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, 20 insertions, 0 deletions

diff --git a/c/wc.c b/c/wc.c
new file mode 100644
index 0000000..a957542
--- /dev/null
+++ b/c/wc.c
@@ -0,0 +1,20 @@
+#include "gbos.h"
+/* wc: count lines, words, chars of stdin (like `wc`). */
+void main(void) {
+    unsigned int lines = 0, words = 0, chars = 0;
+    unsigned char inword = 0;
+    char c;
+    for (;;) {
+        c = readc();
+        if (c == EOF) break;
+        chars++;
+        if (c == '\n') lines++;
+        if (c == ' ' || c == '\n' || c == '\r' || c == '\t') {
+            inword = 0;
+        } else if (!inword) {
+            inword = 1;
+            words++;
+        }
+    }
+    putu(lines); putc(' '); putu(words); putc(' '); putu(chars); nl();
+}