#serial 4# AC_PROG_SHELL# -------------# Check for a working (i.e. POSIX-compatible) shell.# Written by Paul Eggert <eggert@twinsun.com>,# from an idea suggested by Albert Chin-A-Young <china@thewrittenword.com>.AC_DEFUN([AC_PROG_SHELL],  [AC_MSG_CHECKING([for a POSIX-compliant shell])   AC_CACHE_VAL(ac_cv_path_shell,     [ac_command='	# Test the noclobber option, using the portable POSIX.2 syntax.	set -C	rm -f conftest.c	>conftest.c || exit	>|conftest.c || exit	!>conftest.c || exit      '      ac_cv_path_shell=no      case $SHELL in      /*)	rm -f conftest.c	if ("$SHELL" -c "$ac_command") 2>/dev/null; then	  ac_cv_path_shell=$SHELL	fi;;      esac      case $ac_cv_path_shell in      no)	# Prefer shells that are more likely to be installed in the	# same place on all hosts of this platform.  Therefore, prefer	# shells in /bin and /usr/bin to shells in the installer's	# PATH.  Also, loop through PATH first and then through	# shells, since less-"nice" shells in /bin and /usr/bin are	# more likely to be installed than "nicer" shells elsewhere.	as_save_IFS=$IFS; IFS=:	for as_dir in /bin /usr/bin $PATH	do	  IFS=$as_save_IFS	  case $as_dir in	  /*)	    for ac_base in sh bash ksh sh5; do	      rm -f conftest.c	      if ("$as_dir/$ac_base" -c "$ac_command") 2>/dev/null; then		ac_cv_path_shell=$as_dir/$ac_base		break	      fi	    done	    case $ac_cv_path_shell in	    /*) break;;	    esac;;	  esac	done	rm -f conftest.c;;      esac])   AC_MSG_RESULT($ac_cv_path_shell)   SHELL=$ac_cv_path_shell   if test "$SHELL" = no; then     SHELL=/bin/sh     AC_MSG_WARN([using $SHELL, even though it does not conform to POSIX])   fi   AC_SUBST(SHELL)])