shell 报错：unary operator expected"
2014-08-29 11:47
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一直学习perl，shell都忘得差不多了，今天写了个小脚本，判断脚本第二个变量不等于某字符串时的操作。
if [ $? -eq 0 ] && [ $2 != "wp" ]
then
: #略
fi
如果不加第二个变量，运行时会出现[: !=: unary operator expected"的报错，最后调试时发现
[ != "wp"]
原来shell的变量不定义时会出现这种情况，那就直接双括号吧。
[[ != "wp"]]
if [ $? -eq 0 ] && [ $2 != "wp" ]
then
: #略
fi
如果不加第二个变量，运行时会出现[: !=: unary operator expected"的报错，最后调试时发现
[ != "wp"]
原来shell的变量不定义时会出现这种情况，那就直接双括号吧。
[[ != "wp"]]
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