Shell语言高级用法探索

# 定义数组
my_array=(one two three four five)

# 访问数组元素
echo ${my_array[0]}  # 输出: one
echo ${my_array[3]}  # 输出: four

# 遍历数组
for element in "${my_array[@]}"; do
    echo $element
done

# 声明关联数组
declare -A my_assoc_array

# 赋值
my_assoc_array[key1]="value1"
my_assoc_array[key2]="value2"

# 访问元素
echo ${my_assoc_array[key1]}  # 输出: value1

# 遍历关联数组
for key in "${!my_assoc_array[@]}"; do
    echo "$key: ${my_assoc_array[$key]}"
done

# 定义函数
my_function() {
    echo "Hello, this is a function!"
}

# 调用函数
my_function

# 计算阶乘的递归函数
factorial() {
    if [ $1 -le 1 ]; then
        echo 1
    else
        local temp=$(( $1 - 1 ))
        local prev=$(factorial $temp)
        echo $(( $1 * $prev ))
    fi
}

# 调用递归函数
result=$(factorial 5)
echo "Factorial of 5 is: $result"  # 输出: 120

# 使用反引号
current_date=`date`
echo "Current date and time: $current_date"

# 使用$()语法（推荐）
current_date=$(date)
echo "Current date and time: $current_date"

# 在子Shell中执行命令
(
    cd /some/directory
    echo "Current directory in subshell: $(pwd)"
)

# 注意：子Shell中的变量不会影响到父Shell

# 使用if语句
if [ $a -gt $b ]; then
    echo "$a is greater than $b"
elif [ $a -eq $b ]; then
    echo "$a is equal to $b"
else
    echo "$a is less than $b"
fi

# 使用case语句
case $variable in
    pattern1)
        echo "Pattern 1 matched"
        ;;
    pattern2)
        echo "Pattern 2 matched"
        ;;
    *)
        echo "No pattern matched"
        ;;
esac

# for循环
for i in {1..5}; do
    echo "Number: $i"
done

# while循环
counter=1
while [ $counter -le 5 ]; do
    echo "Counter: $counter"
    ((counter++))
done

# until循环
counter=1
until [ $counter -gt 5 ]; do
    echo "Counter: $counter"
    ((counter++))
done

# 使用-x选项进行调试
bash -x script.sh

# 在脚本中设置调试选项
set -x  # 开启调试
# ... 脚本代码 ...
set +x  # 关闭调试

# 使用if语句检查命令是否成功
command_that_might_fail
if [ $? -ne 0 ]; then
    echo "Command failed"
    exit 1
fi

# 使用trap捕获错误
trap 'echo "An error occurred. Exiting..."; exit 1' ERR

# 使用set -e自动退出脚本
set -e
# ... 脚本代码 ...
# 任何命令失败都会立即退出脚本