使用chmod可以使用+,-或者=符号给u,g和o三组赋予权限。虽然字面上非常好理解，但是我还是最喜欢直接用八进制组一次性赋值。分享2个自己写的脚本，用来解析权限在字面和八进制之间的快速换算。
字面到八进制组的转换
命令方式为：
p2o.sh permission_text
比如：p2o.sh rwxr-xr–
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# p2o.sh
# permission to octal
# usage: p2o.sh rwxr-xr--
# author: jiechencn@qq.com
permission=$1
for (( i=0; i<${#permission}; i++ )) do
p="${permission:$i:1}"
case "$p" in
r | w | x)
pv="1"
;;
- )
pv="0"
;;
esac
pvs=$pvs$pv
done
p1=`echo $pvs | cut -c 1-3`
p2=`echo $pvs | cut -c 4-6`
p3=`echo $pvs | cut -c 7-9`
echo "permission = "$permission
echo "binary group = "$pvs
echo "octal group = "$((2#$p1))$((2#$p2))$((2#$p3))
八进制组到字面的转换
用法：
o2p.sh octal_group
比如：
o2p.sh 754
这段脚本有个注意的地方，就是每一个八进制数字转换成三位二进制的时候，必须左边补齐0。
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# o2p.sh
# octal to permission
# usage: d2p.sh 731
# author: jiechencn@qq.com
octals=$1
for (( i=0; i<${#octals}; i++ ))
do
d=${octals:$i:1}
b=`echo "obase=2;$d"|bc`
b=`printf "%03d" $b` # 左侧自动补齐0
bs=$bs$b
b1=`echo $b | cut -c 1`
b2=`echo $b | cut -c 2`
b3=`echo $b | cut -c 3`
if [ $b1 == '1' ]
then
ps=$ps"r"
else
ps=$ps"-"
fi
if [ $b2 == '1' ]
then
ps=$ps"w"
else
ps=$ps"-"
fi
if [ $b3 == '1' ]
then
ps=$ps"x"
else
ps=$ps"-"
fi
done
echo "octal group = "$octals
echo "binary group = "$bs
echo "permission = "$ps
最后看一下实际运行
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[oracle@localhost shell]$ p2o.sh rwxr-xr--
permission = rwxr-xr--
binary group = 111101100
octal group = 754
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[oracle@localhost shell]$ o2p.sh 754
octal group = 754
binary group = 111101100
permission = rwxr-xr--