libc: option parsing (hasflag/optval); wc -l/-w/-c, head -n N

- hasflag(argv,argc,f): single-char flag present (-f or within -abc)
- optval(argv,argc,opt): value for -opt (-n 5 or -n5)
- wc supports -l/-w/-c (default all); head supports -n N (and bare N)

4 files changed, 47 insertions, 15 deletions

diff --git a/c/gbos.h b/c/gbos.h
index cf94128..47f75ad 100644
--- a/c/gbos.h
+++ b/c/gbos.h
@@ -17,4 +17,6 @@ unsigned char getpid(void);
 void          putu(unsigned int n);              /* print decimal          */
 unsigned char atou(const char *s);               /* parse decimal          */
 unsigned char argv_parse(char **argv, unsigned char maxv); /* argc/argv     */
+unsigned char hasflag(char **argv, unsigned char argc, char f);   /* -x flag  */
+char         *optval(char **argv, unsigned char argc, char opt);  /* -x VALUE */
 #endif
diff --git a/c/head.c b/c/head.c
index 9363b1c..952d4c5 100644
--- a/c/head.c
+++ b/c/head.c
@@ -1,12 +1,13 @@
 #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. */
+/* head [-n N] [N]: print the first N lines of stdin (default 10). */
 void main(void) {
-    char *a = getargs();
-    unsigned char n = 10;
-    unsigned char lines = 0;
+    char *argv[8];
+    unsigned char argc = argv_parse(argv, 8);
+    char *nv = optval(argv, argc, 'n');
+    unsigned char n = 10, lines = 0;
     char c;
-    if (*a) n = atou(a);
+    if (nv) n = atou(nv);
+    else if (argc > 0 && argv[0][0] >= '0' && argv[0][0] <= '9') n = atou(argv[0]);
     for (;;) {
         c = readc();
         if (c == EOF) break;
diff --git a/c/libc.c b/c/libc.c
index 3b9883b..9da63bc 100644
--- a/c/libc.c
+++ b/c/libc.c
@@ -32,3 +32,27 @@ unsigned char argv_parse(char **argv, unsigned char maxv) {
     }
     return argc;
 }
+
+/* return nonzero if single-char flag `f` appears (as -f or within -abc) */
+unsigned char hasflag(char **argv, unsigned char argc, char f) {
+    unsigned char i, j;
+    for (i = 0; i < argc; i++) {
+        if (argv[i][0] != '-') continue;
+        for (j = 1; argv[i][j]; j++)
+            if (argv[i][j] == f) return 1;
+    }
+    return 0;
+}
+
+/* return the value for option -<opt> ("-n 5" or "-n5"), or 0 if absent */
+char *optval(char **argv, unsigned char argc, char opt) {
+    unsigned char i;
+    for (i = 0; i < argc; i++) {
+        if (argv[i][0] == '-' && argv[i][1] == opt) {
+            if (argv[i][2]) return &argv[i][2];
+            if (i + 1 < argc) return argv[i+1];
+            return 0;
+        }
+    }
+    return 0;
+}
diff --git a/c/wc.c b/c/wc.c
index a957542..86c3aed 100644
--- a/c/wc.c
+++ b/c/wc.c
@@ -1,20 +1,25 @@
 #include "gbos.h"
-/* wc: count lines, words, chars of stdin (like `wc`). */
+/* wc [-l] [-w] [-c]: count lines, words, chars of stdin (default: all). */
 void main(void) {
+    char *argv[8];
+    unsigned char argc = argv_parse(argv, 8);
+    unsigned char wl = hasflag(argv, argc, 'l');
+    unsigned char ww = hasflag(argv, argc, 'w');
+    unsigned char wch = hasflag(argv, argc, 'c');
     unsigned int lines = 0, words = 0, chars = 0;
-    unsigned char inword = 0;
+    unsigned char inword = 0, first = 1;
     char c;
+    if (!wl && !ww && !wch) { wl = ww = wch = 1; }
     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++;
-        }
+        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();
+    if (wl)  { putu(lines); first = 0; }
+    if (ww)  { if (!first) putc(' '); putu(words); first = 0; }
+    if (wch) { if (!first) putc(' '); putu(chars); }
+    nl();
 }