Thanks to John Cummings.

src/cmd/upas/send/translate.c

@@ -0,0 +1,43 @@
+#include "common.h"
+#include "send.h"
+
+/* pipe an address through a command to translate it */
+extern dest *
+translate(dest *dp)
+{
+	process *pp;
+	String *line;
+	dest *rv;
+	char *cp;
+	int n;
+
+	pp = proc_start(s_to_c(dp->repl1), (stream *)0, outstream(), outstream(), 1, 0);
+	if (pp == 0) {
+		dp->status = d_resource;
+		return 0;
+	}
+	line = s_new();
+	for(;;) {
+		cp = Brdline(pp->std[1]->fp, '\n');
+		if(cp == 0)
+			break;
+		if(strncmp(cp, "_nosummary_", 11) == 0){
+			nosummary = 1;
+			continue;
+		}
+		n = Blinelen(pp->std[1]->fp);
+		cp[n-1] = ' ';
+		s_nappend(line, cp, n);
+	}
+	rv = s_to_dest(s_restart(line), dp);
+	s_restart(line);
+	while(s_read_line(pp->std[2]->fp, line))
+		;
+	if ((dp->pstat = proc_wait(pp)) != 0) {
+		dp->repl2 = line;
+		rv = 0;
+	} else
+		s_free(line);
+	proc_free(pp);
+	return rv;
+}