什么时候在Shell脚本中使用＃！/ bin / bash代替＃！/ bin / sh更好？
When you are creating a new shell script, you want to make sure it is as problem free as possible, but sometimes it can be a bit confusing to know which shebang is the best one for you to use. On that note, today’s SuperUser Q&A post has the answer to a confused reader’s question.
在创建新的shell脚本时，您要确保它尽可能没有问题，但是有时知道哪个shebang是最适合您使用的脚本可能会有些混乱。 关于这一点，今天的“超级用户问答”帖子解答了一个困惑的读者的问题。
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.
今天的“问答”环节由SuperUser提供，它是Stack Exchange的一个分支，该社区是由社区驱动的Q＆A网站分组。
问题 (The Question)
SuperUser reader Hendre wants to know when it is better to use #!/bin/bash instead of #!/bin/sh in shell scripts:
超级用户阅读器Hendre想知道何时在shell脚本中使用＃！/ bin / bash而不是＃！/ bin / sh更好：
When is it more appropriate to use #!/bin/bash rather than #!/bin/sh in a shell script?
什么时候在shell脚本中使用＃！/ bin / bash而不是＃！/ bin / sh更合适？
When is it better to use #!/bin/bash instead of #!/bin/sh in a shell script?
什么时候在Shell脚本中使用＃！/ bin / bash代替＃！/ bin / sh更好？
答案 (The Answer)
SuperUser contributor grawity has the answer for us:
超级用户贡献者的感谢为我们提供了答案：
In short:
简而言之：
There are several shells which implement a superset of the POSIX sh specification. On different systems, /bin/sh might be a link to ash, bash, dash, ksh, zsh, etc. It will always be sh-compatible though, never csh or fish.
有几个Shell实现POSIX sh规范的超集。 在不同的系统上， / bin / sh可能是ash，bash，dash，dash，ksh，zsh等的链接。尽管如此，它将始终与sh兼容，而不是csh或fish。
As long as you stick to sh features only, you can (and probably even should) use #!/bin/sh and the script should work fine, no matter which shell it is.
只要仅坚持使用sh功能，就可以(甚至可能应该)使用＃！/ bin / sh ，无论脚本位于哪个shell中，脚本都可以正常工作。
If you start using bash-specific features (i.e. arrays), you should specifically request bash because, even if /bin/sh already invokes bash on your system, it might not on everyone else’s system, and your script will not run there. The same applies to zsh and ksh, of course.
如果您开始使用bash特有的功能(即数组)，则应该特别请求bash，因为即使/ bin / sh已经在系统上调用bash，它也可能不在其他人的系统上运行，并且您的脚本将无法在其中运行。 当然，zsh和ksh也是如此。
Even if the script is for personal use only, you might notice that some operating systems change /bin/sh during upgrades. For example, on Debian it used to be bash, but was later replaced with the very minimal dash. Scripts which used bashisms but had #!/bin/sh suddenly broke.
即使该脚本仅供个人使用，您也可能会注意到某些操作系统在升级过程中会更改/ bin / sh 。 例如，在Debian上它曾经是bash，但后来被极小的破折号所取代。 使用bashisms但具有＃！/ bin / sh的脚本突然中断。
However:
然而：
Even #!/bin/bash is not that correct. On different systems, bash might live in /usr/bin, /usr/pkg/bin, or /usr/local/bin.
甚至＃！/ bin / bash也不是正确的。 在不同的系统上，bash可能位于/ usr / bin ， / usr / pkg / bin或/ usr / local / bin中。
A more reliable option is #!/usr/bin/env bash, which uses $PATH. Although the env tool itself is not strictly guaranteed either, /usr/bin/env still works on more systems than /bin/bash does.
一个更可靠的选项是＃！/ usr / bin / env bash ，它使用$ PATH 。 尽管也没有严格保证env工具本身，但是/ usr / bin / env仍比/ bin / bash在更多的系统上工作。
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