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#include "gbos.h"
/* gbos shell: prompt -> read a line -> parse -> run, with I/O redirection
( > file, < file ) and pipes ( cmd1 | cmd2, via a temp file ).
Operators must be space-separated (e.g. cat readme > out ). */
#define ARGV0 ((char *)0xA000) /* where a child reads its command line */
/* split s into space-separated tokens (NUL-terminated in place). */
static unsigned char tokenize(char *s, char **tok, unsigned char max) {
unsigned char n = 0;
for (;;) {
while (*s == ' ') *s++ = 0;
if (*s == 0) break;
if (n < max) tok[n++] = s;
while (*s && *s != ' ') s++;
}
return n;
}
static unsigned char isop(char *t, char c) { return t[0] == c && t[1] == 0; }
/* build the child command line "name\0arg1 arg2\0" at 0xA000 */
static void set_cmdline(char **tok, unsigned char start, unsigned char end) {
char *p = ARGV0, *t;
unsigned char i;
t = tok[start];
while (*t) *p++ = *t++;
*p++ = 0; /* NUL after the command word */
for (i = start + 1; i < end; i++) {
if (i > start + 1) *p++ = ' ';
t = tok[i];
while (*t) *p++ = *t++;
}
*p = 0;
}
/* run tok[start..end): parse its own >/< redirects, honor forced in/out. */
static void run(char **tok, unsigned char start, unsigned char end,
unsigned char infd, unsigned char outfd) {
unsigned char i, cmdend = end, myin = NOFD, myout = NOFD, id, pid;
for (i = start; i < end; i++) {
if (isop(tok[i], '>')) {
if (i + 1 < end) myout = open(tok[i + 1], O_WRITE);
if (i < cmdend) cmdend = i;
} else if (isop(tok[i], '<')) {
if (i + 1 < end) myin = open(tok[i + 1], O_READ);
if (i < cmdend) cmdend = i;
}
}
id = lookup(tok[start]);
if (id == NOFD) { puts(tok[start]); puts(": not found"); nl(); goto done; }
set_cmdline(tok, start, cmdend);
pid = fork();
if (pid == 0) {
if (myin != NOFD) setin(myin);
else if (infd != NOFD) setin(infd);
if (myout != NOFD) setout(myout);
else if (outfd != NOFD) setout(outfd);
exec(id);
}
wait();
done:
if (myin != NOFD) close(myin);
if (myout != NOFD) close(myout);
}
void main(void) {
char line[80];
char *tok[16];
for (;;) {
unsigned char nt, i, pipepos, c;
puts("$ ");
/* read a line (echoing), stop at newline; exit on EOF */
i = 0;
for (;;) {
c = readc();
if (c == EOF) return;
if (c == '\r' || c == '\n') { nl(); break; }
if (i < 79) { line[i++] = c; putc(c); }
}
line[i] = 0;
nt = tokenize(line, tok, 16);
if (nt == 0) continue;
pipepos = 0;
for (i = 1; i < nt; i++)
if (isop(tok[i], '|')) { pipepos = i; break; }
if (pipepos) {
unsigned char pw = open("__pipe", O_WRITE);
run(tok, 0, pipepos, NOFD, pw);
close(pw);
{ unsigned char pr = open("__pipe", O_READ);
run(tok, pipepos + 1, nt, pr, NOFD);
close(pr); }
fremove("__pipe");
} else {
run(tok, 0, nt, NOFD, NOFD);
}
}
}
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