\nA little-known quirk is that the file system accepts and ignores\na drive letter in front of a UNC path.\nFor example, if you have a directory called\n \nWhy is that?\n<\/P>\n \nRewind to 1984 and the upcoming release of MS-DOS 3.1,\nwhich added networking support.\nUp to this point, all fully-qualified file specifications\nconsisted of three components:\nA drive letter, a path, and a file name.\nMany programs relied on this breakdown and did things like\n“helpfully” prepend a drive letter if it looks like you\n“forgot” one.\nFor example, if you told it to save the results to\n \n(Compare the Unix programs that “helpfully” rewrite\n \nIn order to retain compatibility with programs that\nprovided this sort of “unwanted help”,\nthe designers of the networking support in MS-DOS\ndecided to allow the strange syntax \n[Raymond is currently away; this message was pre-recorded.]\n<\/P><\/p>\n","protected":false},"excerpt":{"rendered":" A little-known quirk is that the file system accepts and ignores a drive letter in front of a UNC path. For example, if you have a directory called \\\\server\\share\\directory, you can say dir P:\\\\server\\share\\directory and the directory will be listed to the screen. The leading P: is ignored. Why is that? Rewind to 1984 and […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[2],"class_list":["post-33243","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-history"],"acf":[],"blog_post_summary":" A little-known quirk is that the file system accepts and ignores a drive letter in front of a UNC path. For example, if you have a directory called \\\\server\\share\\directory, you can say dir P:\\\\server\\share\\directory and the directory will be listed to the screen. The leading P: is ignored. Why is that? Rewind to 1984 and […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/33243","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=33243"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/33243\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=33243"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=33243"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=33243"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\\\\server\\share\\directory<\/CODE>, you can say\n<\/P>\n\ndir P:\\\\server\\share\\directory\n<\/PRE>\nand the directory will be listed to the screen.\nThe leading
P:<\/CODE> is ignored.\n<\/P>\n\\\\server\\share\\file.txt<\/CODE> it would say,\n“Oh dear, that’s not good, the user forgot the drive letter!\nI’ll put the current drive in front to make things better,”\nresulting in\nC:\\\\server\\share\\file.txt<\/CODE>.\nOther programs would prompt you with\n“Please enter a drive letter”,\nand you couldn’t say “No, there’s no drive letter, just\ntake the path and use it.”\nThey insisted on a drive letter,\nand you darn sure better give them one.\n<\/P>\n\/\/server\/volume\/file<\/CODE> as\n\/server\/volume\/file<\/CODE> because they “know”\nthat consecutive slashes collapse,\nunaware of the special exception for two leading slashes.)\n<\/P>\nC:\\\\server\\share\\directory<\/CODE>\nand treat it as if the drive letter simply weren’t there.\nSome (but not all) of this quirk of path parsing persists today.\n<\/P> \n