initial check-in, version 0.5.0

src/stdio/popen.c

@@ -0,0 +1,43 @@
+#include "stdio_impl.h"
+
+FILE *popen(const char *cmd, const char *mode)
+{
+	int p[2];
+	int op;
+	pid_t pid;
+	FILE *f;
+	const char *modes = "rw", *mi = strchr(modes, *mode);
+
+	if (mi) {
+		op = mi-modes;
+	} else {
+		errno = EINVAL;
+		return 0;
+	}
+	
+	if (pipe(p)) return NULL;
+	f = fdopen(p[op], mode);
+	if (!f) {
+		close(p[0]);
+		close(p[1]);
+		return NULL;
+	}
+	
+	pid = fork();
+	switch (pid) {
+	case -1:
+		fclose(f);
+		close(p[0]);
+		close(p[1]);
+		return NULL;
+	case 0:
+		dup2(p[1-op], 1-op);
+		close(p[0]);
+		close(p[1]);
+		execl("/bin/sh", "sh", "-c", cmd, (char *)0);
+		_exit(127);
+	}
+	close(p[1-op]);
+	f->pipe_pid = pid;
+	return f;
+}