linux 判断指定用户对指定目录具有的权限

#!/bin/sh  
username3=$1  
dir_name2=$2  
  
# get existing directory  
file_path=$dir_name2  
while true  
do  
        if [ -d $file_path ];then  
                break;  
        fi  
        file_path=${file_path%/*}  
done  
dir_name2=$file_path  
  
# Judge whether the user exists  
grep "^$username3:" /etc/passwd >/dev/null  
if [ $? -ne 0 ];then  
    echo "This user \"$username3\" does not exist."  
    exit 4  
fi  
#echo "username : $username3"  
group4=` grep "^$username3:"  /etc/passwd |awk -F : {‘print $4‘}|xargs  -i  grep {}  /etc/group|cut -d":" -f1`  
#echo "group : $group4"  
su -l $username3 -c "test -r $dir_name2"  
is_read=$?  
su -l $username3 -c "test -x $dir_name2"  
is_exe=$?  
su -l $username3 -c "test -w $dir_name2"  
is_write=$?  
$is_read_str  
$is_exe_str  
$is_write_str  
if [ $is_read -eq 0 ];then  
    is_read_str="r"  
else  
    is_read_str="-"  
fi  
  
if [ $is_exe -eq 0 ];then  
        is_exe_str="x"  
else  
        is_exe_str="-"  
fi  
  
if [ $is_write -eq 0 ];then  
        is_write_str="w"  
else  
        is_write_str="-"  
fi  
  
  
echo "${is_read_str}${is_write_str}${is_exe_str}"