Here's a silly ed(1) session:
$ ed -p ":> "
:> P
P
*q
$
Notice how the prompt string changed from the custom prompt ":> " to
the default prompt "*".
This behavior seems to contradict both the man page and POSIX:
>From ed(1):
-p string Specifies a command prompt. This may be toggled on and off
with the P command.
>From POSIX:
The P command shall cause ed to prompt with an <asterisk> ('*') (or
string, if -p is specified) for all subsequent commands. The P command
alternatively shall turn this mode on and off; it shall be initially on
if the -p option is specified; otherwise, off.
With the patch below, the above session becomes
$ ed -p ":> "
:> P
P
:> q
$
which, I believe, is closer to both the documentation and POSIX.
This also matches the behavior of GNU Ed 1.10.
Index: bin/ed/main.c
===================================================================
RCS file: /cvs/src/bin/ed/main.c,v
retrieving revision 1.43
diff -u -p -r1.43 main.c
--- bin/ed/main.c 16 Jan 2015 06:39:32 -0000 1.43
+++ bin/ed/main.c 18 Jun 2015 10:33:21 -0000
@@ -110,7 +110,7 @@ top:
while ((c = getopt(argc, argv, "p:sx")) != -1)
switch (c) {
case 'p': /* set prompt */
- prompt = optarg;
+ dps = prompt = optarg;
break;
case 's': /* run script */
scripted = 1;
