在没有商店时设置expand_alias? [英] Set expand_alias when shopt not available?

问题描述

我正在尝试在正在编写的Shell脚本中使用别名，但无法正常工作.

I'm trying to use an alias in a shell script I'm writing, but it is not working.

别名:

alias ts="awk '{ print strftime(\"[%Y-%m-%d %H:%M:%S]\"), \$0 }'"

运行脚本时，出现以下错误:

When I run the script, I get the following error:

./copyTask.sh: ts: not found

在互联网上闲逛，似乎我需要启用 expand_aliases shell选项，但是我没有安装 shopt ...有什么办法吗?我可以启用别名扩展，而无需使用 shopt 或创建另一个rootfs映像?

Sooping around on the internet, it seems that I need to enable the expand_aliases shell option, but I don't have shopt installed... Is there any way I can enable alias expansion without using shopt or creating another rootfs image?

我正在使用 ash 外壳.而 awk 是BusyBox v1.25.0 awk .

I'm using the ash shell. And awk is BusyBox v1.25.0 awk.

注意:别名是在时间戳前面加上命令的简单方法:

NOTE: The alias is an easy way to prepend a timestamp to a commmand:

$ echo "foo" | ts
[2005-06-23 11:52:32] foo

由于某些人难以理解我的意思，此答案有一个例子.

as some people are having trouble understanding what I mean, this answer has an example.

推荐答案

不要在脚本中使用别名.函数执行相同的功能更好.

Don't use aliases in scripts. A function does the same job better.

ts() { gawk '{ print strftime("[%Y-%m-%d %H:%M:%S]"), $0 }' "$@"; }

• 这适用于任何POSIX shell，包括根本不支持别名的shell.
• 这适用于非交互式外壳，而无需显式启用别名支持.
• 这可以通过别名无法扩展的方式来扩展(可以将条件逻辑放入函数中；可以将参数置于函数中非尾部的位置；等等).
• 在bash中，可以将函数导出到环境中: export -f ts 将使 ts 命令可用于子进程(它们运行的​​shell也是bash)
• This works with any POSIX shell, including ones that don't support aliases at all.
• This works with noninteractive shells without needing to enable alias support explicitly.
• This can be extended in ways that aliases can't (you can put conditional logic inside functions; you can put arguments in non-tail positions in functions; etc).
• In bash, functions can be exported to the environment: export -f ts will make the ts command available to subprocesses (where the shell they run is also bash).

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