tonyb@daemon.UUCP (Tony Birnseth) (04/29/85)
Index: /usr/src/bin/csh/{sh.c,sh.hist.c,sh.lex.c}
Description:
The original problem was from the statement in the man page
regarding relative history events:
"A history reference may be given without an event
specification e.g. '!$'. In this case the reference
is to the previous command unless a previous history
reference occurred on the same line in which case this
form repeats the previous reference."
Current implementation does not function that way. Relative
history commands !{$,*,etc.} are always relative to the current
command line.
Repeat-By:
% echo foo
foo
% cat /etc/printcap > /dev/null
% !?foo?^ !$
echo /dev/null
/dev/null
Fix:
Current behavior:
The history reference is reset to the current event every
time a history character is encountered. This prevents
relative history characters from ever referencing anything
but the previous command line. It became obvious, that to
keep the aliasing mechanism functioning for substitution of
"current command line arguments", Berkeley chose an
implementation that forces the history to be relative to the
current command. e.g. 'alias echo "/bin/echo \!*"' would echo
its arguments. This is accomplished by pushing the history
onto the history list, increment the event number, set the
"last event" counter equal to the current event (which hasn't
happened yet), then expand any history within aliases. (yuk!)
Unfortunately, this breaks the relative nature of the history
characters. (wouldn't it have been simpler to have a modifier
that referenced the current line?)
Psuedo Code (for comprehension)
Old Version:
Get a line
parse into words
expand any ! or $
if( any ! )
set last event = current event
(relative referencing is ALWAYS
relative to current event.) BUG!
save the history
increment the current event. BUG!
if(error)
break (actually longjump)
expand aliasing
if( any ! in alias itself )
set last event=current event.
BUG!
(relative reference is
relative to next event, which
hasn't happened yet.)
(This effect must be maintained)
execute the command line
continue
Needed changes:
1) Initialize the last event before any parsing occurs so that relative
history references are truly relative if the history reference is
reset. (ie !?foo?^ !$)
2) Save the history, but do not increment the current event until after
the aliasing occurs. The current event is added to the history list.
This allows '^' substitution on errors.
3) Increment the current event after aliasing occurs or if errors
are encountered.
Scenario now looks like:
New version:
get a line
set last event = current event
parse into words
expand any ! or $
save history
if(error)
increment current event
break
expand aliases
if(any ! in alias itself)
expand it, maintain relativity by
setting the next event in the history
stack, but don't increment the event
counter.
execute the command line
increment event number.
continue
Relative history is now relative.
The aliasing behavior involving relative history is maintained.
The changes were to:
1) Move initialization of lastev from getexcl() in sh.lex.c to process()
in sh.c.
2) pass eventno + 1 as a parameter to enthist() from savehist() in
sh.hist.c instead of ++eventno.
3) increment eventno after alias expansion has occurred in process()
in sh.c, or if an error occurred during parsing.
Tony Birnseth
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===============================================================================
The Diffs:
Line numbers will differ.
================================================================================
RCS file: RCS/sh.c,v
Retrieving revision 1.2
diff -b -r1.2 sh.c
770a771,776
> * Initialize the last event here so that relative history
> * accesses (ie !$ !*) remain relative.
> */
> lastev = eventno;
>
> /*
801c807,813
< error(err);
---
> /*
> * It would be nice if we could bury eventno++ in
> * error().
> * To many "uninteresting events" use error() to
> * jump back here.
> */
> eventno++, error(err);
808c820
< reset();
---
> eventno++, reset();
817c829,839
< error(err);
---
> eventno++, error(err);
>
> /*
> * Increment the acutal event number here.
> * If we waited till after execute(), interupted commands
> * would not get their history counter incremented.
> * We pad the eventno when savehist() above calls enthist()
> * to place the current command in the history list.
> */
> if ( t && intty && !whyles )
> eventno++;
===================================================================
RCS file: RCS/sh.hist.c,v
Retrieving revision 1.2
diff -b -r1.2 sh.hist.c
49c49
< enthist(++eventno, sp, 1);
---
> enthist(eventno + 1, sp, 1);
===================================================================
RCS file: RCS/sh.lex.c,v
Retrieving revision 1.1
diff -b -r1.1 sh.lex.c
474c474
< lastev = eventno;
---
> /* lastev = eventno; removed from here and done in process() in sh.c */