[htdig] exit Commands in Sub-Shells

[Douglas K. <kl...@he...>]

Throughout the configure script for htdig-3.2.0b6 (and others too) are exit
commands run in sub-shells.  Some are in expressions like


if { (eval echo "$as_me:$LINENO: \"$ac_link_default\"") >&5
  (eval $ac_link_default) 2>&5
  ac_status=$?
  echo "$as_me:$LINENO: \$? = $ac_status" >&5
  (exit $ac_status); }; then


or precede an AND or an OR.  My interpretation is that these exit lines are
intended to produce logical values which will decide whether if conditions or
the first parts of AND's or OR's are fulfilled and are run in sub-shells to
avoid terminating the shell.


What role do the exit commands run in sub-shells play in expressions like


{ (eval echo "$as_me:$LINENO: \"$ac_compiler --version </dev/null >&5\"") >&5
  (eval $ac_compiler --version </dev/null >&5) 2>&5
  ac_status=$?
  echo "$as_me:$LINENO: \$? = $ac_status" >&5
  (exit $ac_status); }
{ (eval echo "$as_me:$LINENO: \"$ac_compiler -v </dev/null >&5\"") >&5
  (eval $ac_compiler -v </dev/null >&5) 2>&5
  ac_status=$?
  echo "$as_me:$LINENO: \$? = $ac_status" >&5
  (exit $ac_status); }
{ (eval echo "$as_me:$LINENO: \"$ac_compiler -V </dev/null >&5\"") >&5
  (eval $ac_compiler -V </dev/null >&5) 2>&5
  ac_status=$?
  echo "$as_me:$LINENO: \$? = $ac_status" >&5
  (exit $ac_status); }


where they aren't followed by a condition evaluation?


What purpose does a command like


{ (exit 1); exit 1; }; }


serve?  Why the sub-shell with the second exit and why the braces?

Douglas


========
Douglas Kline
kl...@he...