ed: add support for -p command-line option as mandated by POSIX

The POSIX.1-2008 specification of ed(1) mandates two command-line
options: -p (for specifying a prompt string) and -s (to suppress writing
of byte counts). This commit adds support for the former. Furthermore,
it also changes the default prompt string to an empty string (instead
of ": ") since this is also mandated by POSIX:

	-p string Use string as the prompt string when in command mode.
	          By default, there shall be no prompt string.

function                                             old     new   delta
ed_main                                              112     144     +32
packed_usage                                       34074   34097     +23
doCommands                                          1889    1887      -2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 55/-2)              Total: 53 bytes

Signed-off-by: Sören Tempel <soeren+git@soeren-tempel.net>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/editors/ed.c b/editors/ed.c
index 14540e566..18faba5a4 100644
--- a/editors/ed.c
+++ b/editors/ed.c
@@ -18,7 +18,7 @@
 
 //applet:IF_ED(APPLET(ed, BB_DIR_BIN, BB_SUID_DROP))
 
-//usage:#define ed_trivial_usage "[FILE]"
+//usage:#define ed_trivial_usage "[-p PROMPT] [FILE]"
 //usage:#define ed_full_usage ""
 
 #include "libbb.h"
@@ -48,6 +48,7 @@ struct globals {
         char *bufBase;
         char *bufPtr;
         char *fileName;
+        const char *prompt;
         LINE lines;
         smallint dirty;
         int marks[26];
@@ -57,6 +58,7 @@ struct globals {
 #define bufBase            (G.bufBase           )
 #define bufPtr             (G.bufPtr            )
 #define fileName           (G.fileName          )
+#define prompt             (G.prompt            )
 #define curNum             (G.curNum            )
 #define lastNum            (G.lastNum           )
 #define bufUsed            (G.bufUsed           )
@@ -793,7 +795,7 @@ static void doCommands(void)
                  * 0  on ctrl-C,
                  * >0 length of input string, including terminating '\n'
                  */
-                len = read_line_input(NULL, ": ", buf, sizeof(buf));
+                len = read_line_input(NULL, prompt, buf, sizeof(buf));
                 if (len <= 0)
                         return;
                 while (len && isspace(buf[--len]))
@@ -1005,8 +1007,12 @@ int ed_main(int argc UNUSED_PARAM, char **argv)
         lines.next = &lines;
         lines.prev = &lines;
 
-        if (argv[1]) {
-                fileName = xstrdup(argv[1]);
+        prompt = ""; /* no prompt by default */
+        getopt32(argv, "p:", &prompt);
+        argv += optind;
+
+        if (argv[0]) {
+                fileName = xstrdup(argv[0]);
                 if (!readLines(fileName, 1)) {
                         return EXIT_SUCCESS;
                 }