[root@dev ~]# env
HOSTNAME=localhost
TERM=linux
SHELL=/bin/bash
HISTSIZE=1000
SSH_CLIENT=10.0.100.17 56344 22
SSH_TTY=/dev/pts/0
USER=root


[root@dev ~]# 
[root@dev ~]# printenv
HOSTNAME=localhost
TERM=linux
SHELL=/bin/bash
HISTSIZE=1000
SSH_CLIENT=10.0.100.17 56344 22
SSH_TTY=/dev/pts/0
USER=root


[root@dev ~]# printenv TERM
linux

[root@dev ~]# echo $HOME
/root

[root@dev ~]# set
BASH=/bin/bash
BASHOPTS=checkwinsize:cmdhist:expand_aliases:extquote:force_fignore:hostcomplete:interactive_comments:login_shell:progcomp:promptvars:sourcepath
BASH_ALIASES=()
BASH_ARGC=()
BASH_ARGV=()
BASH_CMDS=()
BASH_LINENO=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="4" [1]="1" [2]="2" [3]="1" [4]="release" [5]="x86_64-redhat-linux-gnu")
BASH_VERSION='4.1.2(1)-release'
COLORS=/etc/DIR_COLORS
COLUMNS=165

[root@dev shell]# sh a.sh

2
22
2
[root@dev shell]# cat a.sh
#!/bin/bash

a=1;
export b=2;

sh b.sh

echo $b;


[root@dev shell]# cat b.sh
#!/bin/bash

echo $a;
echo $b;
b=22;
echo $b;
[root@dev shell]# sh a.sh 

2
22
2

[root@dev shell]# cat c.sh
. ./env.sh
source ./profile.sh

echo $env;
echo $profile;
[root@dev shell]# cat env.sh
env='test';
[root@dev shell]# cat profile.sh 
profile="dev";
[root@dev shell]# sh c.sh 
test
dev

unset var_name

[root@dev shell]# cat /etc/profile
# /etc/profile

# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc

# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.

pathmunge () {
 case ":${PATH}:" in
  *:"$1":*)
   ;;
  *)
   if [ "$2" = "after" ] ; then
    PATH=$PATH:$1
   else
    PATH=$1:$PATH
   fi
 esac
}


if [ -x /usr/bin/id ]; then
 if [ -z "$EUID" ]; then
  # ksh workaround
  EUID=`id -u`
  UID=`id -ru`
 fi
 USER="`id -un`"
 LOGNAME=$USER
 MAIL="/var/spool/mail/$USER"
fi

# Path manipulation
if [ "$EUID" = "0" ]; then
 pathmunge /sbin
 pathmunge /usr/sbin
 pathmunge /usr/local/sbin
else
 pathmunge /usr/local/sbin after
 pathmunge /usr/sbin after
 pathmunge /sbin after
fi

HOSTNAME=`/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
 export HISTCONTROL=ignoreboth
else
 export HISTCONTROL=ignoredups
fi

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL

# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
 umask 002
else
 umask 022
fi

for i in /etc/profile.d/*.sh ; do
 if [ -r "$i" ]; then
  if [ "${-#*i}" != "$-" ]; then
   . "$i"
  else
   . "$i" >/dev/null 2>&1
  fi
 fi
done

unset i
unset -f pathmunge

[root@dev shell]# cat ~/.bash_profile 
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
  . ~/.bashrc
fi

# User specific environment and startup programs

PATH=$PATH:$HOME/bin

export PATH