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diff --git a/shelldiag.sh/description b/shelldiag.sh/description
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+Demonstrate some OS and shell detection operations
diff --git a/shelldiag.sh/shelldiag.sh b/shelldiag.sh/shelldiag.sh
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+# Filename: shelldiag.sh
+# License: CC-BY-SA 4.0
+# Author: bgstack15
+# Startdate: 2018-08-14
+# Title: Script That Demonstrates Shell Diagnostics
+# Purpose: To show how to use shell built-ins and shell-independent operations to provide value in other scripts
+# History:
+# Usage:
+# Reference:
+#    man bash ksh
+#    framework.sh 2017-11-11a
+#    zsh filename https://stackoverflow.com/questions/9901210/bash-source0-equivalent-in-zsh/23259585#23259585
+# Improve:
+# Documentation:
+# tested on ksh93 and bash4
+
+detect_os() {
+   # call: detect_os MYOS MYFLAVOR MYFLAVORVERSION
+   __myos="${1:-MYOS}"
+   __myflavor="${2:-MYFLAVOR}"
+   __myflavorversion="${3:-MYFLAVORVERSION}"
+   __thisflavor=""
+   __thisflavorversion=""
+   eval export ${__myos}=\"$( uname -s )\"
+
+   # get __thisflavor and __thisflavorversion. Examples: centos, ubuntu, redhat
+   if test -f /etc/os-release;
+   then
+      eval __thisflavor=$( grep -iE "^\s*ID=" /etc/os-release 2>/dev/null | sed 's/^.*=//;' | tr 'A-Z' 'a-z' )
+      eval __thisflavorversion=$( grep -iE "^\s*PRETTY_NAME=" /etc/os-release 2>/dev/null | sed -e 's/^.*=//;' | tr -dc '0-9.' )
+   elif test -f /etc/system-release && test $( wc -l < /etc/system-release 2>/dev/null ) -eq 1;
+   then
+      eval __thisflavor=$( awk '{print $1}' < /etc/system-release 2>/dev/null | tr 'A-Z' 'a-z' )
+      eval __thisflavorversion=$( </etc/system-release sed -e 's/^.*=//;' 2>/dev/null | tr -dc '0-9.' )
+   else
+      if test "${__myos}" = "FreeBSD"; then
+         __thisflavor="$( uname -i )"; __thisflavorversion="$( uname -r )";
+      else
+         __thisflavor="other"
+         __thisflavorversion="unknown"
+      fi
+   fi
+
+   eval export ${__myflavor}=\"${__thisflavor}\"
+   eval export ${__myflavorversion}=\"${__thisflavorversion}\"
+
+}
+
+detect_shell() {
+   # call: detect_shell MYSHELL MYSOURCED MYSCRIPT MYFUNCTION
+   __myshell="${1:-MYSHELL}"
+   __mysourced="${2:-MYSOURCED}"
+   __myscript="${3:-MYSCRIPT}"
+   __myfunction="${4:-MYFUNCTION}"
+
+   case "$( eval echo \"\$${__myos}\" )" in
+      Linux)
+         eval export ${__myshell}=\"$( readlink -f /proc/$$/exe )\"
+         ;;
+      *)
+         # this works on linux, but Linux has the /proc filesystem
+         eval export ${__myshell}=\"$( ps -p $$ -oargs= | awk '{print $1}' | xargs which | xargs readlink -f )\"
+         ;;
+   esac
+
+   # detect if dot-sourced
+   eval export ${__mysourced}="NOPE"
+   case "${0}" in
+      "-bash"|"ksh")
+         eval export ${__mysourced}="yes"
+         ;;
+      *)
+         # cannot yet determine zsh dot-sourced script
+         eval export ${__mysourced}="no"
+         ;;
+   esac
+
+   # detect which file this is, exactly
+   case "$( eval echo \"\$${__myshell}\" )" in
+      *bash)
+         eval export ${__myscript}=\"$( readlink -f "${BASH_SOURCE}" )\"
+         ;;
+      *ksh*)
+         eval export ${__myscript}=\"$( readlink -f "${.sh.file}" )\"
+         ;;
+      *zsh)
+         eval export ${__myscript}=\"$( readlink -f "${(%):-%x}" )\"
+         ;;
+      *)
+         eval echo "cannot determine myshell \$${__myshell}"
+         ;;
+   esac
+
+   # learn the function name
+   case "$( eval echo \"\$${__myshell}\" )" in
+      *bash)
+         eval export ${__myfunction}=\"${FUNCNAME}\"
+         ;;
+      *ksh*)
+         eval export ${__myfunction}=\"${.sh.fun}\"
+         ;;
+      *zsh)
+         eval export ${__myfunction}=\"$( readlink -f "${(%):-%N}" )\"
+         ;;
+      *)
+         eval echo "cannot determine function for shell \$${__myshell}"
+         ;;
+   esac
+
+}
+
+detect_os MYOS MYFLAVOR MYFLAVORVERSION
+echo "MYOS=${MYOS}"
+echo "MYFLAVOR=${MYFLAVOR}"
+echo "MYFLAVORVERSION=${MYFLAVORVERSION}"
+
+detect_shell MYSHELL MYSOURCED MYSCRIPT MYFUNCTION # assign variable MYHELL with the executable that is running this script
+echo "MYSHELL=${MYSHELL}"
+echo "MYSOURCED=${MYSOURCED}"
+echo "MYSCRIPT=${MYSCRIPT}"
+echo "MYFUNCTION=${MYFUNCTION}"