asterisk/autoconf/ast_prog_sed.m4

# AST_PROG_SED
# -----------
# Check for a fully functional sed program that truncates
# as few characters as possible.  Prefer GNU sed if found.
AC_DEFUN([AST_PROG_SED],
[AC_CACHE_CHECK([for a sed that does not truncate output], ac_cv_path_SED,
    [dnl ac_script should not contain more than 99 commands (for HP-UX sed),
     dnl but more than about 7000 bytes, to catch a limit in Solaris 8 /usr/ucb/sed.
     ac_script=s/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/
     for ac_i in 1 2 3 4 5 6 7; do
       ac_script="$ac_script$as_nl$ac_script"
     done
     echo "$ac_script" | sed 99q >conftest.sed
     $as_unset ac_script || ac_script=
     ifdef([_AC_PATH_PROGS_FEATURE_CHECK], [_AC_PATH_PROGS_FEATURE_CHECK], [_AC_PATH_PROG_FEATURE_CHECK])(SED, [sed gsed],
	[_AC_FEATURE_CHECK_LENGTH([ac_path_SED], [ac_cv_path_SED],
		["$ac_path_SED" -f conftest.sed])])])
 SED="$ac_cv_path_SED"
 AC_SUBST([SED])dnl
 rm -f conftest.sed
])# AST_PROG_SED