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(elisp)Relative File Names

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Enter node , (file) or (file)node

Absolute and Relative File Names
--------------------------------

   All the directories in the file system form a tree starting at the
root directory.  A file name can specify all the directory names
starting from the root of the tree; then it is called an "absolute"
file name.  Or it can specify the position of the file in the tree
relative to a default directory; then it is called a "relative" file
name.  On Unix and GNU/Linux, an absolute file name starts with a slash
or a tilde (`~'), and a relative one does not.  On MS-DOS and
MS-Windows, an absolute file name starts with a slash or a backslash, or
with a drive specification `X:/', where X is the "drive letter".  The
rules on VMS are complicated.

 - Function: file-name-absolute-p filename
     This function returns `t' if file FILENAME is an absolute file
     name, `nil' otherwise.  On VMS, this function understands both
     Unix syntax and VMS syntax.

          (file-name-absolute-p "~rms/foo")
               => t
          (file-name-absolute-p "rms/foo")
               => nil
          (file-name-absolute-p "/user/rms/foo")
               => t