A quotation mark mystery explained

For many years I've been mystified about the curiously rampant misuse of grave accents in Unix software and documentation. I'm aware of their use as backticks for substitution, e.g. in bash and Perl; an occasionally unsafe but not in itself offensive idiom. No, what I'm referring to here is this kind of abuse (from the GNU ln manual page):

There are two concepts of `link' in Unix, usually called hard link and soft link. A hard link is just a name for a file. (And a file can have several names. It is deleted from disk only when the last name is removed. The number of names is given by ls(1). There is no such thing as an `original' name: all names have the same status. Usually, but not necessarily, all names of a file are found in the filesystem that also contains its data.)

Note how the words link and original have been prefixed with grave accents and suffixed by apostrophes. I'm confident that the author's (arguably gratuitous) intention was for those words to be surrounded by quotation marks. Why use this inappropriate and ugly pair of characters rather than quotation marks (or apostrophes only, to approximate single quotation marks in ASCII)? I could see no reason and the same eccentric style could be found in too many places for me to dismiss it as the work of a single confused author.

My previous, admittedly rather cursory investigation into this matter resulted in several leads but no plausible explanation. I found many claims that the characters were used as directional quotation marks (i.e. differentiated opening and closing marks) and that the origin was Donald Knuth's typesetting system TeX, in which backticks and apostrophes may be used to encode this typographical subtlety.

I did not feel my quotation question adequately answered by this; grave accents and apostrophes do not look even remotely like directional quotation marks, and unlike (formatted) man pages and error messages TeX code is not meant for the end user to read. It's supposed to be processed into a format suited for printing or viewing on a screen, with real quotation marks (directional if possible). I'm certainly not in the habit of piping program error messages through TeX, how about you? Besides, the quoting style recognized by TeX also involves two successive backticks and apostrophes while the mysterious Unix style usually has only one of each.

This blatant character abuse had been ticking me off for a long time when I stumbled upon an excellent explanation written by Markus Kuhn, who finally provided me with a satisfactory answer. Apparently there was an early ASCII version which defined the codes now corresponding to apostrophe and grave accent as multiple characters, including single quotation marks. Consequently the glyphs for those two codes in X fonts were designed to resemble several different characters. Taken together, the glyphs did look similar to directional single quotation marks and people used them as such.

According to Mr. Kuhn, this had not been fixed in the X fonts until last year! I can't remember ever seeing the old glyphs, but I suppose that could be because I change fonts from the default ones. I'll still be annoyed whenever I see those characters used incorrectly, but now I know why people do it.

9 July, 2005