linux - 学习 Bash 条件 - 语法错误

Question

好的。我一直在用头撞 Linux 的墙。我在这里做错了什么:

#! /bin/bash
echo
echo "1. Windows (Microsoft)
echo  2. Linux (Red Hat)
echo  3. MacOS (Apple)
echo
echo -n Select your OS choice [1, 2 or 3]: "
READ OS
echo

if [ "$OS" -eq 1 ]; then
echo "You picked Windows (Microsoft)."
fi
if [ "$OS" -eq 2 ]; 
echo "You picked Linux (Red Hat)."
fi
if [ "$OS" -eq 3 ]; then
echo "You picked MacOS (Apple)."
fi
if [ "$OS" > 3 || "$OS" < 1 ]];
echo "Invalid selection!"
fi
exit 1

错误信息:

[ : : integer expression expected

Answer 1

你使用了错误的 if/elif/else 语法:

if [ "$OS" -eq 1 ] 
then
    echo "You picked Windows (Microsoft)."
elif [ "$OS" -eq 2 ] 
then 
     echo "You picked Linux (Red Hat)."
elif [ "$OS" -eq 3 ] 
then
     echo "You picked MacOS (Apple)."
else 
     echo "Invalid selection!"
fi
exit 1

此外，如果您想使用更大或更差，您应该使用 -gt 或 -lt 等。请引用此页面:http://tldp.org/LDP/abs/html/comparison-ops.html

还可以通过以下链接查看 or 和 and 的语法:http://tldp.org/LDP/abs/html/ops.html#ANDOR

此外，我刚刚发现您的左方括号数量应该与右方括号数量相同。

修复脚本中的所有问题后:

#! /bin/bash

echo
echo "1. Windows (Microsoft)"
echo "2. Linux (Red Hat)"
echo "3. MacOS (Apple)"
echo
echo -n "Select your OS choice [1, 2 or 3]: "
read OS
echo

if [ "$OS" -eq 1 ] 
then
    echo "You picked Windows (Microsoft)."
elif [ "$OS" -eq 2 ] 
then 
     echo "You picked Linux (Red Hat)."
elif [ "$OS" -eq 3 ] 
then
     echo "You picked MacOS (Apple)."
else 
     echo "Invalid selection!"
fi
exit 0

在执行时产生以下输出:

arobert@arobert-VirtualBox [11:48:52]
[/home/arobert/test_awk] >
./ostype.sh 

1. Windows (Microsoft)
2. Linux (Red Hat)
3. MacOS (Apple)

Select your OS choice [1, 2 or 3]: 2

You picked Linux (Red Hat).
arobert@arobert-VirtualBox [11:48:56]
[/home/arobert/test_awk] >
./ostype.sh 

1. Windows (Microsoft)
2. Linux (Red Hat)
3. MacOS (Apple)

Select your OS choice [1, 2 or 3]: 1

You picked Windows (Microsoft).
arobert@arobert-VirtualBox [11:49:00]
[/home/arobert/test_awk] >
./ostype.sh 

1. Windows (Microsoft)
2. Linux (Red Hat)
3. MacOS (Apple)

Select your OS choice [1, 2 or 3]: 3 

You picked MacOS (Apple).
arobert@arobert-VirtualBox [11:49:05]
[/home/arobert/test_awk] >
./ostype.sh 

1. Windows (Microsoft)
2. Linux (Red Hat)
3. MacOS (Apple)

Select your OS choice [1, 2 or 3]: 5

Invalid selection!