SHELL逻辑操作符

1.逻辑与

if [ cond1 -a cond2 ];

then

    do something;

elif [ cond1 ] && [ cond2 ]

then

    do something;

else

    do something;

fi;

2.逻辑或

if [ cond1 -o cond2 ];

then

    do something;

elif [ cond1 ] || [ cond2 ]

then

    do something;

else

    do something;

fi;

3.逻辑非

if [ ！ cond1 ];

then

    do something;

else

    do something;

fi;