigned char fd);     /* redirect stdout ($FF=console) */
+unsigned char lookup(const char *name);     /* command name -> program id    */
 #endif