check shell correctly

which.spec

@@ -1,7 +1,7 @@
 Summary: Displays where a particular program in your path is located
 Name: which
 Version: 2.21
-Release: 30%{?dist}
+Release: 31%{?dist}
 License: GPLv3
 Source0: http://ftp.gnu.org/gnu/which/%{name}-%{version}.tar.gz
 Source1: which2.sh
@@ -41,6 +41,9 @@ rm -f $RPM_BUILD_ROOT%{_infodir}/dir
 %{_mandir}/man1/which.1*
 
 %changelog
+* Thu Dec 02 2021 Than Ngo <than@redhat.com> - 2.21-31
+- check shell correctly
+
 * Tue Oct 26 2021 Than Ngo <than@redhat.com> - 2.21-30
 - disable the --read-functions option in korn shells
 

which2.sh

@@ -1,8 +1,8 @@
 # shellcheck shell=sh
 # Initialization script for bash, sh, mksh and ksh
 
-case "$(cat /proc/$$/comm)" in
-ksh|mksh)
+case "$(basename $(readlink /proc/$$/exe))" in
+*ksh*)
     which_declare=""
     which_opt=""
     ;;
@@ -10,10 +10,14 @@ zsh)
     which_declare="typeset -f"
     which_opt=""
     ;;
-*)
+bash|sh)
     which_declare="declare -f"
     which_opt="-f"
     ;;
+*)
+    which_declare=""
+    which_opt=""
+    ;;
 esac
 
 which () {