| 1 | .\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.32 |
| 2 | .\" |
| 3 | .\" Standard preamble: |
| 4 | .\" ======================================================================== |
| 5 | .de Sh \" Subsection heading |
| 6 | .br |
| 7 | .if t .Sp |
| 8 | .ne 5 |
| 9 | .PP |
| 10 | \fB\\$1\fR |
| 11 | .PP |
| 12 | .. |
| 13 | .de Sp \" Vertical space (when we can't use .PP) |
| 14 | .if t .sp .5v |
| 15 | .if n .sp |
| 16 | .. |
| 17 | .de Vb \" Begin verbatim text |
| 18 | .ft CW |
| 19 | .nf |
| 20 | .ne \\$1 |
| 21 | .. |
| 22 | .de Ve \" End verbatim text |
| 23 | .ft R |
| 24 | .fi |
| 25 | .. |
| 26 | .\" Set up some character translations and predefined strings. \*(-- will |
| 27 | .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left |
| 28 | .\" double quote, and \*(R" will give a right double quote. | will give a |
| 29 | .\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to |
| 30 | .\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C' |
| 31 | .\" expand to `' in nroff, nothing in troff, for use with C<>. |
| 32 | .tr \(*W-|\(bv\*(Tr |
| 33 | .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' |
| 34 | .ie n \{\ |
| 35 | . ds -- \(*W- |
| 36 | . ds PI pi |
| 37 | . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch |
| 38 | . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch |
| 39 | . ds L" "" |
| 40 | . ds R" "" |
| 41 | . ds C` "" |
| 42 | . ds C' "" |
| 43 | 'br\} |
| 44 | .el\{\ |
| 45 | . ds -- \|\(em\| |
| 46 | . ds PI \(*p |
| 47 | . ds L" `` |
| 48 | . ds R" '' |
| 49 | 'br\} |
| 50 | .\" |
| 51 | .\" If the F register is turned on, we'll generate index entries on stderr for |
| 52 | .\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index |
| 53 | .\" entries marked with X<> in POD. Of course, you'll have to process the |
| 54 | .\" output yourself in some meaningful fashion. |
| 55 | .if \nF \{\ |
| 56 | . de IX |
| 57 | . tm Index:\\$1\t\\n%\t"\\$2" |
| 58 | .. |
| 59 | . nr % 0 |
| 60 | . rr F |
| 61 | .\} |
| 62 | .\" |
| 63 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
| 64 | .\" way too many mistakes in technical documents. |
| 65 | .hy 0 |
| 66 | .if n .na |
| 67 | .\" |
| 68 | .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). |
| 69 | .\" Fear. Run. Save yourself. No user-serviceable parts. |
| 70 | . \" fudge factors for nroff and troff |
| 71 | .if n \{\ |
| 72 | . ds #H 0 |
| 73 | . ds #V .8m |
| 74 | . ds #F .3m |
| 75 | . ds #[ \f1 |
| 76 | . ds #] \fP |
| 77 | .\} |
| 78 | .if t \{\ |
| 79 | . ds #H ((1u-(\\\\n(.fu%2u))*.13m) |
| 80 | . ds #V .6m |
| 81 | . ds #F 0 |
| 82 | . ds #[ \& |
| 83 | . ds #] \& |
| 84 | .\} |
| 85 | . \" simple accents for nroff and troff |
| 86 | .if n \{\ |
| 87 | . ds ' \& |
| 88 | . ds ` \& |
| 89 | . ds ^ \& |
| 90 | . ds , \& |
| 91 | . ds ~ ~ |
| 92 | . ds / |
| 93 | .\} |
| 94 | .if t \{\ |
| 95 | . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" |
| 96 | . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' |
| 97 | . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' |
| 98 | . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' |
| 99 | . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' |
| 100 | . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' |
| 101 | .\} |
| 102 | . \" troff and (daisy-wheel) nroff accents |
| 103 | .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' |
| 104 | .ds 8 \h'\*(#H'\(*b\h'-\*(#H' |
| 105 | .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] |
| 106 | .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' |
| 107 | .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' |
| 108 | .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] |
| 109 | .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] |
| 110 | .ds ae a\h'-(\w'a'u*4/10)'e |
| 111 | .ds Ae A\h'-(\w'A'u*4/10)'E |
| 112 | . \" corrections for vroff |
| 113 | .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' |
| 114 | .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' |
| 115 | . \" for low resolution devices (crt and lpr) |
| 116 | .if \n(.H>23 .if \n(.V>19 \ |
| 117 | \{\ |
| 118 | . ds : e |
| 119 | . ds 8 ss |
| 120 | . ds o a |
| 121 | . ds d- d\h'-1'\(ga |
| 122 | . ds D- D\h'-1'\(hy |
| 123 | . ds th \o'bp' |
| 124 | . ds Th \o'LP' |
| 125 | . ds ae ae |
| 126 | . ds Ae AE |
| 127 | .\} |
| 128 | .rm #[ #] #H #V #F C |
| 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. |