#!/bin/sh

# @(#) s3       Demonstrate display of current shell.

## command "ps $$" produces something like:
#  19746 pts/1    S+     0:00 bash
#      1     2     3        4    5

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version =o $(_eat $0 $1) bash3 tcsh ksh zsh dash rc
set -o nounset
echo

echo " Typical results from command ps looks like the first; the"
echo " second may be needed on some systems (e.g. Solaris 10):"

bash <<'EOF'
ps $$

echo
ps | grep $$
EOF

echo
echo " Result of pipeline to isolate the name of the shell:"
bash <<'EOF'
ps $$ |
tail -1 |
sed 's/  */ /g' |
cut -d" " -f5
EOF

echo
echo " Results from various shells (note rc difference)"
echo " using these commands. The variable SHELL is rarely"
echo " updated to reflect the current shell:
 1) ps
 2) cat proc/\$$/cmdline (needs newline)
 3) echo \$SHELL
 4) env | grep -i shell
"
echo

echo " Expecting bash3"
bash3 <<'EOF'
ps $$
cat /proc/$$/cmdline
echo
echo $SHELL
env | grep -i shell
EOF

echo
echo " Expecting tcsh"
tcsh <<'EOF'
ps $$
cat /proc/$$/cmdline
echo
echo $SHELL
env | grep -i shell
EOF

echo
echo " Expecting ksh"
ksh <<'EOF'
ps $$
cat /proc/$$/cmdline
echo
echo $SHELL
env | grep -i shell
EOF

echo
echo " Expecting zsh"
zsh <<'EOF'
ps $$
cat /proc/$$/cmdline
echo
echo $SHELL
env | grep -i shell
EOF

echo
echo " Expecting dash"
dash <<'EOF'
ps $$
cat /proc/$$/cmdline
echo
echo $SHELL
env | grep -i shell
EOF

echo
echo " Expecting rc"
rc <<'EOF'
ps $pid
# cat /proc/$$/cmdline
cat /proc/$pid/cmdline
echo
echo $SHELL
env | grep -i shell
EOF

exit 0

% ./s3

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
Linux 2.6.11-x1
GNU bash, version 2.05b.0(1)-release (i386-pc-linux-gnu)
GNU bash 3.00.16(1)-release
tcsh 6.13.00
pdksh 5.2.14 99/07/13.2
zsh 4.2.4
dash - no version provided for /bin/dash.
rc 1.7.1

 Typical results from command ps looks like the first; the
 second may be needed on some systems (e.g. Solaris 10):
  PID TTY      STAT   TIME COMMAND
 1125 pts/2    S+     0:00 bash

 1125 pts/2    00:00:00 bash

 Result of pipeline to isolate the name of the shell:
0:00

 Results from various shells (note rc difference)
 using these commands. The variable SHELL is rarely
 updated to reflect the current shell:
 1) ps
 2) cat proc/$$/cmdline (needs newline)
 3) echo $SHELL
 4) env | grep -i shell


 Expecting bash3
  PID TTY      STAT   TIME COMMAND
 1134 pts/2    R+     0:00 bash3
bash3
/bin/tcsh
SHELL=/bin/tcsh

 Expecting tcsh
  PID TTY      STAT   TIME COMMAND
 1139 pts/2    S+     0:00 tcsh
tcsh
/bin/tcsh
SHELL=/bin/tcsh

 Expecting ksh
  PID TTY      STAT   TIME COMMAND
 1178 pts/2    S+     0:00 ksh
ksh
/bin/tcsh
SHELL=/bin/tcsh

 Expecting zsh
  PID TTY      STAT   TIME COMMAND
 1183 pts/2    S+     0:00 zsh
zsh
/bin/tcsh
SHELL=/bin/tcsh

 Expecting dash
  PID TTY      STAT   TIME COMMAND
 1188 pts/2    S+     0:00 dash
dash
/bin/tcsh
SHELL=/bin/tcsh

 Expecting rc
  PID TTY      STAT   TIME COMMAND
 1193 pts/2    S+     0:00 rc
rc
/bin/tcsh
SHELL=/bin/tcsh

echo #SHELL

help

echo #SHELL