libc + CLI tools: a small C userland

- libc: add putc, puts, strlen, getargs (args string), EOF (=4) for readc.
- args: shell splits the command line at the first space ("cmd\0args\0" at
  $A000, inherited by the child via fork); getargs() returns the arg string.
- shell: exit on Ctrl-D/EOF; $ prompt over a clean read loop.
- tools (c/): echo (argv), cat (stdin->stdout to EOF), uname, pid (decimal
  print), true, false. Each built to a ROM-bank blob and registered.
- Makefile: CBLOBS list builds all C programs.
- README: document libc + the tool set.

1 files changed, 11 insertions, 5 deletions

diff --git a/c/gbos.h b/c/gbos.h
index 9a09a5d..3a10e06 100644
--- a/c/gbos.h
+++ b/c/gbos.h
@@ -1,9 +1,15 @@
-/* gbos userland C API (thin wrappers over rst $30 syscalls; see c/libc.asm) */
+/* gbos userland C API (thin wrappers over rst $30 syscalls; see c/libc.s) */
 #ifndef GBOS_H
 #define GBOS_H
-void          writes(const char *buf, unsigned char len); /* write to console */
-void          nl(void);                                   /* newline (CRLF)   */
-unsigned char readc(void);                                /* read one byte    */
-void          sexit(unsigned char code);                  /* exit(code)       */
+#define EOF 4                 /* readc() returns this at end of input */
+
+void          writes(const char *buf, unsigned char len);
+void          putc(char c);
+void          puts(const char *s);        /* write a NUL-terminated string */
+void          nl(void);                   /* newline (CRLF)                */
+unsigned char strlen(const char *s);
+char         *getargs(void);              /* this program's argument string */
+char          readc(void);                /* one input byte, EOF at end    */
+void          sexit(unsigned char code);
 unsigned char getpid(void);
 #endif