tests: avoid grep in init.sh

* tests/init.sh (warn_, gl_shell_test_script_):
Avoid the use of grep, as that introduces an unwanted dependency.
On older systems like Solaris there can be many greps and they
can be buggy, so it’s better to not rely on them in a central
part of the test harness.

ChangeLog

@@ -1,5 +1,12 @@
 2025-09-21  Paul Eggert  <eggert@cs.ucla.edu>
 
+	tests: avoid grep in init.sh
+	* tests/init.sh (warn_, gl_shell_test_script_):
+	Avoid the use of grep, as that introduces an unwanted dependency.
+	On older systems like Solaris there can be many greps and they
+	can be buggy, so it’s better to not rely on them in a central
+	part of the test harness.
+
 	tests: avoid test failure due to rmdir race
 	* tests/init.sh (remove_tmp_): If the rm -rf fails, wait a second
 	and try again.  This works around a problem I observed on Solaris

tests/init.sh

@@ -103,7 +103,11 @@ warn_ ()
   case $IFS in
     ' '*) printf '%s\n' "$*" >&2
           test $stderr_fileno_ = 2 \
-            || { printf '%s\n' "$*" | sed 1q >&$stderr_fileno_ ; } ;;
+            || { local args=$*
+                 local firstline=${args%%"$gl_init_sh_nl_"*}
+                 printf '%s\n' "$firstline" >&$stderr_fileno_
+               }
+          ;;
     *) (IFS=' '; warn_ "$@");;
   esac
 }
@@ -160,12 +164,12 @@ fi
 #  ? - not ok
 gl_shell_test_script_='
 test $(echo y) = y || exit 1
-LC_ALL=en_US.UTF-8 printf "\\351" 2>/dev/null \
-  | LC_ALL=C tr "\\351" x | LC_ALL=C grep "^x$" > /dev/null \
-  || exit 1
-printf "\\351" 2>/dev/null \
-  | LC_ALL=C tr "\\351" x | LC_ALL=C grep "^x$" > /dev/null \
-  || exit 1
+case $({ LC_ALL=en_US.UTF-8 printf "\\351"
+         printf "\\351\\n"
+       } 2>/dev/null | LC_ALL=C tr "\\351" x) in
+  xx) ;;
+  *) exit 1;;
+esac
 f_local_() { local v=1; }; f_local_ || exit 1
 f_dash_local_fail_() { local t=$(printf " 1"); }; f_dash_local_fail_
 score_=10