raw/mann/format.n

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   8 '\" RCS: @(#) $Id: format.n,v 1.1 2003/12/20 03:31:54 bbbush Exp $
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  10 '\" The definitions below are for supplemental macros used in Tcl/Tk
  11 '\" manual entries.
  12 '\"
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  61 '\"
  62 '\" .OP cmdName dbName dbClass
  63 '\"     Start of description of a specific option.  cmdName gives the
  64 '\"     option's name as specified in the class command, dbName gives
  65 '\"     the option's name in the option database, and dbClass gives
  66 '\"     the option's class in the option database.
  67 '\"
  68 '\" .UL arg1 arg2
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  70 '\"
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 177 .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
 178 .\}
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 206 '\"     # SO - start of list of standard options
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 208 .SH "STANDARD OPTIONS"
 209 .LP
 210 .nf
 211 .ta 5.5c 11c
 212 .ft B
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 215 .de SE
 216 .fi
 217 .ft R
 218 .LP
 219 See the \\fBoptions\\fR manual entry for details on the standard options.
 220 ..
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 222 .de OP
 223 .LP
 224 .nf
 225 .ta 4c
 226 Command-Line Name:      \\fB\\$1\\fR
 227 Database Name:  \\fB\\$2\\fR
 228 Database Class: \\fB\\$3\\fR
 229 .fi
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 243 .de UL
 244 \\$1\l'|0\(ul'\\$2
 245 ..
 246 .TH format n 8.1 Tcl "Tcl Built-In Commands"
 247 .BS
 248 '\" Note:  do not modify the .SH NAME line immediately below!
 249 .SH NAME
 250 format \- Format a string in the style of sprintf
 251 .SH SYNOPSIS
 252 \fBformat \fIformatString \fR?\fIarg arg ...\fR?
 253 .BE
 254
 255 .SH INTRODUCTION
 256 .PP
 257 This command generates a formatted string in the same way as the
 258 ANSI C \fBsprintf\fR procedure (it uses \fBsprintf\fR in its
 259 implementation).
 260 \fIFormatString\fR indicates how to format the result, using
 261 \fB%\fR conversion specifiers as in \fBsprintf\fR, and the additional
 262 arguments, if any, provide values to be substituted into the result.
 263 The return value from \fBformat\fR is the formatted string.
 264
 265 .SH "DETAILS ON FORMATTING"
 266 .PP
 267 The command operates by scanning \fIformatString\fR from left to right.
 268 Each character from the format string is appended to the result
 269 string unless it is a percent sign.
 270 If the character is a \fB%\fR then it is not copied to the result string.
 271 Instead, the characters following the \fB%\fR character are treated as
 272 a conversion specifier.
 273 The conversion specifier controls the conversion of the next successive
 274 \fIarg\fR to a particular format and the result is appended to
 275 the result string in place of the conversion specifier.
 276 If there are multiple conversion specifiers in the format string,
 277 then each one controls the conversion of one additional \fIarg\fR.
 278 The \fBformat\fR command must be given enough \fIarg\fRs to meet the needs
 279 of all of the conversion specifiers in \fIformatString\fR.
 280 .PP
 281 Each conversion specifier may contain up to six different parts:
 282 an XPG3 position specifier,
 283 a set of flags, a minimum field width, a precision, a length modifier,
 284 and a conversion character.
 285 Any of these fields may be omitted except for the conversion character.
 286 The fields that are present must appear in the order given above.
 287 The paragraphs below discuss each of these fields in turn.
 288 .PP
 289 If the \fB%\fR is followed by a decimal number and a \fB$\fR, as in
 290 ``\fB%2$d\fR'', then the value to convert is not taken from the
 291 next sequential argument.
 292 Instead, it is taken from the argument indicated by the number,
 293 where 1 corresponds to the first \fIarg\fR.
 294 If the conversion specifier requires multiple arguments because
 295 of \fB*\fR characters in the specifier then
 296 successive arguments are used, starting with the argument
 297 given by the number.
 298 This follows the XPG3 conventions for positional specifiers.
 299 If there are any positional specifiers in \fIformatString\fR
 300 then all of the specifiers must be positional.
 301 .PP
 302 The second portion of a conversion specifier may contain any of the
 303 following flag characters, in any order:
 304 .TP 10
 305 \fB\-\fR
 306 Specifies that the converted argument should be left-justified
 307 in its field (numbers are normally right-justified with leading
 308 spaces if needed).
 309 .TP 10
 310 \fB+\fR
 311 Specifies that a number should always be printed with a sign,
 312 even if positive.
 313 .TP 10
 314 \fIspace\fR
 315 Specifies that a space should be added to the beginning of the
 316 number if the first character isn't a sign.
 317 .TP 10
 318 \fB0\fR
 319 Specifies that the number should be padded on the left with
 320 zeroes instead of spaces.
 321 .TP 10
 322 \fB#\fR
 323 Requests an alternate output form. For \fBo\fR and \fBO\fR
 324 conversions it guarantees that the first digit is always \fB0\fR.
 325 For \fBx\fR or \fBX\fR conversions, \fB0x\fR or \fB0X\fR (respectively)
 326 will be added to the beginning of the result unless it is zero.
 327 For all floating-point conversions (\fBe\fR, \fBE\fR, \fBf\fR,
 328 \fBg\fR, and \fBG\fR) it guarantees that the result always
 329 has a decimal point.
 330 For \fBg\fR and \fBG\fR conversions it specifies that
 331 trailing zeroes should not be removed.
 332 .PP
 333 The third portion of a conversion specifier is a number giving a
 334 minimum field width for this conversion.
 335 It is typically used to make columns line up in tabular printouts.
 336 If the converted argument contains fewer characters than the
 337 minimum field width then it will be padded so that it is as wide
 338 as the minimum field width.
 339 Padding normally occurs by adding extra spaces on the left of the
 340 converted argument, but the \fB0\fR and \fB\-\fR flags
 341 may be used to specify padding with zeroes on the left or with
 342 spaces on the right, respectively.
 343 If the minimum field width is specified as \fB*\fR rather than
 344 a number, then the next argument to the \fBformat\fR command
 345 determines the minimum field width; it must be a numeric string.
 346 .PP
 347 The fourth portion of a conversion specifier is a precision,
 348 which consists of a period followed by a number.
 349 The number is used in different ways for different conversions.
 350 For \fBe\fR, \fBE\fR, and \fBf\fR conversions it specifies the number
 351 of digits to appear to the right of the decimal point.
 352 For \fBg\fR and \fBG\fR conversions it specifies the total number
 353 of digits to appear, including those on both sides of the decimal
 354 point (however, trailing zeroes after the decimal point will still
 355 be omitted unless the \fB#\fR flag has been specified).
 356 For integer conversions, it specifies a minimum number of digits
 357 to print (leading zeroes will be added if necessary).
 358 For \fBs\fR conversions it specifies the maximum number of characters to be
 359 printed; if the string is longer than this then the trailing characters will be dropped.
 360 If the precision is specified with \fB*\fR rather than a number
 361 then the next argument to the \fBformat\fR command determines the precision;
 362 it must be a numeric string.
 363 .PP
 364 The fifth part of a conversion specifier is a length modifier,
 365 which must be \fBh\fR or \fBl\fR.
 366 If it is \fBh\fR it specifies that the numeric value should be
 367 truncated to a 16-bit value before converting.
 368 This option is rarely useful.
 369 The \fBl\fR modifier is ignored.
 370 .PP
 371 The last thing in a conversion specifier is an alphabetic character
 372 that determines what kind of conversion to perform.
 373 The following conversion characters are currently supported:
 374 .TP 10
 375 \fBd\fR
 376 Convert integer to signed decimal string.
 377 .TP 10
 378 \fBu\fR
 379 Convert integer to unsigned decimal string.
 380 .TP 10
 381 \fBi\fR
 382 Convert integer to signed decimal string;  the integer may either be
 383 in decimal, in octal (with a leading \fB0\fR) or in hexadecimal
 384 (with a leading \fB0x\fR).
 385 .TP 10
 386 \fBo\fR
 387 Convert integer to unsigned octal string.
 388 .TP 10
 389 \fBx\fR or \fBX\fR
 390 Convert integer to unsigned hexadecimal string, using digits
 391 ``0123456789abcdef'' for \fBx\fR and ``0123456789ABCDEF'' for \fBX\fR).
 392 .VS
 393 .TP 10
 394 \fBc\fR
 395 Convert integer to the Unicode character it represents.
 396 .VE
 397 .TP 10
 398 \fBs\fR
 399 No conversion; just insert string.
 400 .TP 10
 401 \fBf\fR
 402 Convert floating-point number to signed decimal string of
 403 the form \fIxx.yyy\fR, where the number of \fIy\fR's is determined by
 404 the precision (default: 6).
 405 If the precision is 0 then no decimal point is output.
 406 .TP 10
 407 \fBe\fR or \fBe\fR
 408 Convert floating-point number to scientific notation in the
 409 form \fIx.yyy\fBe\(+-\fIzz\fR, where the number of \fIy\fR's is determined
 410 by the precision (default: 6).
 411 If the precision is 0 then no decimal point is output.
 412 If the \fBE\fR form is used then \fBE\fR is
 413 printed instead of \fBe\fR.
 414 .TP 10
 415 \fBg\fR or \fBG\fR
 416 If the exponent is less than \-4 or greater than or equal to the
 417 precision, then convert floating-point number as for \fB%e\fR or
 418 \fB%E\fR.
 419 Otherwise convert as for \fB%f\fR.
 420 Trailing zeroes and a trailing decimal point are omitted.
 421 .TP 10
 422 \fB%\fR
 423 No conversion: just insert \fB%\fR.
 424 .LP
 425 For the numerical conversions the argument being converted must
 426 be an integer or floating-point string; format converts the argument
 427 to binary and then converts it back to a string according to
 428 the conversion specifier.
 429
 430 .SH "DIFFERENCES FROM ANSI SPRINTF"
 431 .PP
 432 The behavior of the format command is the same as the
 433 ANSI C \fBsprintf\fR procedure except for the following
 434 differences:
 435 .IP [1]
 436 \fB%p\fR and \fB%n\fR specifiers are not currently supported.
 437 .IP [2]
 438 For \fB%c\fR conversions the argument must be a decimal string,
 439 which will then be converted to the corresponding character value.
 440 .IP [3]
 441 The \fBl\fR modifier is ignored;  integer values are always converted
 442 as if there were no modifier present and real values are always
 443 converted as if the \fBl\fR modifier were present (i.e. type
 444 \fBdouble\fR is used for the internal representation).
 445 If the \fBh\fR modifier is specified then integer values are truncated
 446 to \fBshort\fR before conversion.
 447
 448 .SH "SEE ALSO"
 449 sprintf(3), string(n)
 450
 451 .SH KEYWORDS
 452 conversion specifier, format, sprintf, string, substitution