shell条件判断 条件为何值时判断语句为真

#!/bin/bash

if [ 0 ]

then

echo "0 is true"

else

echo "0 is flase"

fi

if [ 1 ]

then

echo "1 is true"

else

echo "1 is flase"

fi

if [ -1 ]

then

echo "-1 is true"

else

echo "-1 is flase"

fi

if [ 10 ]

then

echo "10 is true"

else

echo "10 is flase"

fi

if [ ]

then

echo "NULL is true"

else

echo "NULL is flase"

fi

if [ xyz ]

then

echo "xyz is true"

else

echo "xyz is flase"

fi

xyz=

if [ -n "$xyz" ]

then

echo "$xyz is true"

else

echo "\$xyz is flase"

fi

exit 0

# ./test.sh 输出判断

0 is true

1 is true

-1 is true

10 is true

NULL is flase

xyz is true

$xyz is flase