common-lisp - sbcl 判断是否是符号链接(symbolic link)

Question

如何在 sbcl 中测试路径名是否为符号链接(symbolic link)？

CL-USER> (apropos "syml" )
:CLASSIFY-SYMLINKS (bound)
:RESOLVE-SYMLINKS (bound)
:SYMLINK (bound)
SB-IMPL::CLASSIFY-SYMLINKS
SB-IMPL::RESOLVE-PROBLEMATIC-SYMLINK
SB-IMPL::RESOLVE-SYMLINKS
SB-POSIX:SYMLINK (fbound)
UIOP/FILESYSTEM:*RESOLVE-SYMLINKS* (bound)
UIOP/FILESYSTEM:RESOLVE-SYMLINKS (fbound)
UIOP/FILESYSTEM:RESOLVE-SYMLINKS* (fbound)
UTIL::CLASSIFY-SYMLINKS
UTIL::SYMLINK
; No value

这些似乎都没有用。 classify-symlinks 似乎是一个关键字。

Answer 1

长话短说

(defun symlinkp (pathname)
  (sb-posix:s-islnk (sb-posix:stat-mode (sb-posix:lstat pathname))))

要回答必须首先问的问题，如何确定某物(我假设是文件描述符)是否是 posix 中的符号链接(symbolic link)。 man 2 stat 来拯救。来自联机帮助页

• lstat() is identical to stat(), except that if path is asymbolic link, then the link itself is stat-ed, not the file that it refers to.

• The following POSIX macros are defined to check the file type using the st_mode field:

• S_ISLNK(m) symbolic link? (Not in POSIX.1-1996.)