"$#"代表什么卑鄙的意思? [英] What does "$#" mean in bash?

问题描述

我有一个与此相关的脚本:

I have a script with this:

login {
    # checking parameters -> if not ok print error and exit script
    if [ $# -lt 2 ] || [ $1 == '' ] || [ $2 == '' ]; then
        echo "Please check the needed options (username and password)"
        echo ""
        echo "For further Information see Section 13"
        echo ""
        echo "Press any key to exit"
        read
        exit
    fi

  } # /login

但是我真的不知道$#在第三行的含义.

But I really dont know what the $# means on the third line.

推荐答案

井号很重要.

1. 如果只是$#，则是位置参数的数量，例如$1，$2，$3. (请注意，不算$0.)
2. 如果为${#var}，则为参数扩展中的字符数. (字符串长度)
3. 如果为${#var[@]}，则为数组中元素的数量.由于bash数组稀疏，因此可以与最后一个元素的索引加一个不同.

1. If it's just $#, it's the number of positional parameters, like $1, $2, $3. (Not counting $0, mind you.)
2. If it's ${#var}, it's the number of characters in the expansion of the parameter. (String length)
3. If it's ${#var[@]}, it's the number of elements in the array. Since bash arrays are sparse, this can be different from the index of the last element plus one.

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