allenle@backupabc:~$ cat  retrictedshell.sh
 #!/bin/bash 
  echo
  echo "I am in `pwd`" 
  echo "Changing directory." 
  cd /usr 
  echo "New dirctory in `pwd`" 
  echo "Coming back home." 
  cd -
  echo "I am again in `pwd`" 
  echo "--------------------restricted shells------------------------------"
  set -r 
     #or  set --restricted 
  echo "==> Now in restricted mode. <==" 
  echo 
  echo 
  echo "Tring directory change in restricted mode." 
  cd .. 
  echo "I am in `pwd`" 
  echo 
  echo 
         
  echo "\$SHELL = $SHELL" 
  echo "Attempting to change shell in restricted mode." 
  SHELL="/bin/ash" 
  echo 
  echo "\$SHELL= $SHELL" 

  echo 
  echo 

  echo "Attempting to redirect output in restricted mode." 
  ls -l /usr/bin > bin.files 
  ls -l bin.files # Try to list attempted file creation effort. 
  echo 
  exit 0

从结果图看，在非受限模式下，变更目录的操作成功了。

当改变了shell模式为受限模式（set -r），cd命令变更目录的操作就不成功了。

不仅如此，当试图修改$shell变量时，也是失败的。

 注：脚本开头以"#!/bin/bash -r"来调用，则以受限模式运行脚本。