今天木有冷笑话，只有一个噩耗。波浪号展开的目的，是要将用户根目录的符号型表示方式，改为实际的目录路径。shell程序碰到一句命令，都会执行上边的一次流程。eval语句是再告知shell取出eval的参数，并再执行它们一次，是他们经过整个命令行的处理步骤。在步骤1发现|后，将该行分割为两个命令：ls 和more。一般花括号被视为关键字，即它们只有出现在命令的第一个符号时被识别。实际上，这表示你必须将结束花括号放置在换行符或分号之后。这种查找顺序让定义shell函数以扩展或覆盖一般shell内建命令成为可能。举例说你希望shell的提示号能包含当前目录路径的最后一个组成部分。这时候我们需要转义策略，使用内建命令command来告诉shell要避开函数的查找直接访问真正的命令。
](https://downs1.kaledl.com/uploads/images/2021728/255d8a8200074fdb272008b560eb8a0b.png)
](https://downs1.kaledl.com/uploads/images/2021728/08b8d05943c25382d9e510c1f8e4b553.png)
](https://downs1.kaledl.com/uploads/images/2021728/d900903c89d96f2951b71e1f64d2cc0b.png)
](https://downs1.kaledl.com/uploads/images/2021728/21f2ba4c15b3c8b996f9825c9ca7bbb5.png)
](https://downs1.kaledl.com/uploads/images/2021728/e4719f5e2e62458d06b3bf71c8a29f43.png)
](https://downs1.kaledl.com/uploads/images/2021728/a8990a07b9729d1935b3782736a09abe.png)
](https://downs1.kaledl.com/uploads/images/2021728/327c45cd32b893b9bfe9ac3a94107fd7.png)
](https://downs1.kaledl.com/uploads/images/2021728/f7cb78109c4b45aa9d222fbcb568757c.png)
](https://downs1.kaledl.com/uploads/images/2021728/e8a1a983d0d61da77bb2a4b93724327d.png)
](https://downs1.kaledl.com/uploads/images/2021728/3d14f151ef6daf3af6a69b9c99b57c09.png)
](https://downs1.kaledl.com/uploads/images/2021728/16c0dca6b58c9f508f684da857b10de6.png)
](https://downs1.kaledl.com/uploads/images/2021728/e5bbf8a42be6c218c0e730b35ed6a4be.png)
](https://downs1.kaledl.com/uploads/images/2021728/540ea64e9bb0a7242609c3e336b4ca9f.png)
](https://downs1.kaledl.com/uploads/images/2021728/3e2ed244e056ff7a31b53cdcf281bd22.png)
](https://downs1.kaledl.com/uploads/images/2021728/4facc2eee57bb99c714b5be8a7f286ec.png)
](https://downs1.kaledl.com/uploads/images/2021728/8228a2f70f734e71d02f6b252bbf9a43.png)
暂无评论