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5.33 I/O

gtroff has several requests for including files:

Request: .so file
Request: .soquiet file

Replace the so request’s control line with the contents of the file named by the argument, “sourcing” it. file is sought in the directories specified by -I command-line option. If file does not exist, a warning in category ‘file’ is produced and the request has no further effect. See Warnings, for information about the enablement and suppression of warnings.

so can be useful for large documents; e.g., allowing each chapter of a book to be kept in a separate file. However, files interpolated with so are not preprocessed; to overcome this limitation, see the gsoelim(1) man page.

Since GNU troff replaces the entire control line with the contents of a file, it matters whether file is terminated with a newline or not. Assume that file xxx contains only the word ‘foo’ without a trailing newline.

$ printf 'foo' > xxx

The situation is
.so xxx
    ⇒ The situation is foobar.

soquiet works the same way, except that no warning diagnostic is issued if file does not exist.

Request: .pso command

Read the standard output from the specified command and include it in place of the pso request.

It is an error to use this request in safer mode, which is the default. Invoke GNU troff or a front end with the -U option to enable unsafe mode.

The comment regarding a final newline for the so request is valid for pso also.

Request: .mso file
Request: .msoquiet file

Identical to the so and soquiet requests, respectively, except that gtroff searches for the specified file in the same directories as macro files for the -m command-line option. If the file name to be included has the form name.tmac and it isn’t found, these requests try to include 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, trf adds one. Both requests cause a break.

When used in a diversion, these requests embed a node (see Gtroff Internals) in it that, when reread, causes the contents of file to be transparently copied to the output. In AT&T troff, the contents of file are immediately copied 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 (see Identifiers).

For cf, within a diversion, “completely unprocessed” means that each line of a file to be inserted is handled as if it were preceded by \!\\!.

To define a macro x containing the contents of file f, use

.ev 1
.di x
.trf f

The calls to ev prevent the partially collected output line from becoming part of the diversion (see Diversions).

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:

.sp 2
Body of letter.
.nx repeat.let

When this is run, a file containing the following lines should be redirected in. 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 GNU troff to stop processing. If this were not there, troff 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,

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.

It is an error to use this request in safer mode, which is the default. Invoke GNU troff or a front end with the -U option to enable 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.

The intermediate output format of GNU troff 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 anywhere, so it is up to the user to do so.

It is an error to use this request in safer mode; this is the default. Give GNU troff or a front end program the -U option to enable unsafe mode.

The following code fragment introduces the current time into a document.

.sy perl -e 'printf ".nr H %d\\ M %d\\ S %d\\n",\
             (localtime(time))[2,1,0]' > /tmp/x\n[$$]
.so /tmp/x\n[$$]
.sy rm /tmp/x\n[$$]

This works by having the Perl script (run by sy) write nr requests that set the registers H, M, and S to a temporary file. The roff document then reads the temporary file using the so request.

The registers seconds, minutes, and hours, initialized at startup of GNU troff, should satisfy most requirements. Use the af request to format their values for output.

.af hours 00
.af minutes 00
.af seconds 00
    ⇒ 02:17:54

The writable register systat 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.

It is an error to use these requests in safer mode; this is the default. Give GNU troff or a front end program the -U option to enable 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: an initial neutral double quote in contents is stripped to allow embedding of leading spaces, and it is read in copy 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 sequence: \Ve
Escape sequence: \V(ev
Escape sequence: \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(3). \V is interpreted even in copy mode (see Copy Mode).

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