UNIX Version 7 Volume 2A
Contents
1. abgdezyhikImncoprstufxqw aopBydseCnOtKAUveEconpotvoxyvo ABGDEZYHIKLMNCOPRS TUFXQW ABTAEZHOIKAMNEOIIPYTY X Q2. for simulating the older roff formatters on UNIX and GCOS and for other special applications Typically you will find these packages easier to use than troff once you get beyond the most trivial operations you should always consider them first In the few cases where existing packages don t do the whole job the solution is not to write an entirely new set of troff instructions from scratch but to make small changes to adapt packages that already exist In accordance with this philosophy of letting someone else do the work the part of troff described here is only a small part of the whole although it tries to concentrate on the more useful parts In any case there is no attempt to be complete Rather the emphasis is on showing how to do simple things and how to make incremental changes to what already exists The contents of the remaining sections are 2 Point sizes and line spacing 3 Fonts and special characters 4 Indents and line length 5 Tabs 6 Local motions Drawing lines and characters 7 Strings 8 Introduction to macros 9 Titles pages and numbering 10 Number registers and arithmetic 11 Macros with arguments 12 Conditionals 13 Environments 14 Diversions Appendix Typesetter character set The troff described here is the C language version running on UNIX at Murray Hill as documented in 1 To use troff you have to prepare not only the actual text you want printed but some information t
3. tal or vertical dimensions For example 7 21 would seem obvious enough 3 inches Sorry Remember that the default units for horizontal param eters like ll are ems That s really 7 ems 2 inches and when translated into machine units it becomes zero How about ll 7i 2 Sorry still no good the 2 is 2 ems so 7i 2 is small although not zero You must use ll 7i 2u So again a safe rule is to attach a scale indicator to every number even constants For arithmetic done within a nr command there is no implication of horizontal or vertical dimension so the default units are units and 7i 2 and 7i 2u mean the same thing Thus nr Il 7i 2 J n llu does just what you want so long as you don t forget the u on the Il command 11 Macros with arguments The next step is to define macros that can change from one use to the next according to parame ters supplied as arguments To make this work we need two things first when we define the macro we have to indicate that some parts of it will be provided as arguments when the macro is called Then when the macro is called we have to provide actual argu ments to be plugged into the definition Let us illustrate by defining a macro SM that will print its argument two points smaller than the surrounding text That is the macro call SM TROFF will produce TROFF The definition of SM is de SM s 2 1 s 2 Within
4. Bell Laboratories Computing Science Technical Report 49 1976 M E Lesk Typing Documents on UNIX Bell Laboratories 1978 J R Mashey and D W Smith PWB MM Programmer s Workbench Memorandum Mac ros Bell Laboratories internal memorandum 2 3 4 5 2 1302 Appendix A Phototypesetter Character Set These characters exist in roman italic and bold To get the one on the left type the four character name on the right ff CFE fi fi fl dA ffi Fi ffl Fl ru em d4 A2 34 co de dg fm ct ag e bu sq hy In bold sq is m The following are special font characters p1 mi x mu oe di eq G gt gt lt lt E no si ap C ox pt V gr gt AS amp Ae T ua 4 da f Gs d3 pd o if V Ner c sb sp u cu M ca c Gb gt ap E mo es 4 aa 5 ga O ci bs sc dd lt dh rh t t de ae L Adb J ab L df ef 4 k to ak bv ts br Nor ul Nm These four characters also have two character names The is the apostrophe on terminals the is the other quote mark V Y ea gl These characters exist only on the special font but they do not have four character names lt gt f For greek precede the roman letter by to get the corresponding greek for example a is a
5. and so on are all legal Notice that the scale specifier i or p or m goes inside the quotes Any character can be used in place of the quotes this is also true of all other troff commands described in this section Since troff does not take within the line verti cal motions into account when figuring out where it is on the page output lines can have unexpected posi tions if the left and right ends aren t at the same vert ical position Thus v like u and d should always balance upward vertical motion in a line with the same amount in the downward direction Arbitrary horizontal motions are also available h is quite analogous to v except that the default scale factor is ems instead of line spaces As an example h 0 1i causes a backwards motion of a tenth of an inch As a practical matter consider printing the mathematical symbol gt gt The default spacing is too wide so eqn replaces this by gt h 0 3m gt to produce gt Frequently h is used with the width function w to generate motions equal to the width of some character string The construction wthing is a number equal to the width of thing in machine units 1 432 inch All troff computations are ulti mately done in these units To move horizontally the width of an x we can say h w xu As we mentioned above the default scale factor for all horizontal dimensions is m ems so here we must have the u
6. 4i 5i 6i Unfortunately the stops are left justified only as on a typewriter so lining up columns of right justified numbers can be painful If you have many numbers or if you need more complicated table lay out don t use troff directly use the tbl program described in 3 For a handful of numeric columns you can do it this way Precede every number by enough blanks to make it line up when typed nf ta li 2i 3i l tab 2 tab 3 40 tab 50 tab 60 700 tab 800 tab 900 fi Then change each leading blank into the string 0 This is a character that does not print but that has the same width as a digit When printed this will pro duce 1 2 3 40 50 60 700 800 900 It is also possible to fill up tabbed over space with some character other than blanks by setting the tab replacement character with the tc command eta 1 5i 2 51 ste ru Aru is _ Name tab Age tab produces Name Age To reset the tab replacement character to a blank use tc with no argument Lines can also be drawn with the l command described in Section 6 troff also provides a very general mechanism called fields for setting up complicated columns This is used by tbl We will not go into it in this paper 6 Local Motions Drawing lines and characters Remember Area mm and the big P in the Paternoster How are they done troff provides a host of commands for placing characters of any size at any plac
7. Jersey 07974 1 Introduction troff 1 is a text formatting program written by J F Ossanna for producing high quality printed output from the phototypesetter on the UNIX and GCOS operating systems This document is an exam ple of troff output The single most important rule of using troff is not to use it directly but through some intermediary In many ways troff resembles an assembly language a remarkably powerful and flexible one but nonetheless such that many operations must be specified at a level of detail and in a form that is too hard for most people to use effectively For two special applications there are pro grams that provide an interface to troff for the major ity of users eqn 2 provides an easy to learn language for typesetting mathematics the eqn user need know no troff whatsoever to typeset mathemat ics tbl 3 provides the same convenience for pro ducing tables of arbitrary complexity For producing straight text which may well contain mathematics or tables there are a number of macro packages that define formatting rules and operations for specific styles of documents and reduce the amount of direct contact with troff In particular the ms 4 and PWB MM 5 packages for Bell Labs internal memoranda and external papers provide most of the facilities needed for a wide range of document preparation This memo was prepared with ms There are also packages for viewgraphs
8. diverted into a macro instead of being printed and then at some convenient time the macro may be put back into the input The command di xy begins a diversion all subsequent output is collected into the macro xy until the command di with no arguments is encountered This terminates the diversion The processed text is available at any time thereafter simply by giving the command xy The vertical size of the last finished diversion is con tained in the built in number register dn As a simple example suppose we want to implement a keep release operation so that text between the commands KS and KE will not be split across a page boundary as for a figure or table Clearly when a KS is encountered we have to begin diverting the output so we can find out how big it is Then when a KE is seen we decide whether the diverted text will fit on the current page and print it either there if it fits or at the top of the next page if it doesn t So de KS start keep br start fresh line ev 1 collect in new environment fi make it filled text di XX collect in XX de KE end keep br get last partial line di end diversion Jif n dn gt n t bp bp if doesn t fit nf bring it back in no fill XX text eV return to normal environment Recall that number register nl is the current position on the output page Since output was being diverted this remains at its value w
9. important Not only does it save typing but it makes later changes much easier Suppose we decide that the paragraph indent is too small the vertical space is much too big and roman font should be forced Instead of chang ing the whole document we need only change the definition of PP to something like de PP sp 2p ti 3m ft R paragraph macro and the change takes effect everywhere we used PP is a troff command that causes the rest of the line to be ignored We use it here to add com ments to the macro definition a wise idea once definitions get complicated As another example of macros consider these two which start and end a block of offset unfilled text like most of the examples in this paper de BS Sp nf in 0 3i start indented block de BE Sp fi in 0 3i end indented block Now we can surround text like Copy to John Doe Richard Roberts Stanley Smith by the commands BS and BE and it will come out as it did above Notice that we indented by in 0 3i instead of in 0 3i This way we can nest our uses of BS and BE to get blocks within blocks If later on we decide that the indent should be 0 5i then it is only necessary to change the definitions of BS and BE not the whole paper 9 Titles Pages and Numbering This is an area where things get tougher because nothing is done for you automatically Of necessity some of this section is a cookbook to be co
10. line is to be italicized Fonts can also be changed within a line or word with the in line command f boldface text is produced by fBbold flface fR text If you want to do this so the previous font whatever it was is left undisturbed insert extra fP commands like this fBbold fP flface fP fR text fP Because only the immediately previous font is remembered you have to restore the previous font after each change or you can lose it The same is true of ps and vs when used without an argument There are other fonts available besides the standard set although you can still use only four at any given time The command fp tells troff what fonts are physically mounted on the typesetter fp 3 H says that the Helvetica font is mounted on position 3 For a complete list of fonts and what they look like see the troff manual Appropriate fp commands should appear at the beginning of your document if you do not use the standard fonts It is possible to make a document relatively independent of the actual fonts used to print it by using font numbers instead of names for example f3 and ft 3 mean whatever font is mounted at position 3 and thus work for any setting Normal settings are roman font on 1 italic on 2 bold on 3 and spe cial on 4 There is also a way to get synthetic bold fonts by overstriking letters with a slight offset Look at the bd command in 1 Special characters have four ch
11. 4 28 36 If the number after ps is not one of these legal sizes it is rounded up to the next valid value with a maximum of 36 If no number follows ps troff reverts to the previous size whatever it was troff begins with point size 10 which is usually fine This document is in 9 point The point size can also be changed in the mid dle of a line or even a word with the in line com mand s To produce UNIX runs on a PDP 11 45 type s8UNIX s10 runs on a s8PDP s1011 45 As above s should be followed by a legal point size except that sO causes the size to revert to its previous value Notice that s1011 can be understood correctly as size 10 followed by an 11 if the size is legal but not otherwise Be cautious with similar construc tions Relative size changes are also legal and useful s 2UNIX s 2 temporarily decreases the size whatever it is by two points then restores it Relative size changes have the advantage that the size difference is independent of the starting size of the document The amount of the relative change is restricted to a single digit The other parameter that determines what the type looks like is the spacing between lines which is set independently of the point size Vertical spacing is measured from the bottom of one line to the bot tom of the next The command to control vertical spacing is vs For running text it is usually best to set the vertical spacing about 20 bigger tha
12. A TROFF Tutorial Brian W Kernighan Bell Laboratories Murray Hill New Jersey 07974 ABSTRACT troff is a text formatting program for driving the Graphic Systems photo typesetter on the UNIX and GCOS operating systems This device is capable of pro ducing high quality text this paper is an example of troff output The phototypesetter itself normally runs with four fonts containing roman italic and bold letters as on this page a full greek alphabet and a substantial number of special characters and mathematical symbols Characters can be printed in a range of sizes and placed anywhere on the page troff allows the user full control over fonts sizes and character positions as well as the usual features of a formatter right margin justification automatic hyphe nation page titling and numbering and so on It also provides macros arithmetic vari ables and operations and conditional testing for complicated formatting tasks This document is an introduction to the most basic use of troff It presents just enough information to enable the user to do simple formatting tasks like making view graphs and to make incremental changes to existing packages of troff commands In most respects the UNIX formatter nroff is identical to troff so this document also serves as a tutorial on nroff August 4 1978 UNIX is a Trademark of Bell Laboratories A TROFF Tutorial Brian W Kernighan Bell Laboratories Murray Hill New
13. L is entirely analogous except that it draws a vertical line instead of horizontal 7 Strings Obviously if a paper contains a large number of occurrences of an acute accent over a letter e typing o e for each would be a great nuisance Fortunately troff provides a way in which you can store an arbitrary collection of text in a string and thereafter use the string name as a shorthand for its contents Strings are one of several troff mechan isms whose judicious use lets you type a document with less effort and organize it so that extensive for mat changes can be made with few editing changes A reference to a string is replaced by whatever text the string was defined as Strings are defined with the command ds The line ds e o e defines the string e to have the value o e String names may be either one or two charac ters long and are referred to by x for one character names or xy for two character names Thus to get t l phone given the definition of the string e as above we can say t el ephone If a string must begin with blanks define it as ds xx text The double quote signals the beginning of the definition There is no trailing quote the end of the line terminates the string A string may actually be several lines long if troff encounters a at the end of any line it is thrown away and the next line added to the current one So you can make a long string simply by
14. Protecting by an extra layer of backslashes is only needed for n which we haven t come to yet and itself Things like s f h v and so on do not need an extra backslash since they are con verted by troff to an internal code immediately upon being seen Arithmetic expressions can appear anywhere that a number is expected As a trivial example nr PS n PS 2 decrements PS by 2 Expressions can use the arith metic operators mod the relational operators gt gt lt lt and not equal and parentheses Although the arithmetic we have done so far has been straightforward more complicated things are somewhat tricky First number registers hold only integers troff arithmetic uses truncating integer divi sion just like Fortran Second in the absence of parentheses evaluation is done left to right without any operator precedence including relational opera tors Thus 1 4 3 13 becomes 1 Number registers can occur anywhere in an expression and so can scale indicators like p i m and so on but no spaces Although integer divi sion causes truncation each number and its scale indicator is converted to machine units 1 432 inch before any arithmetic is done so 1i 2u evaluates to 0 5i correctly The scale indicator u often has to appear when you wouldn t expect it in particular when arith metic is being done in a context that implies horizon
15. a macro definition the symbol n refers to the nth argument that the macro was called with Thus 1 is the string to be placed in a smaller point size when SM is called As a slightly more complicated version the following definition of SM permits optional second and third arguments that will be printed in the normal size de SM 3 s 2 1 s 2 2 Arguments not provided when the macro is called are treated as empty so SM TROFF produces TROFF while SM TROFF produces TROFF It is convenient to reverse the order of arguments because trailing punctuation is much more common than leading By the way the number of arguments that a macro was called with is available in number register The following macro BD is the one used to make the bold roman we have been using for troff command names in text It combines horizontal motions width computations and argument rearrange ment de BD amp 3 F1 1 h w 1 u 1u 1 fP 2 10 The h and w commands need no extra backslash as we discussed above The amp is there in case the argument begins with a period Two backslashes are needed with the n com mands though to protect one of them when the macro is being defined Perhaps a second example will make this clearer Consider a macro called SH which produces section headings rather like those in this paper with the sections numbered automatically and the title in b
16. aracter names beginning with and they may be inserted any where For example Atha is produced by 14 12 34 In particular greek letters are all of the form where is an upper or lower case roman letter rem iniscent of the greek Thus to get E axB gt in bare troff we have to type ES Aamu b gt if That line is unscrambled as follows S a mu b gt Gif 8 l exenrm A complete list of these special names occurs in Appendix A In eqn 2 the same effect can be achieved with the input SIGMA alpha times beta gt inf which is less concise but clearer to the uninitiated Notice that each four character name is a sin gle character as far as troff is concerned the translate command tr Gmi em is perfectly clear meaning that is to translate into Some characters are automatically translated into others grave and acute accents apos trophes become open and close single quotes the combination of is generally preferable to the double quotes Similarly a typed minus sign becomes a hyphen To print an explicit sign use To get a backslash printed use e 4 Indents and Line Lengths troff starts with a line length of 6 5 inches too wide for 8x11 paper To reset the line length use the 1 command as in ll 6i As with sp the actual length can be specified in severa
17. by using if n SH gt 1 S1 There are a handful of other conditions that can be tested with if For example is the current page even or odd Af e tl even page title Af o tl odd page title gives facing pages different titles when used inside an appropriate new page macro Two other conditions are t and n which tell you whether the formatter is troff or nroff af t troff stuff if n nroff stuff 1l Finally string comparisons may be made in an wif af string string2 stuff does stuff if string is the same as string2 The character separating the strings can be anything rea sonable that is not contained in either string The strings themselves can reference strings with argu ments with and so on 13 Environments As we mentioned there is a potential problem when going across a page boundary parameters like size and font for a page title may well be different from those in effect in the text when the page boun dary occurs troff provides a very general way to deal with this and similar situations There are three environments each of which has independently sett able versions of many of the parameters associated with processing including size font line and title lengths fill nofill mode tab stops and even partially collected lines Thus the titling problem may be readily solved by processing the main text in one environment and titles in a separate one wit
18. current page number nl for the current vertical posi tion on the page dy mo and yr for the current day month and year and s and f for the current size and font The font is a number from 1 to 4 Any of these can be used in computations like any other register but some like s and f cannot be changed with nr As an example of the use of number registers in the ms macro package 4 most significant parameters are defined in terms of the values of a handful of number registers These include the point size for text the vertical spacing and the line and title lengths To set the point size and vertical spac ing for the following paragraphs for example a user may say nr PS 9 aor VS 11 The paragraph macro PP is defined roughly as fol lows de PP ps n PS reset size avs n VSp spacing ft R font sp 0 5v half a line ti 3m This sets the font to Roman and the point size and line spacing to whatever values are stored in the number registers PS and VS Why are there two backslashes This is the eternal problem of how to quote a quote When troff originally reads the macro definition it peels off one backslash to see what s coming next To ensure that another is left in the definition when the macro is used we have to put in two backslashes in the definition If only one backslash is used point size and vertical spacing will be frozen at the time the macro is defined not when it is used
19. e You can use them to draw special char acters or to tune your output for a particular appear Most of these commands are straightforward but messy to read and tough to type correctly ance If you won t use eqn subscripts and super scripts are most easily done with the half line local motions u and d To go back up the page half a point size insert a u at the desired place to go down insert a d u and d should always be used in pairs as explained below Thus Area pr u2 d produces Area mm To make the 2 smaller bracket it with s 2 s0 Since u and d refer to the current point size be sure to put them either both inside or both outside the size changes or you will get an unbalanced vertical motion Sometimes the space given by u and d isn t the right amount The v command can be used to request an arbitrary amount of vertical motion The in line command v amount causes motion up or down the page by the amount specified in amount For example to move the P down we used in 0 6i move paragraph in Jl 0 3i shorten lines ti 0 3i move P back v 2 s36P sO v 2 ater noster qui est in caelis A minus sign causes upward motion while no sign or a plus sign means down the page Thus v 2 causes an upward vertical motion of two line spaces There are many other ways to specify the amount of motion v0 1i7 v 3p v 0 5m
20. e name of a macro not a macro call The minus sign means measure up from the bottom of the page so 1i means one inch from the bottom The wh command appears in the input outside the definition of NP typically the input would be de NP wh li NP Now what happens As text is actually being output troff keeps track of its vertical position on the page and after a line is printed within one inch from the bottom the NP macro is activated In the jar gon the wh command sets a trap at the specified place which is sprung when that point is passed NP causes a skip to the top of the next page that s what the bp was for then prints the title with the appropriate margins Why bp and sp instead of bp and sp The answer is that sp and bp like several other com mands cause a break to take place That is all the input text collected but not yet printed is flushed out as soon as possible and the next input line is guaranteed to start a new line of output If we had used sp or bp in the NP macro this would cause a break in the middle of the current output line when a new page is started The effect would be to print the left over part of that line at the top of the page fol lowed by the next input line on a new output line This is not what we want Using instead of for a command tells troff that no break is to take place the output line currently being filled should n
21. e the bp command or split the job into a footer macro invoked at the bottom margin and a header macro invoked at the top of the page These variations are left as exercises Output page numbers are computed automati cally as each page is produced starting at 1 but no numbers are printed unless you ask for them expli citly To get page numbers printed include the char acter in the tl line at the position where you want the number to appear For example tl 7 7 centers the page number inside hyphens as on this page You can set the page number at any time with either bp n which immediately starts a new page numbered n or with pnn which sets the page number for the next page but doesn t cause a skip to the new page Again bp n sets the page number to n more than its current value bp means bp 1 10 Number Registers and Arithmetic troff has a facility for doing arithmetic and for defining and using variables with numeric values called number registers Number registers like strings and macros can be useful in setting up a document so it is easy to change later And of course they serve for any sort of arithmetic computation Like strings number registers have one or two character names They are set by the nr command and are referenced anywhere by nx one character name or n xy two character name There are quite a few pre defined number registers maintained by troff among them for the
22. ember that each is just one character to troff You can make your own overstrikes with another special convention z the zero motion com mand zx suppresses the normal horizontal motion after printing the single character x so another char acter can be laid on top of it Although sizes can be changed within o it centers the characters on the widest and there can be no horizontal or vertical motions so z may be the only way to get what you want El is produced by sp 2 s8 z sq s14 z sq s22 z sq s36 sq The sp is needed to leave room for the result As another example an extra heavy semicolon that looks like 5 instead of or 4 can be constructed with a big comma and a big period above it s 6 z v 0 25m v0 25m s0 0 25m is an empirical constant A more ornate overstrike is given by the brack eting function b which piles up characters vertically centered on the current baseline Thus we can get big brackets constructing them with piled up smaller pieces UUs by typing in only this Sp b t dk db b dc df x b are cf o at rk rb troff also provides a convenient facility for drawing horizontal and vertical lines of arbitrary length with arbitrary characters I li draws a line one inch long like this The length can be followed by the character to use if the _ isn t appropriate I 0 5i draws a half inch line of dots The construction
23. end ing each line but the last with a backslash ds xx this is a very long string Strings may be defined in terms of other strings or even in terms of themselves we will dis cuss some of these possibilities later 8 Introduction to Macros Before we can go much further in troff we need to learn a bit about the macro facility In its simplest form a macro is just a shorthand notation quite similar to a string Suppose we want every paragraph to start in exactly the same way with a space and a temporary indent of two ems Sp ti 2m Then to save typing we would like to collapse these into one shorthand line a troff command like PP that would be treated by troff exactly as Sp ti 2m PP is called a macro The way we tell troff what PP means is to define it with the de command de PP Sp ti 2m The first line names the macro we used PP for paragraph and upper case so it wouldn t conflict with any name that troff might already know about The last line marks the end of the definition In between is the text which is simply inserted when ever troff sees the command or macro call PP A macro can contain any mixture of text and format ting commands The definition of PP has to precede its first use undefined macros are simply ignored Names are restricted to one or two characters Using macros for commonly occurring sequences of commands is critically
24. for machine units or the motion produced will be far too large troff is quite happy with the nested quotes by the way so long as you don t leave any out As a live example of this kind of construction all of the command names in the text like sp were done by overstriking with a slight offset The com mands for sp are Sp h w sp u h lu sp That is put out sp move left by the width of sp move right 1 unit and print sp again Of course there is a way to avoid typing that much input for each command name which we will discuss in Sec tion 11 There are also several special purpose troff commands for local motion We have already seen 0 which is an unpaddable white space of the same width as a digit Unpaddable means that it will never be widened or split across a line by line justification and filling There is also blank which is an unpaddable character the width of a space l which is half that width V which is one quarter of the width of a space and amp which has zero width This last one is useful for example in entering a text line which would otherwise begin with a The command o used like o set of characters causes up to 9 characters to be overstruck centered on the widest This is nice for accents as in syst o e ga me t o e aa l o e aa phonique which makes syst me t l phonique The accents are ga and aa or and V rem
25. h its own suitable parameters The command ev n shifts to environment n n must be 0 1 or 2 The command ev with no argu ment returns to the previous environment Environ ment names are maintained in a stack so calls for different environments may be nested and unwound consistently Suppose we say that the main text is processed in environment 0 which is where troff begins by default Then we can modify the new page macro NP to process titles in environment 1 like this de NP ev 1 shift to new environment It 6i set parameters here ft R _ps 10 any other processing ev return to previous environment It is also possible to initialize the parameters for an environment outside the NP macro but the version shown keeps all the processing in one place and is thus easier to understand and change 14 Diversions There are numerous occasions in page layout when it is necessary to store some text for a period of time without actually printing it Footnotes are the most obvious example the text of the footnote usu ally appears in the input well before the place on the page where it is to be printed is reached In fact the place where it is output normally depends on how big it is which implies that there must be a way to pro cess the footnote at least enough to decide its size without printing it troff provides a mechanism called a diversion for doing this processing Any part of the output may be
26. hat tells how you want it printed Readers who use roff will find the approach familiar For troff the text and the formatting information are often intertwined quite intimately Most commands to troff are placed on a line separate from the text itself beginning with a period one command per line For example Some text ps 14 Some more text will change the point size that is the size of the letters being printed to 14 point one point is 1 72 inch like this Some text Some more text Occasionally though something special occurs in the middle of a line to produce Area Tr 2 you have to type Area p fIr fR s8 u2 d s0 which we will explain shortly The backslash char acter is used to introduce troff commands and spe cial characters within a line of text 2 Point Sizes Line Spacing As mentioned above the command ps sets the point size One point is 1 72 inch so 6 point charac ters are at most 1 12 inch high and 36 point charac ters are inch There are 15 point sizes listed below 6 point Pack my box with five dozen liquor jugs 7 point Pack my box with five dozen liquor jugs 8 point Pack my box with five dozen liquor jugs 9 point Pack my box with five dozen liquor jugs 10 point Pack my box with five dozen liquor 11 point Pack my box with five dozen 12 point Pack my box with five dozen 14 point Pack my box with five 16 point 18 point 20 point 22 2
27. hen the diversion started dn is the amount of text in the diversion t another built in register is the distance to the next trap which we assume is at the bottom margin of the page If the diversion is large enough to go past the trap the if is satisfied and a bp is issued In either case the diverted output is then brought back with XX It is essential to bring it back in no fill mode so troff will do no further processing on it This is not the most general keep release nor is it robust in the face of all conceivable inputs but it would require more space than we have here to write it in full generality This section is not intended to ah pe teach everything about diversions but to sketch out enough that you can read existing macro packages with some comprehension Acknowledgements I am deeply indebted to J F Ossanna the author of troff for his repeated patient explanations of fine points and for his continuing willingness to adapt troff to make other uses easier I am also grateful to Jim Blinn Ted Dolotta Doug Mcllroy Mike Lesk and Joel Sturman for helpful comments on this paper References 1 J F Ossanna NROFF TROFF User s Manual Bell Laboratories Computing Science Technical Report 54 1976 B W Kernighan A System for Typesetting Mathematics User s Guide Second Edition Bell Laboratories Computing Science Technical Report 17 1977 M E Lesk TBL A Program to Format Tables
28. itions for any of the strings 12 Conditionals Suppose we want the SH macro to leave two extra inches of space just before section 1 but nowhere else The cleanest way to do that is to test inside the SH macro whether the section number is 1 and add some space if it is The if command pro vides the conditional test that we can add just before the heading line is output if n SH 1 sp 2i first section only The condition after the if can be any arith metic or logical expression If the condition is logi cally true or arithmetically greater than zero the rest of the line is treated as if it were text here a com mand If the condition is false or zero or negative the rest of the line is skipped It is possible to do more than one command if a condition is true Suppose several operations are to be done before section 1 One possibility is to define a macro S1 and invoke it if we are about to do sec tion 1 as determined by an if de S1 processing for section 1 de SH if n SH 1 S1 An alternate way is to use the extended form of the if like this if n SH 1 processing for section 1 The braces and must occur in the positions shown or you will get unexpected extra lines in your output troff also provides an if else construction which we will not go into here A condition can be negated by preceding it with we get the same effect as above but less clearly
29. l ways inches are probably the most intuitive The maximum line length provided by the typesetter is 7 5 inches by the way To use the full width you will have to reset the default physical left margin page offset which is normally slightly less than one inch from the left edge of the paper This is done by the po command po 0 sets the offset as far to the left as it will go The indent command in causes the left margin to be indented by some specified amount from the page offset If we use in to move the left margin in and Jl to move the right margin to the left we can make offset blocks of text in 0 31 ll 0 3i text to be set into a block ll 0 3i in 0 3i will create a block that looks like this Pater noster qui est in caelis sanctificetur nomen tuum adveniat regnum tuum fiat voluntas tua sicut in caelo et in terra Amen Notice the use of and to specify the amount of change These change the previous setting by the specified amount rather than just overriding it The distinction is quite important I 1i makes lines one inch longer ll 1i makes them one inch long With in Il and po the previous value is used if no argument is specified To indent a single line use the temporary indent command ti For example all paragraphs in this memo effectively begin with the command ti 3 Three of what The default unit for ti as for most horizontally
30. n the character size For example so far in this document we have used 9 on 11 that is _ps 9 vs 11p If we changed to _ps 9 vs 9p the running text would look like this After a few lines you will agree it looks a little cramped The right vertical spacing is partly a matter of taste depending on how much text you want to squeeze into a given space and partly a matter of traditional printing style By default troff uses 10 on 12 Point size and vertical spacing make a substantial difference in the amount of text per square inch This is 12 on 14 Point size and vertical spacing make a substantial difference in the amount of text per square inch For example 10 on 12 uses about twice as much space as 7 on 8 This is 6 on 7 which is even smaller It packs a lot more words per line but you can go blind trying to read it When used without arguments ps and vs revert to the previous size and vertical spacing respec tively The command sp is used to get extra vertical space Unadorned it gives you one extra blank line one vs whatever that has been set to Typically that s more or less than you want so sp can be fol lowed by information about how much space you want sp 2i means two inches of vertical space sp 2p means two points of vertical space and sp 2 means two vertical spaces two of whatever vs is set to this can also be made explicit with sp 2v t
31. old in a smaller size The use is SH Section title If the argument to a macro is to contain blanks then it must be surrounded by double quotes unlike a string where only one leading quote is permitted Here is the definition of the SH macro nr SH 0 de SH Sp 0 31 ft B nr SH n SH 1 increment number ps n PS 1 decrease PS n SH 1 number title ps n PS restore PS Sp 0 31 ft R initialize section number The section number is kept in number register SH which is incremented each time just before it is used A number register may have the same name as a macro without conflict but a string may not We used n SH instead of n SH and n PS instead of n PS If we had used n SH we would get the value of the register at the time the macro was defined not at the time it was used If that s what you want fine but not here Similarly by using n PS we get the point size at the time the macro is called As an example that does not involve numbers recall our NP macro which had a tl left center right We could make these into parameters by using instead tl We LT We CT RT so the title comes from three strings called LT CT and RT If these are empty then the title will be a blank line Normally CT would be set with some thing like ds CT to give just the page number between hyphens as on the top of this page but a user could supply private defin
32. oriented commands Il in po is ems an em is roughly the width of the letter m in the current point size Precisely a em in size p is p points Although inches are usually clearer than ems to people who don t set type for a living ems have a place they are a measure of size that is proportional to the current point size If you want to make text that keeps its proportions regardless of point size you should use ems for all dimensions Ems can be specified as scale factors directly as in ti 2 5m Lines can also be indented negatively if the indent is already positive ti 0 3i causes the next line to be moved back three tenths of an inch Thus to make a decorative initial capital we indent the whole paragraph then move the letter P back with a ti command ater noster qui est in caelis PP reitse nomen tuum adveniat regnum tuum fiat voluntas tua sicut in caelo et in terra Amen Of course there is also some trickery to make the P bigger just a s36P sO and to move it down from its normal position see the section on local motions 5 Tabs Tabs the ASCII horizontal tab character can be used to produce output in columns or to set the horizontal position of output Typically tabs are used only in unfilled text Tab stops are set by default every half inch from the current indent but can be changed by the ta command To set stops every inch for example ta li 2i 3i
33. ot be forced out before the space or new page The list of commands that cause a break is short and natural bp br ce fi nf sp in ti All others cause no break regardless of whether you use a or a If you really need a break add a br command at the appropriate place One other thing to beware of if you re changing fonts or point sizes a lot you may find that if you cross a page boundary in an unexpected font or size your titles come out in that size and font instead of what you intended Furthermore the length of a title is independent of the current line length so titles will come out at the default length of 6 5 inches unless you change it which is done with the lt com mand There are several ways to fix the problems of point sizes and fonts in titles For the simplest appli cations we can change NP to set the proper size and font for the title then restore the previous values like this de NP bp sp 0 5i ft R set title font to roman ps 10 and size to 10 point It 6i and length to 6 inches tl left center right ps revert to previous size ft P and to previous font sp 0 3i This version of NP does not work if the fields in the tl command contain size or font changes To cope with that requires troff s environment mechan ism which we will discuss in Section 13 To get a footer at the bottom of a page you can modify NP so it does some processing befor
34. pied literally until you get some experience Suppose you want a title at the top of each page saying just left top center top right top In roff one can say he left top center top right top fo left bottom center bottom right bottom to get headers and footers automatically on every page Alas this doesn t work in troff a serious hard ship for the novice Instead you have to do a lot of specification You have to say what the actual title is easy when to print it easy enough and what to do at and around the title line harder Taking these in reverse order first we define a macro NP for new page to process titles and the like at the end of one page and the beginning of the next de NP op sp 0 5i tl left top center top right top sp 0 3i To make sure we re at the top of a page we issue a begin page command bp which causes a skip to top of page we ll explain the shortly Then we space down half an inch print the title the use of tl should be self explanatory later we will discuss parameterizing the titles space another 0 3 inches and we re done To ask for NP at the bottom of each page we have to say something like when the text is within an inch of the bottom of the page start the processing for a new page This is done with a when com mand wh wh li NP No is used before NP this is simply th
35. roff also understands decimal fractions in most places so sp 1 51 is a space of 1 5 inches These same scale factors can be used after vs to define line spacing and in fact after most commands that deal with physical dimensions It should be noted that all size numbers are converted internally to machine units which are 1 432 inch 1 6 point For most purposes this is enough resolution that you don t have to worry about the accuracy of the representation The situation is not quite so good vertically where resolution is 1 144 inch 1 2 point 3 Fonts and Special Characters troff and the typesetter allow four different fonts at any one time Normally three fonts Times roman italic and bold and one collection of special characters are permanently mounted abcdefghijklmnopqrstuvwxyz 0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz 0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz 0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZ The greek mathematical symbols and miscellany of the special font are listed in Appendix A troff prints in roman unless told otherwise To switch into bold use the ft command ft B and for italics ft I To return to roman use ft R to return to the previ ous font whatever it was use either ft P or just ft The underline command ul causes the next input line to print in italics ul can be followed by a count to indicate that more than one
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