如何在 Common Lisp 中迭代目录？

发布于 2024-08-04 12:34:05 字数 261 浏览 5 评论 0原文

我在 Darwin 上使用 OpenMCL，我想做一些类似的事情：

(loop for f in (directory "somedir")
  collect (some-per-file-processing f))

但是我无法让 directory 返回除 NIL 以外的任何内容，而且我可以'似乎在网上找不到任何好的解释（除了“每个系统的不同”）。

有什么指点吗？

原文

I'm using OpenMCL on Darwin, and I'd like to do something like:

(loop for f in (directory "somedir")
  collect (some-per-file-processing f))

But I can't get directory to return anything other than NIL, and I can't seem to find any good explanation online (other than "its different for each system").

Any pointers?

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心头的小情儿 2024-08-11 12:34:05

基本上有两种指定路径名的方法：

使用字符串

字符串显然取决于平台：例如 Unix 语法与 Windows 语法。

"/Users/foo/bar.text"  is a valid pathname
"/Users/foo/*/foo.*"   is a valid pathname with two wildcards

您可以从字符串创建路径名对象：

? (pathname "/Users/bar/foo.text")
#P"/Users/bar/foo.text"

上面的 #p 确保在您读回路径名对象（而不是字符串）时创建它。

? #P"/Users/bar/foo.text"
#P"/Users/bar/foo.text"

因此，Common Lisp 在内部使用路径名对象，但它允许您使用普通字符串并根据需要从它们创建路径名对象。

当 Common Lisp 发现路径名未指定所有组件（例如缺少目录）时，它会从路径名对象中填充组件，该对象是变量 *DEFAULT-PATHNAME-DEFAULTS* .

使用 DESCRIBE 函数，您可以查看路径名的组成部分（此处为 Clozure CL）：

? (describe (pathname "/Users/bar/*.text"))
#P"/Users/bar/*.text"
Type: PATHNAME
Class: #<BUILT-IN-CLASS PATHNAME>
TYPE: (PATHNAME . #<CCL::CLASS-WRAPPER PATHNAME #x3000401D03BD>)
%PATHNAME-DIRECTORY: (:ABSOLUTE "Users" "bar")
%PATHNAME-NAME: :WILD
%PATHNAME-TYPE: "text"
%PHYSICAL-PATHNAME-VERSION: :NEWEST
%PHYSICAL-PATHNAME-DEVICE: NIL

使用 Lisp 函数创建路径名对象

MAKE-PATHNAME是函数，它需要一些关键字参数来指定组件。

有时，基于现有路径名创建新路径名也很有用：

(make-pathname :name "foo" :defaults (pathname "/Users/bar/baz.text"))

如果使用函数DIRECTORY，则使用带通配符的路径名会很有用。 DIRECTORY 然后将返回匹配路径名的列表。名称DIRECTORY 有点误导，因为DIRECTORY 不列出目录的内容，而是列出（通常）带有通配符的路径名的匹配路径名。通配符可以匹配 /foo/s*c/list*.l* 等组件中的字符序列。还有通配符 ** ，用于匹配目录层次结构的一部分，例如 /foo/**/test.lisp ，它匹配所有文件 test.lisp 位于目录 foo 及其子目录下。

(directory "/Users/foo/Lisp/**/*.lisp")

上面应该返回 /Users/foo/Lisp/ 及其所有子目录中的所有 lisp 文件的列表。

要返回单个目录中的 .c 文件，请使用：

(directory "/Users/foo/c/src/*.c")

请注意，DIRECTORY 返回 pathname 对象列表（而不是字符串列表）。

? (directory
    (make-pathname
      :name "md5"
      :type :wild
      :directory '(:absolute "Lisp" "cl-http" "cl-http-342" "server")))
(#P"/Lisp/cl-http/cl-http-342/server/md5.lisp"
 #P"/Lisp/cl-http/cl-http-342/server/md5.xfasl")

上面使用了由 MAKE-PATHNAME 创建的路径名对象。它返回所有匹配 /Lisp/cl-http/cl-http-342/server/md5.* 的文件。

这与：相同，

(directory "/Lisp/cl-http/cl-http-342/server/md5.*")

后者更短，但取决于 Unix 路径名语法。

There are basically two ways to specify pathnames:

Using strings

Strings are obviously depending on the platform: Unix syntax vs. Windows syntax for example.

"/Users/foo/bar.text"  is a valid pathname
"/Users/foo/*/foo.*"   is a valid pathname with two wildcards

You can create a pathname object from a string:

? (pathname "/Users/bar/foo.text")
#P"/Users/bar/foo.text"

The #p above assures that a pathname object (and not a string) is created, when you read it back.

? #P"/Users/bar/foo.text"
#P"/Users/bar/foo.text"

So, internally Common Lisp works with pathname objects, but it lets you use normal strings and makes pathname objects from them if needed.

When Common Lisp sees a pathname that has not all components specified (for example the directory is missing), then it fills in the components from the pathname object that is the value of the variable *DEFAULT-PATHNAME-DEFAULTS* .

With the function DESCRIBE you can look at the components of a pathname (here Clozure CL):

? (describe (pathname "/Users/bar/*.text"))
#P"/Users/bar/*.text"
Type: PATHNAME
Class: #<BUILT-IN-CLASS PATHNAME>
TYPE: (PATHNAME . #<CCL::CLASS-WRAPPER PATHNAME #x3000401D03BD>)
%PATHNAME-DIRECTORY: (:ABSOLUTE "Users" "bar")
%PATHNAME-NAME: :WILD
%PATHNAME-TYPE: "text"
%PHYSICAL-PATHNAME-VERSION: :NEWEST
%PHYSICAL-PATHNAME-DEVICE: NIL

Using the Lisp functions creating pathname objects

MAKE-PATHNAME is the function and it takes a few keyword arguments to specify the components.

Sometimes it is also useful to create a new pathname based on an existing one:

(make-pathname :name "foo" :defaults (pathname "/Users/bar/baz.text"))

If you use the function DIRECTORY it is useful to use a pathname with wildcards. DIRECTORY then will return a list of matching pathnames. The name DIRECTORY is slightly misleading, since DIRECTORY does not list the contents of a directory, but lists the matching pathnames for (usually) a pathname with wildcards. The wildcards can match a sequences of characters in components like /foo/s*c/list*.l*. There is also the wild card ** , which is used to match parts of a directory hierarchy like /foo/**/test.lisp , which matches all files test.lisp under the directory foo and its subdirectories.

(directory "/Users/foo/Lisp/**/*.lisp")

Above should return a list of all lisp files in /Users/foo/Lisp/ and all its subdirectories.

To return the .c files in a single directory use:

(directory "/Users/foo/c/src/*.c")

Note that DIRECTORY returns a list of pathname objects (not a list of strings).

? (directory
    (make-pathname
      :name "md5"
      :type :wild
      :directory '(:absolute "Lisp" "cl-http" "cl-http-342" "server")))
(#P"/Lisp/cl-http/cl-http-342/server/md5.lisp"
 #P"/Lisp/cl-http/cl-http-342/server/md5.xfasl")

Above uses a pathname object that is created by MAKE-PATHNAME. It returns all the files that match /Lisp/cl-http/cl-http-342/server/md5.* .

This is the same as:

(directory "/Lisp/cl-http/cl-http-342/server/md5.*")

which is shorter, but depends on the Unix pathname syntax.

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无所的.畏惧 2024-08-11 12:34:05

您的路径名规范是否包含通配符？ Common Lisp 的路径名一开始有点难以掌握 - 至少对我来说是......作为 CLHS 在 directory 函数上声明：

如果路径规范不是通配符，则
结果列表将包含
零个或一个元素。

为了让你的路径名包含通配符，你可以尝试 make-pathname 函数，比如

(directory (make-pathname :directory '(:absolute "srv" "hunchentoot") :name :wild :type "lisp"))

或者甚至

(directory (make-pathname :directory '(:absolute "srv" "hunchentoot") :name :wild :type :wild))

我发现了 CL-FAD 库对于处理路径名和文件系统有很大帮助。特别是，它的 list-directory 功能可能更容易使用比普通的标准目录功能。

Does your pathname specification contain a wildcard? Common Lisp's pathname stuff is somewhat hard to grasp at first - at least for me it was... As the CLHS states on the directory function:

If the pathspec is not wild, the
resulting list will contain either
zero or one elements.

In order to have your pathname include a wildcard, you might try the make-pathname function, like

(directory (make-pathname :directory '(:absolute "srv" "hunchentoot") :name :wild :type "lisp"))

Or even

(directory (make-pathname :directory '(:absolute "srv" "hunchentoot") :name :wild :type :wild))

I found the CL-FAD library a great help for dealing with pathnames and the file system. In particular, its list-directory function might be easier to use than the plain standard directory function.

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ゃ懵逼小萝莉 2024-08-11 12:34:05

实现目录列表的现代 Common Lisp 库是 IOLIB。

它的工作原理如下：

CL-USER> (iolib.os:list-directory "/etc/apt")
(#/p/"trusted.gpg~" #/p/"secring.gpg" #/p/"trustdb.gpg" #/p/"sources.list"
 #/p/"sources.list~" #/p/"apt-file.conf" #/p/"apt.conf.d" #/p/"trusted.gpg"
 #/p/"sources.list.d")

请注意，不需要尾部斜杠或通配符。它非常强大，甚至可以处理带有错误编码的 unicode 字符的文件名。

与 CL-FAD 的区别：

您获得的对象是 IOLIB 文件路径，它是 CL 路径名的替代品，它更接近底层操作系统的功能。
IOLIB 使用 CFFI 实现其例程，因此它在所有 Lisp 实现上的工作方式相同（假设 IOLIB 有操作系统的后端），这与 CL-FAD 不同，CL-FAD 试图抽象实现的 DIRECTORY 函数及其所有怪癖。
与 CL-FAD 相比，iolib 可以正确处理符号链接（CL-FAD 的一个主要问题是它在 Windows 以外的平台上几乎无法使用，恕我直言）。

The modern Common Lisp library implementing directory listing is IOLIB.

It works like this:

CL-USER> (iolib.os:list-directory "/etc/apt")
(#/p/"trusted.gpg~" #/p/"secring.gpg" #/p/"trustdb.gpg" #/p/"sources.list"
 #/p/"sources.list~" #/p/"apt-file.conf" #/p/"apt.conf.d" #/p/"trusted.gpg"
 #/p/"sources.list.d")

Note that no trailing slash or wildcards are required. It is very robust and can even process file names with incorrectly encoded unicode characters.

Differences compared to CL-FAD:

The objects you get are IOLIB file paths, a replacement for CL's pathnames which is closer what the underlying OS does.
IOLIB implements its routines using CFFI, so it works the same on all Lisp implementations (provided IOLIB has a backend for the operating system), in contrast to CL-FAD, which tries to abstract over the implementation's DIRECTORY function with all its quirks.
In contrast to CL-FAD, iolib deals correctly with symlinks (one major issue with CL-FAD that makes it virtually unusable on platforms other than Windows IMHO).

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宛菡 2024-08-11 12:34:05

为了代码片段，我将添加一个适合我的示例。我使用 osicat （类似于 cl-fad）和 str。

编辑：也可使用uiop:directory-files。 str：包含？可以通过搜索来完成。

;; searching for "ref".
(setf *data-directory* "~/books/lisp")
(remove-if-not (lambda (it)
                   (str:contains? "ref" (namestring it)))
                (osicat:list-directory *data-directory*))

(#P"~/books/lisp/common-lisp-quick-reference-clqr-a4-booklet-all.pdf"
 #P"~/books/lisp/common-lisp-quick-reference-clqr-a4-consec.pdf"
 #P"~/books/lisp/commonLisp-interactive-approach-reference-buffalo.pdf")

如果正确使用通配符，它肯定可以得到改进。不过，这是您现在可以使用的代码片段:)

参考资料：

I'll add an example that works for me, for the sake of a code snippet. I use osicat (similar to cl-fad) and str.

edit: also with uiop:directory-files. str:contains? could be done with search.

;; searching for "ref".
(setf *data-directory* "~/books/lisp")
(remove-if-not (lambda (it)
                   (str:contains? "ref" (namestring it)))
                (osicat:list-directory *data-directory*))

returns

(#P"~/books/lisp/common-lisp-quick-reference-clqr-a4-booklet-all.pdf"
 #P"~/books/lisp/common-lisp-quick-reference-clqr-a4-consec.pdf"
 #P"~/books/lisp/commonLisp-interactive-approach-reference-buffalo.pdf")

It can certainly be improved my a proper use of wildcards. However that's a snippet you can use right now : )

References:

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