如何在 Bash 中更改命令行参数？
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How to change a command line argument in Bash?
提问by Sriram
Is there a way to change the command line arguments in a Bash script. Say for example, a Bash script is invoked the following way:
有没有办法在 Bash 脚本中更改命令行参数。例如，Bash 脚本的调用方式如下：
./foo arg1 arg2
Is there a way to change the value of arg1 within the script? Say, something like
有没有办法在脚本中更改 arg1 的值？说，像
="chintz"
回答by thkala
You have to reset all arguments. To change e.g. $3:
您必须重置所有参数。改变例如$3：
$ set -- "${@:1:2}" "new" "${@:4}"
Basically you setallarguments to their current values, except for the one(s) that you want to change. set --is also specified by POSIX 7.
基本上，您将所有参数设置为其当前值，但要更改的参数除外。set --也由 POSIX 7指定。
The "${@:1:2}"notationis expanded to the two (hence the 2in the notation) positional arguments starting from offset 1(i.e. $1). It is a shorthand for "$1" "$2"in this case, but it is much more useful when you want to replace e.g. "${17}".
该"${@:1:2}"表示法扩展为2从偏移量1（即$1）开始的两个（因此在表示法中）位置参数。"$1" "$2"在这种情况下，它是一种简写，但是当您想要替换 eg 时它更有用"${17}"。
回答by Johnsyweb
Optimising for legibility and maintainability, you may be better off assigning $1and $2to more meaningful variables (I don't know, input_filename = $1and output_filename = $2or something) and then overwriting one of those variables (input_filename = 'chintz'), leaving the input to the script unchanged, in case it is needed elsewhere.
优化可读性和可维护性，你可能会更好分配$1和$2更有意义的变量（我不知道，input_filename = $1和output_filename = $2什么的），然后重写这些变量（input_filename = 'chintz'），使输入到脚本不变的情况下，它是其他地方需要。
