[:shell编程中的意外操作符

Question

我的代码:

    #!/bin/sh
    #filename:choose.sh
    read choose
    [ "$choose" == "y" -o "$choose" == "Y" ] && echo "Yes" && exit 0
    [ "$choose" == "n" -o "$choose" == "N" ] && echo "No"  && exit 0
    echo "Wrong Input" && exit 0

但是当我执行时

    sh ./choose.sh

终端提示我

   [: 4: n: :Unexpected operator
   [: 5: n: :Unexpected operator

我的bash脚本有什么错误吗？谢谢!

Answer 1

你的bash脚本没有错误.但是你用sh执行它,它的语法不太广泛;)

所以,bash ./choose.sh改为运行:)

Answer 2

POSIX sh不了解==字符串相等性,因为这是一种bash -ism.请=改用.

其他人说sh不支持括号是错误的,顺便说一句.

Answer 3

To execute it with Bash, use #!/bin/bash and chmod it to be executable, then use

./choose.sh

Answer 4

你必须使用bash代替或使用标准sh重写你的脚本

sh -c 'test "$choose" = "y" -o "$choose" = "Y"'

Answer 5

In fact the "[" square opening bracket is just an internal shell alias for the test command.

So you can say:

test -f "/bin/bash" && echo "This system has a bash shell"

or

[ -f "/bin/bash" ] && echo "This system has a bash shell"

... they are equivalent in either sh or bash. Note the requirement to have a closing "]" bracket on the "[" command but other than that "[" is the same as "test". "man test" is a good thing to read.

Answer 6

你可以使用case/esac而不是if/else

case "$choose" in
  [yY]) echo "Yes" && exit;;
  [nN]) echo "No" && exit;;
  * ) echo "wrong input" && exit;;
esac