bash的不同条件测试方法

#!/bin/bash
# Using the old style test command
# filename: perm_check
file=./testing
if [ -d $file ]
then
 echo "$file is a directory"
elif [ -f $file ]
then
 if [ -r $file -a -w $file -a -x $file ]
 then                # nested if command
   echo "You have read,write,and execute \
   permission on $file."
 fi
else
 echo "$file is neither a file nor a directory. "
fi

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#!/bin/bash   
# Using the new compound operator for test (( ))
# filename: perm_check2

file=./testing

if [[ -d $file ]]  
then
 echo "$file is a directory"
elif [[ -f $file ]]
then
 if [[ -r $file && -w $file && -x $file ]]
 then     # nested if command
   echo "You have read,write,and execute \
   permission on $file."
 fi
else
 echo "$file is neither a file nor a directory. "
fi