On 12/9/2017 1:28 PM, Bryan Steele wrote:
> On Sat, Dec 09, 2017 at 06:44:44PM +0100, Theo Buehler wrote:
>> This was discussed in a smaller circle and has been in snaps for two
>> days, but I'd like to show this to a wider audience.
>>
>> Theo asked me to make sure that all our shells print a prompt including
>> the hostname by default. The reasoning is roughly as follows:
>>
>> With tmux, ssh and vmd, we tend to open shells on many different hosts
>> simultaneously and the default prompts '$ ' and '# ' for {,k}sh as well
>> as '% ' and '# ' for csh become dangerous: it's very easy to issue a
>> command on the wrong host.
>>
>> This can easily be avoided by displaying the hostname in the prompt.
>> Everything beyond "hostname{$,#,%} " is going to be a matter of taste,
>> so we left it at that. If you use an FQDN, only the first part (the
>> output of 'hostname -s') will be printed.
>>
>> Since not everybody makes use of the config files in /etc/skel or runs
>> only login shells, it is not really possible to handle this with config
>> files. Thus, we decided to hardcode it in the shells. We are aware that
>> POSIX says that PS1 defaults to '$ ' or '# ' for sh(1).
>>
>> The simplest case is ksh: rely on the already existing shell escapes.
>> For sh we can easily fall back to these (the diff to ksh/lex.c). For
>> csh, I decided to implement the "%m" prompt escape which is standard in
>> c-type shells, so I don't expect this to cause surprises.
>>
>> In single user mode and the early installer, gethostname() returns the
>> empty string, so the familiar prompts will be displayed there.
> I think we should go ahead with this for the reasons mentioned, the
> default configuration should make things easier for the people using it,
> which means developers doing release builds, spinning up vms, etc.
>
> People can go on and on about standards compliance, but if it means
> someone is less likely to reboot the wrong machine, or worse, then
> POSIX be damned.
>
> ok brynet@
I'm with brynet@ and the others on this. Was a nice surprise when I
installed a new snap last night, already proved itself to be useful.
ok bcallah@, fwiw
>> Index: bin/csh/const.c
>> ===================================================================
>> RCS file: /var/cvs/src/bin/csh/const.c,v
>> retrieving revision 1.8
>> diff -u -p -r1.8 const.c
>> --- bin/csh/const.c 26 Oct 2015 16:27:04 -0000 1.8
>> +++ bin/csh/const.c 8 Dec 2017 12:15:26 -0000
>> @@ -114,6 +114,8 @@ Char STRprintexitvalue[] = { 'p', 'r', '
>> 'a', 'l', 'u', 'e', '\0' };
>> Char STRprompt[] = { 'p', 'r', 'o', 'm', 'p', 't', '\0' };
>> Char STRprompt2[] = { 'p', 'r', 'o', 'm', 'p', 't', '2', '\0' };
>> +Char STRpromptroot[] = { '%', 'm', '#', ' ', '\0' };
>> +Char STRpromptuser[] = { '%', 'm', '%', ' ', '\0' };
>> Char STRpushdsilent[] = { 'p', 'u', 's', 'h', 'd', 's', 'i', 'l',
>> 'e', 'n',
>> 't', '\0' };
>> Char STRret[] = { '\n', '\0' };
>> @@ -138,8 +140,6 @@ Char STRspor2sp[] = { ' ', '|', '|', ' '
>> Char STRsporsp[] = { ' ', '|', ' ', '\0' };
>> Char STRstar[] = { '*', '\0' };
>> Char STRstatus[] = { 's', 't', 'a', 't', 'u', 's', '\0' };
>> -Char STRsymcent[] = { '%', ' ', '\0' };
>> -Char STRsymhash[] = { '#', ' ', '\0' };
>> Char STRterm[] = { 't', 'e', 'r', 'm', '\0' };
>> Char STRthen[] = { 't', 'h', 'e', 'n', '\0' };
>> Char STRtilde[] = { '~', '\0' };
>> Index: bin/csh/csh.c
>> ===================================================================
>> RCS file: /var/cvs/src/bin/csh/csh.c,v
>> retrieving revision 1.41
>> diff -u -p -r1.41 csh.c
>> --- bin/csh/csh.c 30 Aug 2017 06:42:21 -0000 1.41
>> +++ bin/csh/csh.c 8 Dec 2017 12:16:00 -0000
>> @@ -401,7 +401,7 @@ main(int argc, char *argv[])
>> * Set up the prompt.
>> */
>> if (prompt) {
>> - set(STRprompt, Strsave(uid == 0 ? STRsymhash : STRsymcent));
>> + set(STRprompt, Strsave(uid == 0 ? STRpromptroot : STRpromptuser));
>> /* that's a meta-questionmark */
>> set(STRprompt2, Strsave(STRmquestion));
>> }
>> @@ -1283,7 +1283,16 @@ printprompt(void)
>> for (cp = value(STRprompt); *cp; cp++)
>> if (*cp == HIST)
>> (void) fprintf(cshout, "%d", eventno + 1);
>> - else {
>> + else if (*cp == '%' && *(cp + 1) == 'm') {
>> + char hostname[HOST_NAME_MAX + 1];
>> + char *p;
>> +
>> + gethostname(hostname, sizeof hostname);
>> + if ((p = strchr(hostname, '.')) != NULL)
>> + *p = '\0';
>> + fprintf(cshout, "%s", hostname);
>> + cp++;
>> + } else {
>> if (*cp == '\\' && cp[1] == HIST)
>> cp++;
>> (void) vis_fputc(*cp | QUOTE, cshout);
>> Index: bin/ksh/lex.c
>> ===================================================================
>> RCS file: /var/cvs/src/bin/ksh/lex.c,v
>> retrieving revision 1.72
>> diff -u -p -r1.72 lex.c
>> --- bin/ksh/lex.c 7 Dec 2017 01:54:33 -0000 1.72
>> +++ bin/ksh/lex.c 8 Dec 2017 11:02:10 -0000
>> @@ -1246,7 +1246,8 @@ dopprompt(const char *sp, int ntruncate,
>> cp++;
>> if (!*cp)
>> break;
>> - if (Flag(FSH))
>> + /* Expand \h and \$ for both, sh(1) and ksh(1) */
>> + if (Flag(FSH) && !(*cp == 'h' || *cp == 'p'))
>> snprintf(strbuf, sizeof strbuf, "\\%c", *cp);
>> else switch (*cp) {
>> case 'a': /* '\' 'a' bell */
>> Index: bin/ksh/main.c
>> ===================================================================
>> RCS file: /var/cvs/src/bin/ksh/main.c,v
>> retrieving revision 1.84
>> diff -u -p -r1.84 main.c
>> --- bin/ksh/main.c 7 Dec 2017 01:54:33 -0000 1.84
>> +++ bin/ksh/main.c 8 Dec 2017 10:26:35 -0000
>> @@ -316,7 +316,7 @@ main(int argc, char *argv[])
>> /* Set PS1 if it isn't set */
>> if (!(vp->flag & ISSET)) {
>> /* setstr can't fail here */
>> - setstr(vp, safe_prompt, KSH_RETURN_ERROR);
>> + setstr(vp, "\\h\\$ ", KSH_RETURN_ERROR);
>> }
>> }
>>
>>
>>
