This is groff, produced by makeinfo version 4.3d from ./groff.texinfo. This manual documents GNU `troff' version 1.19. Copyright (C) 1994-2000, 2001, 2002, 2003 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover texts being `A GNU Manual," and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled `GNU Free Documentation License." (a) The FSF's Back-Cover Text is: `You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development." INFO-DIR-SECTION Typesetting START-INFO-DIR-ENTRY * Groff: (groff). The GNU troff document formatting system. END-INFO-DIR-ENTRY  File: groff, Node: Page Location Traps, Next: Diversion Traps, Prev: Traps, Up: Traps Page Location Traps ------------------- "Page location traps" perform an action when `gtroff' reaches or passes a certain vertical location on the page. Page location traps have a variety of purposes, including: * setting headers and footers * setting body text in multiple columns * setting footnotes - Request: .vpt flag - Register: \n[.vpt] Enable vertical position traps if FLAG is non-zero, or disables them otherwise. Vertical position traps are traps set by the `wh' or `dt' requests. Traps set by the `it' request are not vertical position traps. The parameter that controls whether vertical position traps are enabled is global. Initially vertical position traps are enabled. The current setting of this is available in the `.vpt' read-only number register. Note that a page can't be ejected if `vpt' is set to zero. - Request: .wh dist [macro] Set a page location trap. Non-negative values for DIST set the trap relative to the top of the page; negative values set the trap relative to the bottom of the page. Default scaling indicator is `v'. MACRO is the name of the macro to execute when the trap is sprung. If MACRO is missing, remove the first trap (if any) at DIST. The following is a simple example of how many macro packages set headers and footers. .de hd \" Page header ' sp .5i . tl 'Title''date' ' sp .3i .. . .de fo \" Page footer ' sp 1v . tl ''%'' ' bp .. . .wh 0 hd \" trap at top of the page .wh -1i fo \" trap one inch from bottom A trap at or below the bottom of the page is ignored; it can be made active by either moving it up or increasing the page length so that the trap is on the page. It is possible to have more than one trap at the same location; to do so, the traps must be defined at different locations, then moved together with the `ch' request; otherwise the second trap would replace the first one. Earlier defined traps hide later defined traps if moved to the same position (the many empty lines caused by the `bp' request are omitted in the following example): .de a . nop a .. .de b . nop b .. .de c . nop c .. . .wh 1i a .wh 2i b .wh 3i c .bp => a b c .ch b 1i .ch c 1i .bp => a .ch a 0.5i .bp => a b - Register: \n[.t] A read-only number register holding the distance to the next trap. If there are no traps between the current position and the bottom of the page, it contains the distance to the page bottom. In a diversion, the distance to the page bottom is infinite (the returned value is the biggest integer which can be represented in `groff') if there are no diversion traps. - Request: .ch macro [dist] Change the location of a trap. The first argument is the name of the macro to be invoked at the trap, and the second argument is the new location for the trap (note that the parameters are specified in opposite order as in the `wh' request). This is useful for building up footnotes in a diversion to allow more space at the bottom of the page for them. Default scaling indicator for DIST is `v'. If DIST is missing, the trap is removed. - Register: \n[.ne] The read-only number register `.ne' contains the amount of space that was needed in the last `ne' request that caused a trap to be sprung. Useful in conjunction with the `.trunc' register. *Note Page Control::, for more information. Since the `.ne' register is only set by traps it doesn't make much sense to use it outside of trap macros. - Register: \n[.trunc] A read-only register containing the amount of vertical space truncated by the most recently sprung vertical position trap, or, if the trap was sprung by an `ne' request, minus the amount of vertical motion produced by the `ne' request. In other words, at the point a trap is sprung, it represents the difference of what the vertical position would have been but for the trap, and what the vertical position actually is. Since the `.trunc' register is only set by traps and it doesn't make much sense to use it outside of trap macros. - Register: \n[.pe] A read-only register which is set to 1 while a page is ejected with the `bp' request (or by the end of input). Outside of traps this register is always zero. In the following example, only the second call to `x' is caused by `bp'. .de x \&.pe=\\n[.pe] .br .. .wh 1v x .wh 4v x A line. .br Another line. .br => A line. .pe=0 Another line. .pe=1 An important fact to consider while designing macros is that diversions and traps do not interact normally. For example, if a trap invokes a header macro (while outputting a diversion) which tries to change the font on the current page, the effect will not be visible before the diversion has completely been printed (except for input protected with `\!' or `\?') since the data in the diversion is already formatted. In most cases, this is not the expected behaviour.  File: groff, Node: Diversion Traps, Next: Input Line Traps, Prev: Page Location Traps, Up: Traps Diversion Traps --------------- - Request: .dt dist macro Set a trap _within_ a diversion. DIST is the location of the trap (identical to the `wh' request; default scaling indicator is `v') and MACRO is the name of the macro to be invoked. The number register `.t' still works within diversions. *Note Diversions::, for more information.  File: groff, Node: Input Line Traps, Next: Blank Line Traps, Prev: Diversion Traps, Up: Traps Input Line Traps ---------------- - Request: .it n macro - Request: .itc n macro Set an input line trap. N is the number of lines of input which may be read before springing the trap, MACRO is the macro to be invoked. Request lines are not counted as input lines. For example, one possible use is to have a macro which prints the next N lines in a bold font. .de B . it \\$1 B-end . ft B .. . .de B-end . ft R .. The `itc' request is identical except that an interrupted text line (ending with `\c') is not counted as a separate line. Both requests are associated with the current environment (*note Environments::); switching to another environment disables the current input trap, and going back reactivates it, restoring the number of already processed lines.  File: groff, Node: Blank Line Traps, Next: End-of-input Traps, Prev: Input Line Traps, Up: Traps Blank Line Traps ---------------- - Request: .blm macro Set a blank line trap. `gtroff' executes MACRO when it encounters a blank line in the input file.  File: groff, Node: End-of-input Traps, Prev: Blank Line Traps, Up: Traps End-of-input Traps ------------------ - Request: .em macro Set a trap at the end of input. MACRO is executed after the last line of the input file has been processed. For example, if the document had to have a section at the bottom of the last page for someone to approve it, the `em' request could be used. .de approval . ne 5v . sp |(\\n[.t] - 6v) . in +4i . lc _ . br Approved:\t\a . sp Date:\t\t\a .. . .em approval  File: groff, Node: Diversions, Next: Environments, Prev: Traps, Up: gtroff Reference Diversions ========== In `gtroff' it is possible to "divert" text into a named storage area. Due to the similarity to defining macros it is sometimes said to be stored in a macro. This is used for saving text for output at a later time, which is useful for keeping blocks of text on the same page, footnotes, tables of contents, and indices. For orthogonality it is said that `gtroff' is in the "top-level diversion" if no diversion is active (i.e., the data is diverted to the output device). - Request: .di macro - Request: .da macro Begin a diversion. Like the `de' request, it takes an argument of a macro name to divert subsequent text into. The `da' macro appends to an existing diversion. `di' or `da' without an argument ends the diversion. - Request: .box macro - Request: .boxa macro Begin (or appends to) a diversion like the `di' and `da' requests. The difference is that `box' and `boxa' do not include a partially-filled line in the diversion. Compare this: Before the box. .box xxx In the box. .br .box After the box. .br => Before the box. After the box. .xxx => In the box. with this: Before the diversion. .di yyy In the diversion. .br .di After the diversion. .br => After the diversion. .yyy => Before the diversion. In the diversion. `box' or `boxa' without an argument ends the diversion. - Register: \n[.z] - Register: \n[.d] Diversions may be nested. The read-only number register `.z' contains the name of the current diversion (this is a string-valued register). The read-only number register `.d' contains the current vertical place in the diversion. If not in a diversion it is the same as register `nl'. - Register: \n[.h] The "high-water mark" on the current page. It corresponds to the text baseline of the lowest line on the page. This is a read-only register. .tm .h==\n[.h], nl==\n[nl] => .h==0, nl==-1 This is a test. .br .sp 2 .tm .h==\n[.h], nl==\n[nl] => .h==40, nl==120 As can be seen in the previous example, empty lines are not considered in the return value of the `.h' register. - Register: \n[dn] - Register: \n[dl] After completing a diversion, the read-write number registers `dn' and `dl' contain the vertical and horizontal size of the diversion. Note that only the just processed lines are counted: For the computation of `dn' and `dl', the requests `da' and `boxa' are handled as if `di' and `box' had been used - lines which have been already stored in a macro are not taken into account. .\" Center text both horizontally & vertically . .\" Enclose macro definitions in .eo and .ec .\" to avoid the doubling of the backslash .eo .\" macro .(c starts centering mode .de (c . br . ev (c . evc 0 . in 0 . nf . di @c .. .\" macro .)c terminates centering mode .de )c . br . ev . di . nr @s (((\n[.t]u - \n[dn]u) / 2u) - 1v) . sp \n[@s]u . ce 1000 . @c . ce 0 . sp \n[@s]u . br . fi . rr @s . rm @s . rm @c .. .\" End of macro definitions, restore escape mechanism .ec - Escape: \! - Escape: \?anything\? Prevent requests, macros, and escapes from being interpreted when read into a diversion. Both escapes take the given text and "transparently" embed it into the diversion. This is useful for macros which shouldn't be invoked until the diverted text is actually output. The `\!' escape transparently embeds text up to and including the end of the line. The `\?' escape transparently embeds text until the next occurrence of the `\?' escape. Example: \?ANYTHING\? ANYTHING may not contain newlines; use `\!' to embed newlines in a diversion. The escape sequence `\?' is also recognized in copy mode and turned into a single internal code; it is this code that terminates ANYTHING. Thus the following example prints 4. .nr x 1 .nf .di d \?\\?\\\\?\\\\\\\\nx\\\\?\\?\? .di .nr x 2 .di e .d .di .nr x 3 .di f .e .di .nr x 4 .f Both escapes read the data in copy mode. If `\!' is used in the top-level diversion, its argument is directly embedded into the `gtroff' intermediate output. This can be used for example to control a postprocessor which processes the data before it is sent to the device driver. The `\?' escape used in the top-level diversion produces no output at all; its argument is simply ignored. - Request: .output string Emit STRING directly to the `gtroff' intermediate output (subject to copy-mode interpretation); this is similar to `\!' used at the top level. An initial double quote in STRING is stripped off to allow initial blanks. This request can't be used before the first page has started - if you get an error, simply insert `.br' before the `output' request. Without argument, `output' is ignored. Use with caution! It is normally only needed for mark-up used by a postprocessor which does something with the output before sending it to the output device, filtering out STRING again. - Request: .asciify div "Unformat" the diversion specified by DIV in such a way that ASCII characters, characters translated with the `trin' request, space characters, and some escape sequences that were formatted and diverted are treated like ordinary input characters when the diversion is reread. It can be also used for gross hacks; for example, the following sets register `n' to 1. .tr @. .di x @nr n 1 .br .di .tr @@ .asciify x .x *Note Copy-in Mode::. - Request: .unformat div Like `asciify', unformat the specified diversion. However, `unformat' only unformats spaces and tabs between words. Unformatted tabs are treated as input tokens, and spaces are stretchable again. The vertical size of lines is not preserved; glyph information (font, font size, space width, etc.) is retained.  File: groff, Node: Environments, Next: Suppressing output, Prev: Diversions, Up: gtroff Reference Environments ============ It happens frequently that some text should be printed in a certain format regardless of what may be in effect at the time, for example, in a trap invoked macro to print headers and footers. To solve this `gtroff' processes text in "environments". An environment contains most of the parameters that control text processing. It is possible to switch amongst these environments; by default `gtroff' processes text in environment 0. The following is the information kept in an environment. * font parameters (size, family, style, glyph height and slant, space and sentence space size) * page parameters (line length, title length, vertical spacing, line spacing, indentation, line numbering, centering, right-justifying, underlining, hyphenation data) * fill and adjust mode * tab stops, tab and leader characters, escape character, no-break and hyphen indicators, margin character data * partially collected lines * input traps * drawing and fill colours These environments may be given arbitrary names (see *Note Identifiers::, for more info). Old versions of `troff' only had environments named `0', `1', and `2'. - Request: .ev [env] - Register: \n[.ev] Switch to another environment. The argument ENV is the name of the environment to switch to. With no argument, `gtroff' switches back to the previous environment. There is no limit on the number of named environments; they are created the first time that they are referenced. The `.ev' read-only register contains the name or number of the current environment. This is a string-valued register. Note that a call to `ev' (with argument) pushes the previously active environment onto a stack. If, say, environments `foo', `bar', and `zap' are called (in that order), the first `ev' request without parameter switches back to environment `bar' (which is popped off the stack), and a second call switches back to environment `foo'. Here is an example: .ev footnote-env .fam N .ps 6 .vs 8 .ll -.5i .ev ... .ev footnote-env \(dg Note the large, friendly letters. .ev - Request: .evc env Copy the environment ENV into the current environment. The following environment data is not copied: * Partially filled lines. * The status whether the previous line was interrupted. * The number of lines still to center, or to right-justify, or to underline (with or without underlined spaces); they are set to zero. * The status whether a temporary indent is active. * Input traps and its associated data. * Line numbering mode is disabled; it can be reactivated with `.nm +0'. * The number of consecutive hyphenated lines (set to zero). - Register: \n[.w] - Register: \n[.cht] - Register: \n[.cdp] - Register: \n[.csk] The `\n[.w]' register contains the width of the last glyph added to the current environment. The `\n[.cht]' register contains the height of the last glyph added to the current environment. The `\n[.cdp]' register contains the depth of the last glyph added to the current environment. It is positive for glyphs extending below the baseline. The `\n[.csk]' register contains the "skew" (how far to the right of the glyph's center that `gtroff' should place an accent) of the last glyph added to the current environment. - Register: \n[.n] The `\n[.n]' register contains the length of the previous output line in the current environment.  File: groff, Node: Suppressing output, Next: Colors, Prev: Environments, Up: gtroff Reference Suppressing output ================== - Escape: \Onum Disable or enable output depending on the value of NUM: `\O0' Disable any glyphs from being emitted to the device driver, provided that the escape occurs at the outer level (see `\O[3]' and `\O[4]'). Motion is not suppressed so effectively `\O[0]' means _pen up_. `\O1' Enable output of glyphs, provided that the escape occurs at the outer level. `\O0' and `\O1' also reset the four registers `opminx', `opminy', `opmaxx', and `opmaxy' to -1. *Note Register Index::. These four registers mark the top left and bottom right hand corners of a box which encompasses all written glyphs. For example the input text: Hello \O[0]world \O[1]this is a test. produces the following output: Hello this is a test. `\O2' Provided that the escape occurs at the outer level, enable output of glyphs and also write out to `stderr' the page number and four registers encompassing the glyphs previously written since the last call to `\O'. `\O3' Begin a nesting level. At start-up, `gtroff' is at outer level. `\O4' End a nesting level. `\O[5PFILENAME]' This escape is `grohtml' specific. Provided that this escape occurs at the outer nesting level write the `filename' to `stderr'. The position of the image, P, must be specified and must be one of `l', `r', `c', or `i' (left, right, centered, inline). FILENAME will be associated with the production of the next inline image.  File: groff, Node: Colors, Next: I/O, Prev: Suppressing output, Up: gtroff Reference Colors ====== - Request: .color [n] - Register: \n[.color] If N is missing or non-zero, activate colors (this is the default); otherwise, turn it off. The read-only number register `.color' is 1 if colors are active, 0 otherwise. Internally, `color' sets a global flag; it does not produce a token. Similar to the `cp' request, you should use it at the beginning of your document to control color output. Colors can be also turned off with the `-c' command line option. - Request: .defcolor ident scheme color_components Define color with name IDENT. SCHEME can be one of the following values: `rgb' (three components), `cmy' (three components), `cmyk' (four components), and `gray' or `grey' (one component). Color components can be given either as a hexadecimal string or as positive decimal integers in the range 0-65535. A hexadecimal string contains all color components concatenated. It must start with either `#' or `##'; the former specifies hex values in the range 0-255 (which are internally multiplied by 257), the latter in the range 0-65535. Examples: `#FFC0CB' (pink), `##ffff0000ffff' (magenta). The default color name value is device-specific (usually black). It is possible that the default color for `\m' and `\M' is not identical. A new scaling indicator `f' has been introduced which multiplies its value by 65536; this makes it convenient to specify color components as fractions in the range 0 to 1 (1f equals 65536u). Example: .defcolor darkgreen rgb 0.1f 0.5f 0.2f Note that `f' is the default scaling indicator for the `defcolor' request, thus the above statement is equivalent to .defcolor darkgreen rgb 0.1 0.5 0.2 - Escape: \mc - Escape: \m(co - Escape: \m[color] Set drawing color. The following example shows how to turn the next four words red. \m[red]these are in red\m[] and these words are in black. The escape `\m[]' returns to the previous color. The drawing color is associated with the current environment (*note Environments::). Note that `\m' doesn't produce an input token in `gtroff'. As a consequence, it can be used in requests like `mc' (which expects a single character as an argument) to change the color on the fly: .mc \m[red]x\m[] - Escape: \Mc - Escape: \M(co - Escape: \M[color] Set background color for filled objects drawn with the `\D'...'' commands. A red ellipse can be created with the following code: \M[red]\h'0.5i'\D'E 2i 1i'\M[] The escape `\M[]' returns to the previous fill color. The fill color is associated with the current environment (*note Environments::). Note that `\M' doesn't produce an input token in `gtroff'.  File: groff, Node: I/O, Next: Postprocessor Access, Prev: Colors, Up: gtroff Reference I/O === `gtroff' has several requests for including files: - Request: .so file Read in the specified FILE and includes it in place of the `so' request. This is quite useful for large documents, e.g. keeping each chapter in a separate file. *Note gsoelim::, for more information. Since `gtroff' replaces the `so' request with the contents of `file', it makes a difference whether the data is terminated with a newline or not: Assuming that file `xxx' contains the word `foo' without a final newline, this This is .so xxx bar yields `This is foobar'. - Request: .pso command Read the standard output from the specified COMMAND and includes it in place of the `pso' request. This request causes an error if used in safer mode (which is the default). Use `groff''s or `troff''s `-U' option to activate unsafe mode. The comment regarding a final newline for the `so' request is valid for `pso' also. - Request: .mso file Identical to the `so' request except that `gtroff' searches for the specified FILE in the same directories as macro files for the the `-m' command line option. If the file name to be included has the form `NAME.tmac' and it isn't found, `mso' tries to include `tmac.NAME' and vice versa. - Request: .trf file - Request: .cf file Transparently output the contents of FILE. Each line is output as if it were preceded by `\!'; however, the lines are not subject to copy mode interpretation. If the file does not end with a newline, then a newline is added (`trf' only). For example, to define a macro `x' containing the contents of file `f', use .di x .trf f .di Both `trf' and `cf', when used in a diversion, embeds an object in the diversion which, when reread, causes the contents of FILE to be transparently copied through to the output. In UNIX `troff', the contents of FILE is immediately copied through to the output regardless of whether there is a current diversion; this behaviour is so anomalous that it must be considered a bug. While `cf' copies the contents of FILE completely unprocessed, `trf' disallows characters such as NUL that are not valid `gtroff' input characters (*note Identifiers::). Both requests cause a line break. - Request: .nx [file] Force `gtroff' to continue processing of the file specified as an argument. If no argument is given, immediately jump to the end of file. - Request: .rd [prompt [arg1 arg2 ...]] Read from standard input, and include what is read as though it were part of the input file. Text is read until a blank line is encountered. If standard input is a TTY input device (keyboard), write PROMPT to standard error, followed by a colon (or send BEL for a beep if no argument is given). Arguments after PROMPT are available for the input. For example, the line .rd data foo bar with the input `This is \$2.' prints This is bar. Using the `nx' and `rd' requests, it is easy to set up form letters. The form letter template is constructed like this, putting the following lines into a file called `repeat.let': .ce \*(td .sp 2 .nf .rd .sp .rd .fi Body of letter. .bp .nx repeat.let When this is run, a file containing the following lines should be redirected in. Note that requests included in this file are executed as though they were part of the form letter. The last block of input is the `ex' request which tells `groff' to stop processing. If this was not there, `groff' would not know when to stop. Trent A. Fisher 708 NW 19th Av., #202 Portland, OR 97209 Dear Trent, Len Adollar 4315 Sierra Vista San Diego, CA 92103 Dear Mr. Adollar, .ex - Request: .pi pipe Pipe the output of `gtroff' to the shell command(s) specified by PIPE. This request must occur before `gtroff' has a chance to print anything. `pi' causes an error if used in safer mode (which is the default). Use `groff''s or `troff''s `-U' option to activate unsafe mode. Multiple calls to `pi' are allowed, acting as a chain. For example, .pi foo .pi bar ... is the same as `.pi foo | bar'. Note that the intermediate output format of `gtroff' is piped to the specified commands. Consequently, calling `groff' without the `-Z' option normally causes a fatal error. - Request: .sy cmds - Register: \n[systat] Execute the shell command(s) specified by CMDS. The output is not saved anyplace, so it is up to the user to do so. This request causes an error if used in safer mode (which is the default). Use `groff''s or `troff''s `-U' option to activate unsafe mode. For example, the following code fragment introduces the current time into a document: .sy perl -e 'printf ".nr H %d\\n.nr M %d\\n.nr S %d\\n",\ (localtime(time))[2,1,0]' > /tmp/x\n[$$] .so /tmp/x\n[$$] .sy rm /tmp/x\n[$$] \nH:\nM:\nS Note that this works by having the `perl' script (run by `sy') print out the `nr' requests which set the number registers `H', `M', and `S', and then reads those commands in with the `so' request. For most practical purposes, the number registers `seconds', `minutes', and `hours' which are initialized at start-up of `gtroff' should be sufficient. Use the `af' request to get a formatted output: .af hours 00 .af minutes 00 .af seconds 00 \n[hours]:\n[minutes]:\n[seconds] The `systat' read-write number register contains the return value of the `system()' function executed by the last `sy' request. - Request: .open stream file - Request: .opena stream file Open the specified FILE for writing and associates the specified STREAM with it. The `opena' request is like `open', but if the file exists, append to it instead of truncating it. Both `open' and `opena' cause an error if used in safer mode (which is the default). Use `groff''s or `troff''s `-U' option to activate unsafe mode. - Request: .write stream data - Request: .writec stream data Write to the file associated with the specified STREAM. The stream must previously have been the subject of an open request. The remainder of the line is interpreted as the `ds' request reads its second argument: A leading `"' is stripped, and it is read in copy-in mode. The `writec' request is like `write', but only `write' appends a newline to the data. - Request: .writem stream xx Write the contents of the macro or string XX to the file associated with the specified STREAM. XX is read in copy mode, i.e., already formatted elements are ignored. Consequently, diversions must be unformatted with the `asciify' request before calling `writem'. Usually, this means a loss of information. - Request: .close stream Close the specified STREAM; the stream is no longer an acceptable argument to the `write' request. Here a simple macro to write an index entry. .open idx test.idx . .de IX . write idx \\n[%] \\$* .. . .IX test entry . .close idx - Escape: \Ve - Escape: \V(ev - Escape: \V[env] Interpolate the contents of the specified environment variable ENV (one-character name E, two-character name EV) as returned by the function `getenv'. `\V' is interpreted in copy-in mode.  File: groff, Node: Postprocessor Access, Next: Miscellaneous, Prev: I/O, Up: gtroff Reference Postprocessor Access ==================== There are two escapes which give information directly to the postprocessor. This is particularly useful for embedding POSTSCRIPT into the final document. - Escape: \X'xxx' Embeds its argument into the `gtroff' output preceded with `x X'. The escapes `\&', `\)', `\%', and `\:' are ignored within `\X', `\ ' and `\~' are converted to single space characters. All other escapes (except `\\' which produces a backslash) cause an error. If the `use_charnames_in_special' keyword is set in the `DESC' file, special characters no longer cause an error; the name XX is represented as `\(XX)' in the `x X' output command. Additionally, the backslash is represented as `\\'. `use_charnames_in_special' is currently used by `grohtml' only. - Escape: \Yn - Escape: \Y(nm - Escape: \Y[name] This is approximately equivalent to `\X'\*[NAME]'' (one-character name N, two-character name NM). However, the contents of the string or macro NAME are not interpreted; also it is permitted for NAME to have been defined as a macro and thus contain newlines (it is not permitted for the argument to `\X' to contain newlines). The inclusion of newlines requires an extension to the UNIX `troff' output format, and confuses drivers that do not know about this extension (*note Device Control Commands::). *Note Output Devices::.  File: groff, Node: Miscellaneous, Next: Gtroff Internals, Prev: Postprocessor Access, Up: gtroff Reference Miscellaneous ============= This section documents parts of `gtroff' which cannot (yet) be categorized elsewhere in this manual. - Request: .nm [start [inc [space [indent]]]] Print line numbers. START is the line number of the _next_ output line. INC indicates which line numbers are printed. For example, the value 5 means to emit only line numbers which are multiples of 5; this defaults to 1. SPACE is the space to be left between the number and the text; this defaults to one digit space. The fourth argument is the indentation of the line numbers, defaulting to zero. Both SPACE and INDENT are given as multiples of digit spaces; they can be negative also. Without any arguments, line numbers are turned off. `gtroff' reserves three digit spaces for the line number (which is printed right-justified) plus the amount given by INDENT; the output lines are concatenated to the line numbers, separated by SPACE, and _without_ reducing the line length. Depending on the value of the horizontal page offset (as set with the `po' request), line numbers which are longer than the reserved space stick out to the left, or the whole line is moved to the right. Parameters corresponding to missing arguments are not changed; any non-digit argument (to be more precise, any argument starting with a character valid as a delimiter for identifiers) is also treated as missing. If line numbering has been disabled with a call to `nm' without an argument, it can be reactivated with `.nm +0', using the previously active line numbering parameters. The parameters of `nm' are associated with the current environment (*note Environments::). The current output line number is available in the number register `ln'. .po 1m .ll 2i This test shows how line numbering works with groff. .nm 999 This test shows how line numbering works with groff. .br .nm xxx 3 2 .ll -\w'0'u This test shows how line numbering works with groff. .nn 2 This test shows how line numbering works with groff. And here the result: This test shows how line numbering works 999 with groff. This 1000 test shows how line 1001 numbering works with 1002 groff. This test shows how line numbering works with groff. This test shows how 1005 line numbering works with groff. - Request: .nn [skip] Temporarily turn off line numbering. The argument is the number of lines not to be numbered; this defaults to 1. - Request: .mc glyph [dist] Print a "margin character" to the right of the text.(1) (*note Miscellaneous-Footnote-1::) The first argument is the glyph to be printed. The second argument is the distance away from the right margin. If missing, the previously set value is used; default is 10pt). For text lines that are too long (that is, longer than the text length plus DIST), the margin character is directly appended to the lines. With no arguments the margin character is turned off. If this occurs before a break, no margin character is printed. For empty lines and lines produced by the `tl' request no margin character is emitted. The margin character is associated with the current environment (*note Environments::). This is quite useful for indicating text that has changed, and, in fact, there are programs available for doing this (they are called `nrchbar' and `changebar' and can be found in any `comp.sources.unix' archive. .ll 3i .mc | This paragraph is highlighted with a margin character. .sp Note that vertical space isn't marked. .br \& .br But we can fake it with `\&'. Result: This paragraph is highlighted | with a margin character. | Note that vertical space isn't | marked. | | But we can fake it with `\&'. | - Request: .psbb filename - Register: \n[llx] - Register: \n[lly] - Register: \n[urx] - Register: \n[ury] Retrieve the bounding box of the PostScript image found in FILENAME. The file must conform to Adobe's "Document Structuring Conventions" (DSC); the command searches for a `%%BoundingBox' comment and extracts the bounding box values into the number registers `llx', `lly', `urx', and `ury'. If an error occurs (for example, `psbb' cannot find the `%%BoundingBox' comment), it sets the four number registers to zero.  File: groff, Node: Miscellaneous-Footnotes, Up: Miscellaneous (1) "Margin character" is a misnomer since it is an output glyph.  File: groff, Node: Gtroff Internals, Next: Debugging, Prev: Miscellaneous, Up: gtroff Reference `gtroff' Internals ================== `gtroff' processes input in three steps. One or more input characters are converted to an "input token".(1) (*note Gtroff Internals-Footnote-1::) Then, one or more input tokens are converted to an "output node". Finally, output nodes are converted to the intermediate output language understood by all output devices. Actually, before step one happens, `gtroff' converts certain escape sequences into reserved input characters (not accessible by the user); such reserved characters are used for other internal processing also - this is the very reason why not all characters are valid input. *Note Identifiers::, for more on this topic. For example, the input string `fi\[:u]' is converted into a character token `f', a character token `i', and a special token `:u' (representing u umlaut). Later on, the character tokens `f' and `i' are merged to a single output node representing the ligature glyph `fi' (provided the current font has a glyph for this ligature); the same happens with `:u'. All output glyph nodes are `processed' which means that they are invariably associated with a given font, font size, advance width, etc. During the formatting process, `gtroff' itself adds various nodes to control the data flow. Macros, diversions, and strings collect elements in two chained lists: a list of input tokens which have been passed unprocessed, and a list of output nodes. Consider the following the diversion. .di xxx a \!b c .br .di It contains these elements. node list token list element number line start node -- 1 glyph node `a' -- 2 word space node -- 3 -- `b' 4 -- `\n' 5 glyph node `c' -- 6 vertical size node -- 7 vertical size node -- 8 -- `\n' 9 Elements 1, 7, and 8 are inserted by `gtroff'; the latter two (which are always present) specify the vertical extent of the last line, possibly modified by `\x'. The `br' request finishes the current partial line, inserting a newline input token which is subsequently converted to a space when the diversion is reread. Note that the word space node has a fixed width which isn't stretchable anymore. To convert horizontal space nodes back to input tokens, use the `unformat' request. Macros only contain elements in the token list (and the node list is empty); diversions and strings can contain elements in both lists. Note that the `chop' request simply reduces the number of elements in a macro, string, or diversion by one. Exceptions are "compatibility save" and "compatibility ignore" input tokens which are ignored. The `substring' request also ignores those input tokens. Some requests like `tr' or `cflags' work on glyph identifiers only; this means that the associated glyph can be changed without destroying this association. This can be very helpful for substituting glyphs. In the following example, we assume that glyph `foo' isn't available by default, so we provide a substitution using the `fchar' request and map it to input character `x'. .fchar \[foo] foo .tr x \[foo] Now let us assume that we install an additional special font `bar' which has glyph `foo'. .special bar .rchar \[foo] Since glyphs defined with `fchar' are searched before glyphs in special fonts, we must call `rchar' to remove the definition of the fallback glyph. Anyway, the translation is still active; `x' now maps to the real glyph `foo'.  File: groff, Node: Gtroff Internals-Footnotes, Up: Gtroff Internals (1) Except the escapes `\f', `\F', `\H', `\m', `\M', `\R', `\s', and `\S' which are processed immediately if not in copy-in mode.  File: groff, Node: Debugging, Next: Implementation Differences, Prev: Gtroff Internals, Up: gtroff Reference Debugging ========= `gtroff' is not easy to debug, but there are some useful features and strategies for debugging. - Request: .lf line [filename] Change the line number and optionally the file name `gtroff' shall use for error and warning messages. LINE is the input line number of the _next_ line. Without argument, the request is ignored. This is a debugging aid for documents which are split into many files, then put together with `soelim' and other preprocessors. Usually, it isn't invoked manually. Note that other `troff' implementations (including the original AT&T version) handle `lf' differently. For them, LINE changes the line number of the _current_ line. - Request: .tm string - Request: .tm1 string - Request: .tmc string Send STRING to the standard error output; this is very useful for printing debugging messages among other things. STRING is read in copy mode. The `tm' request ignores leading spaces of STRING; `tm1' handles its argument similar to the `ds' request: a leading double quote in STRING is stripped to allow initial blanks. The `tmc' request is similar to `tm1' but does not append a newline (as is done in `tm' and `tm1'). - Request: .ab [string] Similar to the `tm' request, except that it causes `gtroff' to stop processing. With no argument it prints `User Abort.' to standard error. - Request: .ex The `ex' request also causes `gtroff' to stop processing; see also *Note I/O::. When doing something involved it is useful to leave the debugging statements in the code and have them turned on by a command line flag. .if \n(DB .tm debugging output To activate these statements say groff -rDB=1 file If it is known in advance that there will be many errors and no useful output, `gtroff' can be forced to suppress formatted output with the `-z' flag. - Request: .pm Print the entire symbol table on `stderr'. Names of all defined macros, strings, and diversions are print together with their size in bytes. Since `gtroff' sometimes adds nodes by itself, the returned size can be larger than expected. This request differs from UNIX `troff': `gtroff' reports the sizes of diversions, ignores an additional argument to print only the total of the sizes, and the size isn't returned in blocks of 128 characters. - Request: .pnr Print the names and contents of all currently defined number registers on `stderr'. - Request: .ptr Print the names and positions of all traps (not including input line traps and diversion traps) on `stderr'. Empty slots in the page trap list are printed as well, because they can affect the priority of subsequently planted traps. - Request: .fl Instruct `gtroff' to flush its output immediately. The intent is for interactive use, but this behaviour is currently not implemented in `gtroff'. Contrary to UNIX `troff', TTY output is sent to a device driver also (`grotty'), making it non-trivial to communicate interactively. This request causes a line break. - Request: .backtrace Print a backtrace of the input stack to the standard error stream. Consider the following in file `test': .de xxx . backtrace .. .de yyy . xxx .. . .yyy On execution, `gtroff' prints the following: test:2: backtrace: macro `xxx' test:5: backtrace: macro `yyy' test:8: backtrace: file `test' The option `-b' of `gtroff' internally calls a variant of this request on each error and warning. - Register: \n[slimit] Use the `slimit' number register to set the maximum number of objects on the input stack. If `slimit' is less than or equal to 0, there is no limit set. With no limit, a buggy recursive macro can exhaust virtual memory. The default value is 1000; this is a compile-time constant. - Request: .warnscale si Set the scaling indicator used in warnings to SI. Valid values for SI are `u', `i', `c', `p', and `P'. At startup, it is set to `i'. - Request: .spreadwarn [limit] Make `gtroff' emit a warning if the additional space inserted for each space between words in an output line is larger or equal to LIMIT. A negative value is changed to zero; no argument toggles the warning on and off without changing LIMIT. The default scaling indicator is `m'. At startup, `spreadwarn' is deactivated, and LIMIT is set to 3m. For example, .spreadwarn 0.2m will cause a warning if `gtroff' must add 0.2m or more for each interword space in a line. This request is active only if text is justified to both margins (using `.ad b'). `gtroff' has command line options for printing out more warnings (`-w') and for printing backtraces (`-b') when a warning or an error occurs. The most verbose level of warnings is `-ww'. - Request: .warn [flags] - Register: \n[.warn] Control the level of warnings checked for. The FLAGS are the sum of the numbers associated with each warning that is to be enabled; all other warnings are disabled. The number associated with each warning is listed below. For example, `.warn 0' disables all warnings, and `.warn 1' disables all warnings except that about missing glyphs. If no argument is given, all warnings are enabled. The read-only number register `.warn' contains the current warning level. * Menu: * Warnings::