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)

1 files changed, 24 insertions, 0 deletions

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;
+}