1 files changed, 28 insertions, 0 deletions
diff --git a/usr/head.c b/usr/head.c
new file mode 100644
index 0000000..3298e54
--- /dev/null
+++ b/usr/head.c
@@ -0,0 +1,28 @@
+#include "gbos.h"
+/* head [-n N] [N] [file]: first N lines of a file or stdin (default 10). */
+void main(void) {
+    char *argv[8];
+    unsigned char argc = argv_parse(argv, 8);
+    char *nv = optval(argv, argc, 'n');
+    unsigned char n = 10, lines = 0, i, fd = NOFD;
+    char *fname = 0;
+    int ch;
+    if (nv) n = atou(nv);
+    for (i = 0; i < argc; i++) {
+        if (argv[i][0] == '-') continue;
+        if (nv == argv[i]) continue;
+        if (!nv && argv[i][0] >= '0' && argv[i][0] <= '9') { n = atou(argv[i]); continue; }
+        fname = argv[i]; break;
+    }
+    if (fname) {
+        fd = open(fname, O_READ);
+        if (fd > 3) { puts("head: no such file"); nl(); return; }
+    }
+    for (;;) {
+        if (fd > 3) { char c = readc(); if (c == EOF) break; ch = c; }
+        else { ch = fgetc(fd); if (ch < 0) break; }
+        if (lines < n) putc((char)ch);
+        if (ch == '\n') lines++;
+    }
+    if (fd != NOFD) close(fd);
+}