如何编写一个带或不带参数的脚本？

Question

我有一个 bash 脚本，它是这样的：

#!/bin/bash

if [ $1 = "--test" ] || [ $1 = "-t" ]; then
    echo "Testing..."
    testing="y"

else
    testing="n"
    echo "Not testing."

fi

所以我想要做的不仅是用./script --testor运行它./script -t，而且不带参数（只是./script），但似乎如果我用当前代码这样做，输出只是：

./script: line 3: [: =: unary operator expected
./script: line 3: [: =: unary operator expected
Not testing.

那么我如何对其进行编程，以便在没有任何参数的else情况下运行它只会在不抛出错误的情况下执行该操作？我究竟做错了什么？

Answer 1

几种方式；最明显的两个是：

• 放入$1双引号：if [ "$1" = "--test" ]
• 使用 $# 检查参数的数量

更好的是，使用 getopts。

Answer 2

您需要在 if 条件中引用您的变量。代替：

if [ $1 = "--test" ] || [ $1 = "-t" ]; then

和：

if [ "$1" = '--test' ] || [ "$1" = '-t' ]; then  

然后它将起作用：

? ~ ./test.sh
不测试。

始终双引号您的变量！

Answer 3

在 shell 脚本中使用长选项的“正确方法”是通过getopt GNU 实用程序。还有bash 内置的 getopts，但它只允许诸如-t. 可以在此处getopt找到一些用法示例。

这是一个演示我如何处理你的问题的脚本。大多数步骤的说明都作为注释添加到脚本本身中。

#!/bin/bash

# GNU getopt allows long options. Letters in -o correspond to
# comma-separated list given in --long.

opts=$(getopt -o t --long test -- "$*")
test $? -ne 0 && exit 2 # error happened

set -- $opts # some would prefer using eval set -- "$opts"
# if theres -- as first argument, the script is called without
# option flags
if [ "$1" = "--"  ]; then
    echo "Not testing"
    testing="n"
    # Here we exit, and avoid ever getting to argument parsing loop
    # A more practical case would be to call a function here
    # that performs for no options case
    exit 1
fi

# Although this question asks only for one 
# option flag, the proper use of getopt is with while loop
# That's why it's done so - to show proper form.
while true; do
    case "$1" in
        # spaces are important in the case definition
        -t | --test ) testing="y"; echo "Testing" ;;
    esac
    # Loop will terminate if there's no more  
    # positional parameters to shift
    shift  || break
done

echo "Out of loop"

通过一些简化和删除注释，可以将其简化为：

#!/bin/bash
opts=$(getopt -o t --long test -- "$*")
test $? -ne 0 && exit 2 # error happened
set -- $opts    
case "$1" in
    -t | --test ) testing="y"; echo "Testing";;
    --) testing="n"; echo "Not testing";;
esac