usr: grep, more, cp, nc - and make pollcon pump the link

The shell has had pipes for a while with nothing to pipe *through*, and
an 18-row screen with no way to stop output scrolling off it.

- grep [-vin] PAT [file]: substring match (no regex), stdin or a file,
  grep(1)'s exit convention. The other end of the pipe, at last.
- more [file]: pages 17 lines at a time, --More-- bar in white-on-blue,
  any key pages, q quits. Counts *screen* rows, so wrapped lines pay
  their real cost. Keys come from pollin/pollcon, not stdin, so
  `cat big | more` still has a keyboard.
- cp SRC DST: the fs has rm/mkdir but no way to duplicate a file. mv is
  this plus rm (there is no rename). Rejects SRC == DST, which would
  otherwise truncate the source via O_WRITE before reading a byte.
- nc [-s] HOST PORT: raw TCP. Interactive (START sends the line with a
  CRLF, /q quits) or -s to pump stdin and print the reply with its own
  wall-clock idle timeout, because the kernel's blocking recv counts
  pumps, not seconds. Generalizes what chat/irc hardcode:
  `nc towel.blinkenlights.nl 23` works.

sys_pollcon now pumps the link before draining the console ring. The
ring is filled *by* net_pump, so a program that never touches the
network polled a ring nothing would ever fill: host-injected keys
(gbtype/gbdemo) hung `more` forever, and the Game Boy stopped answering
pings for as long as it ran. KGetc already pumps for this reason.

New tools take banks 35-38. Locals over statics in all four: a program's
_DATA starts at $A000, where the shell leaves the command line.

1 files changed, 62 insertions, 0 deletions

diff --git a/usr/cp.c b/usr/cp.c
new file mode 100644
index 0000000..61a1e0b
--- /dev/null
+++ b/usr/cp.c
@@ -0,0 +1,62 @@
+#include "gbos.h"
+/* cp SRC DST: copy a file. There is no rename syscall, so `mv` is this plus
+ * rm - and O_WRITE truncates (see fs.asm sys_open .trunc), which is exactly
+ * why the SRC == DST case below has to be rejected before opening DST. */
+
+static unsigned char streq(const char *a, const char *b) {
+    while (*a && *a == *b) {
+        a++;
+        b++;
+    }
+    return (unsigned char)(*a == *b);
+}
+
+void main(void) {
+    char *argv[4];
+    unsigned char argc = argv_parse(argv, 4);
+    unsigned char in, out;
+    int ch;
+
+    if (argc < 2) {
+        puts("usage: cp SRC DST");
+        nl();
+        sexit(2);
+    }
+    if (streq(argv[0], argv[1])) {
+        puts("cp: SRC and DST are the same file");
+        nl();
+        sexit(2);
+    }
+
+    in = open(argv[0], O_READ);
+    if (in == EISDIR) {
+        puts("cp: SRC is a directory");
+        nl();
+        sexit(2);
+    }
+    if (in == NOFD) {
+        puts("cp: no such file: ");
+        puts(argv[0]);
+        nl();
+        sexit(2);
+    }
+
+    out = open(argv[1], O_WRITE); /* creates, or truncates an existing file */
+    if (out == EISDIR) {
+        puts("cp: DST is a directory");
+        nl();
+        close(in);
+        sexit(2);
+    }
+    if (out == NOFD) {
+        puts("cp: cannot create ");
+        puts(argv[1]);
+        nl();
+        close(in);
+        sexit(2); /* out of inodes/blocks, or a bad path */
+    }
+
+    while ((ch = fgetc(in)) >= 0) fputc(out, (char)ch);
+    close(in);
+    close(out); /* flushes the inode */
+}