Re: fc command substitution behavior, possible bug

[Chet Ramey]

smallnow wrote:
> $ echo $BASH_VERSION
> 3.2.48(1)-release
> $ echo $(fc -nl -1)
> echo $BASH_VERSION
> 
> 
> $ echo $BASH_VERSION
> 4.0.10(2)-release
> $ echo $(fc -nl -1)
> echo $(fc -nl -1)
> 
> I see there were a lot of changes to fc, is this intended or a bug?

The off-by-one errors that occurred when running fc in non-interactive
contexts were fixed, but it's possible that the changes were too
aggressive.  There's no reason that `echo $(fc -nl -1)' and `fc -nl -1'
shouldn't echo the same thing when run from the same shell -- command
substitution should inherit the history settings and history list.

See if the following patch fixes things for you.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer

Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/

*** ../bash-4.0-patched/builtins/fc.def 2009-01-04 14:32:22.000000000 -0500
--- builtins/fc.def     2009-03-21 14:03:43.000000000 -0400
***************
*** 89,92 ****
--- 89,93 ----
  extern int literal_history;
  extern int posixly_correct;
+ extern int subshell_environment, interactive_shell;
  
  extern int unlink __P((const char *));
***************
*** 173,177 ****
    register char *sep;
    int numbering, reverse, listing, execute;
!   int histbeg, histend, last_hist, retval, opt;
    FILE *stream;
    REPL *rlist, *rl;
--- 174,178 ----
    register char *sep;
    int numbering, reverse, listing, execute;
!   int histbeg, histend, last_hist, retval, opt, rh;
    FILE *stream;
    REPL *rlist, *rl;
***************
*** 276,279 ****
--- 277,282 ----
        fprintf (stderr, "%s\n", command);
        fc_replhist (command);  /* replace `fc -s' with command */
+       /* Posix says that the re-executed commands should be entered into the
+        history. */
        return (parse_and_execute (command, "fc", SEVAL_NOHIST));
      }
***************
*** 294,298 ****
       so we check hist_last_line_added. */
  
!   last_hist = i - remember_on_history - hist_last_line_added;
  
    if (list)
--- 297,306 ----
       so we check hist_last_line_added. */
  
!   /* Even though command substitution through parse_and_execute turns off
!      remember_on_history, command substitution in a shell when set -o history
!      has been enabled (interactive or not) should use it in the last_hist
!      calculation as if it were on. */
!   rh = remember_on_history || ((subshell_environment & SUBSHELL_COMSUB) && 
enable_history_list);
!   last_hist = i - rh - hist_last_line_added;
  
    if (list)
***************
*** 457,461 ****
       HIST_ENTRY **hlist;
  {
!   int sign, n, clen;
    register int i, j;
    register char *s;
--- 465,469 ----
       HIST_ENTRY **hlist;
  {
!   int sign, n, clen, rh;
    register int i, j;
    register char *s;
***************
*** 473,477 ****
       so we check hist_last_line_added.  This needs to agree with the
       calculation of last_hist in fc_builtin above. */
!   i -= remember_on_history + hist_last_line_added;
  
    /* No specification defaults to most recent command. */
--- 481,490 ----
       so we check hist_last_line_added.  This needs to agree with the
       calculation of last_hist in fc_builtin above. */
!   /* Even though command substitution through parse_and_execute turns off
!      remember_on_history, command substitution in a shell when set -o history
!      has been enabled (interactive or not) should use it in the last_hist
!      calculation as if it were on. */
!   rh = remember_on_history || ((subshell_environment & SUBSHELL_COMSUB) && 
enable_history_list);
!   i -= rh + hist_last_line_added;
  
    /* No specification defaults to most recent command. */