tools: wc, head, and an argc/argv demo (args) + libc.c helpers

- c/libc.c: shared C helpers linked into every program - putu (print decimal),
  atou (parse decimal), argv_parse (tokenize getargs() into argc/argv).
- wc: count lines/words/chars of stdin. head [n]: first n lines (drains rest to
  EOF). args: argc/argv demo.
- pid now uses libc putu; build.sh links libc.c; Makefile CBLOBS + libc dep.
- README: document the new tools + argv_parse.
- verified: 'args one two three' -> argc=3/argv[..]; wc '2 3 16'; head 2.

1 files changed, 16 insertions, 0 deletions

diff --git a/c/head.c b/c/head.c
new file mode 100644
index 0000000..9363b1c
--- /dev/null
+++ b/c/head.c
@@ -0,0 +1,16 @@
+#include "gbos.h"
+/* head [n]: print the first n lines of stdin (default 10). Drains the rest to
+   EOF so the shell sees a clean end of input. */
+void main(void) {
+    char *a = getargs();
+    unsigned char n = 10;
+    unsigned char lines = 0;
+    char c;
+    if (*a) n = atou(a);
+    for (;;) {
+        c = readc();
+        if (c == EOF) break;
+        if (lines < n) putc(c);
+        if (c == '\n') lines++;
+    }
+}