Ethan Benson wrote: > > On Sun, Nov 04, 2001 at 01:03:44PM +0100, sisi wrote: > > On Sat, Nov 03, 2001 at 10:45:02PM -0900, Ethan Benson wrote: > > > On Sat, Nov 03, 2001 at 09:51:49PM -0700, Chris Tillman wrote: > > > > > > > > When I found that a few months ago, dan explained that the doubled > > > > letters > > > > were supposed to come out bold. > > > > > > ummmm, since when could you have bold and other such attributes in > > > plain ascii text? > > > > isn't this what happens when you look at man pages with a text > > editor? > > no, man chmod > manchmod > > then look at in a text editor, its full of control character > sequences, but not double text like that.
Er, well, this does depend on the capabilities of the output device specified in the TERM variable, but in most cases nroff opts for overstrike (<char>^H<char>) to accomplish bold text. However, if you put the output through some other filter and or printer/output device, the result might look like the doubled or tripled letters thing. For instance, what does backspace mean to a printer, an output only device? Maybe the printer does some kind of overstrike, maybe it preprocesses the sequence and simply prints the last character, and maybe it just ignores backspaces, as some printers do, which would result in double characters like that. Most paging filters usually try to filter out overstrike stuff, I think, and the less command does unless the term capabilities specify overstrike capability, which would be unusual for a CRT-derived device, like xterm and ansi. So you would usually not see this on your xterm even though xterm does support bold. I think nroff really should use that instead these days, since _real_ CRTs are very unusual compared to xterms and ansi emulators which usually have a bold capability. So in the case above, if you edit the manchmod, you will notice N^HNA^HAM^HME^HE which will come out as NNAAMMEE on some output devices/filters that simply eat backspaces. But most xterms and paging filters will optimize this to plain old 'NAME'. When you redirect the output of man, it is not passed through a pager, so these sequences remain. But if you go man chmod | lp most printers these days will simulate typewriter overstrike bolding by printing the second character with a slight offset. a
