What Is an Absolute Pathname VS a Relative Pathname

What is an Absolute Pathname vs a Relative Pathname

You are correct in your assumption.

the relative path is the path minus the output from pwd.

the absolute path always starts from the root "/" directory.

example:

if you have just logged in you are in your home directory - /home/user - and have a file text.txt in your home directory.

the relative path is text.txt

the absolute path is /home/user/text.txt

Difference between Relative path and absolute path in javascript

What is the difference between Relative path and absolute path?

One has to be calculated with respect to another URI. The other does not.

Is there any performance issues occures for using these paths?

Nothing significant.

We will get any secure for the sites ?

No

Is there any way to converting absolute path to relative

In really simplified terms: Working from left to right, try to match the scheme, hostname, then path segments with the URI you are trying to be relative to. Stop when you have a match.

What is the difference between an absolute and a relative path?

Say you were giving directions to a spot. You have two methods you can describe getting to the location:

  • Relative to where you stand,
  • Relative to a landmark.

Both get you to the same location, but the former doesn't always work ("take a left, then a right, go through two lights then take another right" wouldn't necessarily work from the next town over, but works from where you stand). That's essentially the difference.

If you have C:\Windows\System32, that's an absolute path. If you have Windows\System32, it will only work so long as you're starting from C:\. If you start in C:\Program Files you would need a ..\ to get there correctly.

However, no matter where you are on the hard drive, C:\Windows\System32\ is a definitive way to get to that folder.

Common Lisp: relative path to absolute

Here's the final solution (based on the previous two answers):

(defun abspath
(path-string)
(uiop:unix-namestring
(uiop:merge-pathnames*
(uiop:parse-unix-namestring path-string))))

uiop:parse-unix-namestring converts the string argument to a pathname, replacing . and .. references; uiop:merge-pathnames* translates a relative pathname to absolute; uiop:unix-namestring converts the pathname back to a string.

Also, if you know for sure what kind of file the path points to, you can use either:

(uiop:unix-namestring (uiop:file-exists-p path))

or

(uiop:unix-namestring (uiop:directory-exists-p path))

because both file-exists-p and directory-exists-p return absolute pathnames (or nil, if file does not exist).

UPDATE:

Apparently in some implementations (like ManKai Common Lisp) uiop:merge-pathnames* does not prepend the directory part if the given pathname lacks ./ prefix (for example if you feed it #P"main.c" rather than #P"./main.c"). So the safer solution is:

(defun abspath
(path-string &optional (dir-name (uiop:getcwd)))
(uiop:unix-namestring
(uiop:ensure-absolute-pathname
(uiop:merge-pathnames*
(uiop:parse-unix-namestring path-string))
dir-name)))


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