#!/bin/bash
# shellselector by Marco Mambelli, marco@hep.uchciago.edu
# Expects the parent process to be a shell and provides its name
# Used to select a shell dependent setup from an insependent one:
# source setup.`./shellselector -q`
# Without "-q" it prints informations about the shell detected
#
# Tests show that $SHELL is unreliable
# Current shell is needed, not the login shell
#
if [ "X${1}X" == "X-hX" ]
then
 echo "$0 [-h|-q]"
 echo "         detects a shell and shell family"
 echo " -h      prints this help message"
 echo " -q      quiet, prints only the shell family (sh or csh)"
 exit
fi

MYSHELL="`ps -o ppid= -p $$ | xargs ps -o comm= -p `"
MYSHELL_ORIG=$MYSHELL

# If ps fails, fall back to $SHELL
# There could be euristics (all in the environment of the parent process ps -wwwE -p PPID):
# 1. $version is set on tcsh
# 2. $BASH is set on bash
# 3. $shell (lowercase) is set to actual shell name in csh or tcsh
# 4. $ZSH_NAME is set on zsh
# 5. ksh has $PS3 and $PS4

# It seems for a bug, csh login shell is called "-sh" (at least on OS X)
if [ "X$MYSHELL" == "X-sh" ]; then
 MYSHELL="csh"
fi

if [[ "X$MYSHELL" == "Xlogin" && ! -z $SHELL ]]; then
 MYSHELL="`basename $SHELL`"
fi

# Remove the leading dash for login shells
# and the directory (/bin, /usr/bin or none)
MYSHELL="`basename ${MYSHELL#-}`"

# change the case statement below to have different setup files for ksh or zsh
# Fail-safe to sh when unknown (if -q option)
case "$MYSHELL" in
 bash|sh) SHELLFAM="sh";;
 ksh) SHELLFAM="sh";;
 zsh) SHELLFAM="sh";;
 tcsh|csh) SHELLFAM="csh";;
 *) if [ "X${1}X" == "X-qX" ]
    then SHELLFAM="sh"
    else echo "Unknown shell $MYSHELL"; exit 1
    fi;;
esac
if [ "X${1}X" == "X-qX" ]
then echo "$SHELLFAM"
else echo "Your shell is $MYSHELL ($MYSHELL_ORIG), of type $SHELLFAM"
fi