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129 | .\" ======================================================================== | |
130 | .\" | |
131 | .IX Title "PERLFORM 1" | |
132 | .TH PERLFORM 1 "2006-01-07" "perl v5.8.8" "Perl Programmers Reference Guide" | |
133 | .SH "NAME" | |
134 | .IX Xref "format report chart" | |
135 | perlform \- Perl formats | |
136 | .SH "DESCRIPTION" | |
137 | .IX Header "DESCRIPTION" | |
138 | Perl has a mechanism to help you generate simple reports and charts. To | |
139 | facilitate this, Perl helps you code up your output page close to how it | |
140 | will look when it's printed. It can keep track of things like how many | |
141 | lines are on a page, what page you're on, when to print page headers, | |
142 | etc. Keywords are borrowed from \s-1FORTRAN:\s0 \fIformat()\fR to declare and \fIwrite()\fR | |
143 | to execute; see their entries in perlfunc. Fortunately, the layout is | |
144 | much more legible, more like \s-1BASIC\s0's \s-1PRINT\s0 \s-1USING\s0 statement. Think of it | |
145 | as a poor man's \fInroff\fR\|(1). | |
146 | .IX Xref "nroff" | |
147 | .PP | |
148 | Formats, like packages and subroutines, are declared rather than | |
149 | executed, so they may occur at any point in your program. (Usually it's | |
150 | best to keep them all together though.) They have their own namespace | |
151 | apart from all the other \*(L"types\*(R" in Perl. This means that if you have a | |
152 | function named \*(L"Foo\*(R", it is not the same thing as having a format named | |
153 | \&\*(L"Foo\*(R". However, the default name for the format associated with a given | |
154 | filehandle is the same as the name of the filehandle. Thus, the default | |
155 | format for \s-1STDOUT\s0 is named \*(L"\s-1STDOUT\s0\*(R", and the default format for filehandle | |
156 | \&\s-1TEMP\s0 is named \*(L"\s-1TEMP\s0\*(R". They just look the same. They aren't. | |
157 | .PP | |
158 | Output record formats are declared as follows: | |
159 | .PP | |
160 | .Vb 3 | |
161 | \& format NAME = | |
162 | \& FORMLIST | |
163 | \& . | |
164 | .Ve | |
165 | .PP | |
166 | If the name is omitted, format \*(L"\s-1STDOUT\s0\*(R" is defined. A single \*(L".\*(R" in | |
167 | column 1 is used to terminate a format. \s-1FORMLIST\s0 consists of a sequence | |
168 | of lines, each of which may be one of three types: | |
169 | .IP "1." 4 | |
170 | A comment, indicated by putting a '#' in the first column. | |
171 | .IP "2." 4 | |
172 | A \*(L"picture\*(R" line giving the format for one output line. | |
173 | .IP "3." 4 | |
174 | An argument line supplying values to plug into the previous picture line. | |
175 | .PP | |
176 | Picture lines contain output field definitions, intermingled with | |
177 | literal text. These lines do not undergo any kind of variable interpolation. | |
178 | Field definitions are made up from a set of characters, for starting and | |
179 | extending a field to its desired width. This is the complete set of | |
180 | characters for field definitions: | |
181 | .IX Xref "format, picture line @ ^ < | > # 0 . ... @* ^* ~ ~~" | |
182 | .PP | |
183 | .Vb 13 | |
184 | \& @ start of regular field | |
185 | \& ^ start of special field | |
186 | \& < pad character for left adjustification | |
187 | \& | pad character for centering | |
188 | \& > pad character for right adjustificat | |
189 | \& # pad character for a right justified numeric field | |
190 | \& 0 instead of first #: pad number with leading zeroes | |
191 | \& . decimal point within a numeric field | |
192 | \& ... terminate a text field, show "..." as truncation evidence | |
193 | \& @* variable width field for a multi-line value | |
194 | \& ^* variable width field for next line of a multi-line value | |
195 | \& ~ suppress line with all fields empty | |
196 | \& ~~ repeat line until all fields are exhausted | |
197 | .Ve | |
198 | .PP | |
199 | Each field in a picture line starts with either \*(L"@\*(R" (at) or \*(L"^\*(R" (caret), | |
200 | indicating what we'll call, respectively, a \*(L"regular\*(R" or \*(L"special\*(R" field. | |
201 | The choice of pad characters determines whether a field is textual or | |
202 | numeric. The tilde operators are not part of a field. Let's look at | |
203 | the various possibilities in detail. | |
204 | .Sh "Text Fields" | |
205 | .IX Xref "format, text field" | |
206 | .IX Subsection "Text Fields" | |
207 | The length of the field is supplied by padding out the field with multiple | |
208 | "<\*(L", \*(R">\*(L", or \*(R"|\*(L" characters to specify a non-numeric field with, | |
209 | respectively, left justification, right justification, or centering. | |
210 | For a regular field, the value (up to the first newline) is taken and | |
211 | printed according to the selected justification, truncating excess characters. | |
212 | If you terminate a text field with \*(R"...", three dots will be shown if | |
213 | the value is truncated. A special text field may be used to do rudimentary | |
214 | multi-line text block filling; see \*(L"Using Fill Mode\*(R" for details. | |
215 | .PP | |
216 | .Vb 7 | |
217 | \& Example: | |
218 | \& format STDOUT = | |
219 | \& @<<<<<< @|||||| @>>>>>> | |
220 | \& "left", "middle", "right" | |
221 | \& . | |
222 | \& Output: | |
223 | \& left middle right | |
224 | .Ve | |
225 | .Sh "Numeric Fields" | |
226 | .IX Xref "# format, numeric field" | |
227 | .IX Subsection "Numeric Fields" | |
228 | Using \*(L"#\*(R" as a padding character specifies a numeric field, with | |
229 | right justification. An optional \*(L".\*(R" defines the position of the | |
230 | decimal point. With a \*(L"0\*(R" (zero) instead of the first \*(L"#\*(R", the | |
231 | formatted number will be padded with leading zeroes if necessary. | |
232 | A special numeric field is blanked out if the value is undefined. | |
233 | If the resulting value would exceed the width specified the field is | |
234 | filled with \*(L"#\*(R" as overflow evidence. | |
235 | .PP | |
236 | .Vb 7 | |
237 | \& Example: | |
238 | \& format STDOUT = | |
239 | \& @### @.### @##.### @### @### ^#### | |
240 | \& 42, 3.1415, undef, 0, 10000, undef | |
241 | \& . | |
242 | \& Output: | |
243 | \& 42 3.142 0.000 0 #### | |
244 | .Ve | |
245 | .Sh "The Field @* for Variable Width Multi-Line Text" | |
246 | .IX Xref "@*" | |
247 | .IX Subsection "The Field @* for Variable Width Multi-Line Text" | |
248 | The field \*(L"@*\*(R" can be used for printing multi\-line, nontruncated | |
249 | values; it should (but need not) appear by itself on a line. A final | |
250 | line feed is chomped off, but all other characters are emitted verbatim. | |
251 | .Sh "The Field ^* for Variable Width One-line-at-a-time Text" | |
252 | .IX Xref "^*" | |
253 | .IX Subsection "The Field ^* for Variable Width One-line-at-a-time Text" | |
254 | Like \*(L"@*\*(R", this is a variable width field. The value supplied must be a | |
255 | scalar variable. Perl puts the first line (up to the first \*(L"\en\*(R") of the | |
256 | text into the field, and then chops off the front of the string so that | |
257 | the next time the variable is referenced, more of the text can be printed. | |
258 | The variable will \fInot\fR be restored. | |
259 | .PP | |
260 | .Vb 12 | |
261 | \& Example: | |
262 | \& $text = "line 1\enline 2\enline 3"; | |
263 | \& format STDOUT = | |
264 | \& Text: ^* | |
265 | \& $text | |
266 | \& ~~ ^* | |
267 | \& $text | |
268 | \& . | |
269 | \& Output: | |
270 | \& Text: line 1 | |
271 | \& line 2 | |
272 | \& line 3 | |
273 | .Ve | |
274 | .Sh "Specifying Values" | |
275 | .IX Xref "format, specifying values" | |
276 | .IX Subsection "Specifying Values" | |
277 | The values are specified on the following format line in the same order as | |
278 | the picture fields. The expressions providing the values must be | |
279 | separated by commas. They are all evaluated in a list context | |
280 | before the line is processed, so a single list expression could produce | |
281 | multiple list elements. The expressions may be spread out to more than | |
282 | one line if enclosed in braces. If so, the opening brace must be the first | |
283 | token on the first line. If an expression evaluates to a number with a | |
284 | decimal part, and if the corresponding picture specifies that the decimal | |
285 | part should appear in the output (that is, any picture except multiple \*(L"#\*(R" | |
286 | characters \fBwithout\fR an embedded \*(L".\*(R"), the character used for the decimal | |
287 | point is \fBalways\fR determined by the current \s-1LC_NUMERIC\s0 locale. This | |
288 | means that, if, for example, the run-time environment happens to specify a | |
289 | German locale, \*(L",\*(R" will be used instead of the default \*(L".\*(R". See | |
290 | perllocale and \*(L"\s-1WARNINGS\s0\*(R" for more information. | |
291 | .Sh "Using Fill Mode" | |
292 | .IX Xref "format, fill mode" | |
293 | .IX Subsection "Using Fill Mode" | |
294 | On text fields the caret enables a kind of fill mode. Instead of an | |
295 | arbitrary expression, the value supplied must be a scalar variable | |
296 | that contains a text string. Perl puts the next portion of the text into | |
297 | the field, and then chops off the front of the string so that the next time | |
298 | the variable is referenced, more of the text can be printed. (Yes, this | |
299 | means that the variable itself is altered during execution of the \fIwrite()\fR | |
300 | call, and is not restored.) The next portion of text is determined by | |
301 | a crude line breaking algorithm. You may use the carriage return character | |
302 | (\f(CW\*(C`\er\*(C'\fR) to force a line break. You can change which characters are legal | |
303 | to break on by changing the variable \f(CW$:\fR (that's | |
304 | \&\f(CW$FORMAT_LINE_BREAK_CHARACTERS\fR if you're using the English module) to a | |
305 | list of the desired characters. | |
306 | .PP | |
307 | Normally you would use a sequence of fields in a vertical stack associated | |
308 | with the same scalar variable to print out a block of text. You might wish | |
309 | to end the final field with the text \*(L"...\*(R", which will appear in the output | |
310 | if the text was too long to appear in its entirety. | |
311 | .Sh "Suppressing Lines Where All Fields Are Void" | |
312 | .IX Xref "format, suppressing lines" | |
313 | .IX Subsection "Suppressing Lines Where All Fields Are Void" | |
314 | Using caret fields can produce lines where all fields are blank. You can | |
315 | suppress such lines by putting a \*(L"~\*(R" (tilde) character anywhere in the | |
316 | line. The tilde will be translated to a space upon output. | |
317 | .Sh "Repeating Format Lines" | |
318 | .IX Xref "format, repeating lines" | |
319 | .IX Subsection "Repeating Format Lines" | |
320 | If you put two contiguous tilde characters \*(L"~~\*(R" anywhere into a line, | |
321 | the line will be repeated until all the fields on the line are exhausted, | |
322 | i.e. undefined. For special (caret) text fields this will occur sooner or | |
323 | later, but if you use a text field of the at variety, the expression you | |
324 | supply had better not give the same value every time forever! (\f(CW\*(C`shift(@f)\*(C'\fR | |
325 | is a simple example that would work.) Don't use a regular (at) numeric | |
326 | field in such lines, because it will never go blank. | |
327 | .Sh "Top of Form Processing" | |
328 | .IX Xref "format, top of form top header" | |
329 | .IX Subsection "Top of Form Processing" | |
330 | Top-of-form processing is by default handled by a format with the | |
331 | same name as the current filehandle with \*(L"_TOP\*(R" concatenated to it. | |
332 | It's triggered at the top of each page. See \*(L"write\*(R" in perlfunc. | |
333 | .PP | |
334 | Examples: | |
335 | .PP | |
336 | .Vb 10 | |
337 | \& # a report on the /etc/passwd file | |
338 | \& format STDOUT_TOP = | |
339 | \& Passwd File | |
340 | \& Name Login Office Uid Gid Home | |
341 | \& ------------------------------------------------------------------ | |
342 | \& . | |
343 | \& format STDOUT = | |
344 | \& @<<<<<<<<<<<<<<<<<< @||||||| @<<<<<<@>>>> @>>>> @<<<<<<<<<<<<<<<<< | |
345 | \& $name, $login, $office,$uid,$gid, $home | |
346 | \& . | |
347 | .Ve | |
348 | .PP | |
349 | .Vb 29 | |
350 | \& # a report from a bug report form | |
351 | \& format STDOUT_TOP = | |
352 | \& Bug Reports | |
353 | \& @<<<<<<<<<<<<<<<<<<<<<<< @||| @>>>>>>>>>>>>>>>>>>>>>>> | |
354 | \& $system, $%, $date | |
355 | \& ------------------------------------------------------------------ | |
356 | \& . | |
357 | \& format STDOUT = | |
358 | \& Subject: @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
359 | \& $subject | |
360 | \& Index: @<<<<<<<<<<<<<<<<<<<<<<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
361 | \& $index, $description | |
362 | \& Priority: @<<<<<<<<<< Date: @<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
363 | \& $priority, $date, $description | |
364 | \& From: @<<<<<<<<<<<<<<<<<<<<<<<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
365 | \& $from, $description | |
366 | \& Assigned to: @<<<<<<<<<<<<<<<<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
367 | \& $programmer, $description | |
368 | \& ~ ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
369 | \& $description | |
370 | \& ~ ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
371 | \& $description | |
372 | \& ~ ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
373 | \& $description | |
374 | \& ~ ^<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
375 | \& $description | |
376 | \& ~ ^<<<<<<<<<<<<<<<<<<<<<<<... | |
377 | \& $description | |
378 | \& . | |
379 | .Ve | |
380 | .PP | |
381 | It is possible to intermix \fIprint()\fRs with \fIwrite()\fRs on the same output | |
382 | channel, but you'll have to handle \f(CW\*(C`$\-\*(C'\fR (\f(CW$FORMAT_LINES_LEFT\fR) | |
383 | yourself. | |
384 | .Sh "Format Variables" | |
385 | .IX Xref "format variables format, variables" | |
386 | .IX Subsection "Format Variables" | |
387 | The current format name is stored in the variable \f(CW$~\fR (\f(CW$FORMAT_NAME\fR), | |
388 | and the current top of form format name is in \f(CW$^\fR (\f(CW$FORMAT_TOP_NAME\fR). | |
389 | The current output page number is stored in \f(CW$%\fR (\f(CW$FORMAT_PAGE_NUMBER\fR), | |
390 | and the number of lines on the page is in \f(CW$=\fR (\f(CW$FORMAT_LINES_PER_PAGE\fR). | |
391 | Whether to autoflush output on this handle is stored in \f(CW$|\fR | |
392 | (\f(CW$OUTPUT_AUTOFLUSH\fR). The string output before each top of page (except | |
393 | the first) is stored in \f(CW$^L\fR (\f(CW$FORMAT_FORMFEED\fR). These variables are | |
394 | set on a per-filehandle basis, so you'll need to \fIselect()\fR into a different | |
395 | one to affect them: | |
396 | .PP | |
397 | .Vb 4 | |
398 | \& select((select(OUTF), | |
399 | \& $~ = "My_Other_Format", | |
400 | \& $^ = "My_Top_Format" | |
401 | \& )[0]); | |
402 | .Ve | |
403 | .PP | |
404 | Pretty ugly, eh? It's a common idiom though, so don't be too surprised | |
405 | when you see it. You can at least use a temporary variable to hold | |
406 | the previous filehandle: (this is a much better approach in general, | |
407 | because not only does legibility improve, you now have intermediary | |
408 | stage in the expression to single-step the debugger through): | |
409 | .PP | |
410 | .Vb 4 | |
411 | \& $ofh = select(OUTF); | |
412 | \& $~ = "My_Other_Format"; | |
413 | \& $^ = "My_Top_Format"; | |
414 | \& select($ofh); | |
415 | .Ve | |
416 | .PP | |
417 | If you use the English module, you can even read the variable names: | |
418 | .PP | |
419 | .Vb 5 | |
420 | \& use English '-no_match_vars'; | |
421 | \& $ofh = select(OUTF); | |
422 | \& $FORMAT_NAME = "My_Other_Format"; | |
423 | \& $FORMAT_TOP_NAME = "My_Top_Format"; | |
424 | \& select($ofh); | |
425 | .Ve | |
426 | .PP | |
427 | But you still have those funny \fIselect()\fRs. So just use the FileHandle | |
428 | module. Now, you can access these special variables using lowercase | |
429 | method names instead: | |
430 | .PP | |
431 | .Vb 3 | |
432 | \& use FileHandle; | |
433 | \& format_name OUTF "My_Other_Format"; | |
434 | \& format_top_name OUTF "My_Top_Format"; | |
435 | .Ve | |
436 | .PP | |
437 | Much better! | |
438 | .SH "NOTES" | |
439 | .IX Header "NOTES" | |
440 | Because the values line may contain arbitrary expressions (for at fields, | |
441 | not caret fields), you can farm out more sophisticated processing | |
442 | to other functions, like \fIsprintf()\fR or one of your own. For example: | |
443 | .PP | |
444 | .Vb 4 | |
445 | \& format Ident = | |
446 | \& @<<<<<<<<<<<<<<< | |
447 | \& &commify($n) | |
448 | \& . | |
449 | .Ve | |
450 | .PP | |
451 | To get a real at or caret into the field, do this: | |
452 | .PP | |
453 | .Vb 4 | |
454 | \& format Ident = | |
455 | \& I have an @ here. | |
456 | \& "@" | |
457 | \& . | |
458 | .Ve | |
459 | .PP | |
460 | To center a whole line of text, do something like this: | |
461 | .PP | |
462 | .Vb 4 | |
463 | \& format Ident = | |
464 | \& @||||||||||||||||||||||||||||||||||||||||||||||| | |
465 | \& "Some text line" | |
466 | \& . | |
467 | .Ve | |
468 | .PP | |
469 | There is no builtin way to say \*(L"float this to the right hand side | |
470 | of the page, however wide it is.\*(R" You have to specify where it goes. | |
471 | The truly desperate can generate their own format on the fly, based | |
472 | on the current number of columns, and then \fIeval()\fR it: | |
473 | .PP | |
474 | .Vb 9 | |
475 | \& $format = "format STDOUT = \en" | |
476 | \& . '^' . '<' x $cols . "\en" | |
477 | \& . '$entry' . "\en" | |
478 | \& . "\et^" . "<" x ($cols-8) . "~~\en" | |
479 | \& . '$entry' . "\en" | |
480 | \& . ".\en"; | |
481 | \& print $format if $Debugging; | |
482 | \& eval $format; | |
483 | \& die $@ if $@; | |
484 | .Ve | |
485 | .PP | |
486 | Which would generate a format looking something like this: | |
487 | .PP | |
488 | .Vb 6 | |
489 | \& format STDOUT = | |
490 | \& ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< | |
491 | \& $entry | |
492 | \& ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<~~ | |
493 | \& $entry | |
494 | \& . | |
495 | .Ve | |
496 | .PP | |
497 | Here's a little program that's somewhat like \fIfmt\fR\|(1): | |
498 | .PP | |
499 | .Vb 3 | |
500 | \& format = | |
501 | \& ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< ~~ | |
502 | \& $_ | |
503 | .Ve | |
504 | .PP | |
505 | .Vb 1 | |
506 | \& . | |
507 | .Ve | |
508 | .PP | |
509 | .Vb 5 | |
510 | \& $/ = ''; | |
511 | \& while (<>) { | |
512 | \& s/\es*\en\es*/ /g; | |
513 | \& write; | |
514 | \& } | |
515 | .Ve | |
516 | .Sh "Footers" | |
517 | .IX Xref "format, footer footer" | |
518 | .IX Subsection "Footers" | |
519 | While \f(CW$FORMAT_TOP_NAME\fR contains the name of the current header format, | |
520 | there is no corresponding mechanism to automatically do the same thing | |
521 | for a footer. Not knowing how big a format is going to be until you | |
522 | evaluate it is one of the major problems. It's on the \s-1TODO\s0 list. | |
523 | .PP | |
524 | Here's one strategy: If you have a fixed-size footer, you can get footers | |
525 | by checking \f(CW$FORMAT_LINES_LEFT\fR before each \fIwrite()\fR and print the footer | |
526 | yourself if necessary. | |
527 | .PP | |
528 | Here's another strategy: Open a pipe to yourself, using \f(CW\*(C`open(MYSELF, "|\-")\*(C'\fR | |
529 | (see \*(L"\fIopen()\fR\*(R" in perlfunc) and always \fIwrite()\fR to \s-1MYSELF\s0 instead of \s-1STDOUT\s0. | |
530 | Have your child process massage its \s-1STDIN\s0 to rearrange headers and footers | |
531 | however you like. Not very convenient, but doable. | |
532 | .Sh "Accessing Formatting Internals" | |
533 | .IX Xref "format, internals" | |
534 | .IX Subsection "Accessing Formatting Internals" | |
535 | For low-level access to the formatting mechanism. you may use \fIformline()\fR | |
536 | and access \f(CW$^A\fR (the \f(CW$ACCUMULATOR\fR variable) directly. | |
537 | .PP | |
538 | For example: | |
539 | .PP | |
540 | .Vb 3 | |
541 | \& $str = formline <<'END', 1,2,3; | |
542 | \& @<<< @||| @>>> | |
543 | \& END | |
544 | .Ve | |
545 | .PP | |
546 | .Vb 1 | |
547 | \& print "Wow, I just stored `$^A' in the accumulator!\en"; | |
548 | .Ve | |
549 | .PP | |
550 | Or to make an \fIswrite()\fR subroutine, which is to \fIwrite()\fR what \fIsprintf()\fR | |
551 | is to \fIprintf()\fR, do this: | |
552 | .PP | |
553 | .Vb 8 | |
554 | \& use Carp; | |
555 | \& sub swrite { | |
556 | \& croak "usage: swrite PICTURE ARGS" unless @_; | |
557 | \& my $format = shift; | |
558 | \& $^A = ""; | |
559 | \& formline($format,@_); | |
560 | \& return $^A; | |
561 | \& } | |
562 | .Ve | |
563 | .PP | |
564 | .Vb 5 | |
565 | \& $string = swrite(<<'END', 1, 2, 3); | |
566 | \& Check me out | |
567 | \& @<<< @||| @>>> | |
568 | \& END | |
569 | \& print $string; | |
570 | .Ve | |
571 | .SH "WARNINGS" | |
572 | .IX Header "WARNINGS" | |
573 | The lone dot that ends a format can also prematurely end a mail | |
574 | message passing through a misconfigured Internet mailer (and based on | |
575 | experience, such misconfiguration is the rule, not the exception). So | |
576 | when sending format code through mail, you should indent it so that | |
577 | the format-ending dot is not on the left margin; this will prevent | |
578 | \&\s-1SMTP\s0 cutoff. | |
579 | .PP | |
580 | Lexical variables (declared with \*(L"my\*(R") are not visible within a | |
581 | format unless the format is declared within the scope of the lexical | |
582 | variable. (They weren't visible at all before version 5.001.) | |
583 | .PP | |
584 | Formats are the only part of Perl that unconditionally use information | |
585 | from a program's locale; if a program's environment specifies an | |
586 | \&\s-1LC_NUMERIC\s0 locale, it is always used to specify the decimal point | |
587 | character in formatted output. Perl ignores all other aspects of locale | |
588 | handling unless the \f(CW\*(C`use locale\*(C'\fR pragma is in effect. Formatted output | |
589 | cannot be controlled by \f(CW\*(C`use locale\*(C'\fR because the pragma is tied to the | |
590 | block structure of the program, and, for historical reasons, formats | |
591 | exist outside that block structure. See perllocale for further | |
592 | discussion of locale handling. | |
593 | .PP | |
594 | Within strings that are to be displayed in a fixed length text field, | |
595 | each control character is substituted by a space. (But remember the | |
596 | special meaning of \f(CW\*(C`\er\*(C'\fR when using fill mode.) This is done to avoid | |
597 | misalignment when control characters \*(L"disappear\*(R" on some output media. |