raw/mann/tclvars.n

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  10 '\" The definitions below are for supplemental macros used in Tcl/Tk
  11 '\" manual entries.
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  61 '\"
  62 '\" .OP cmdName dbName dbClass
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  64 '\"     option's name as specified in the class command, dbName gives
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 208 .SH "STANDARD OPTIONS"
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 211 .ta 5.5c 11c
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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.
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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
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 245 ..
 246 .TH tclvars n 8.0 Tcl "Tcl Built-In Commands"
 247 .BS
 248 '\" Note:  do not modify the .SH NAME line immediately below!
 249 .SH NAME
 250 tclvars \- Variables used by Tcl
 251 .BE
 252
 253 .SH DESCRIPTION
 254 .PP
 255 The following global variables are created and managed automatically
 256 by the Tcl library.  Except where noted below, these variables should
 257 normally be treated as read-only by application-specific code and by users.
 258 .TP
 259 \fBenv\fR
 260 This variable is maintained by Tcl as an array
 261 whose elements are the environment variables for the process.
 262 Reading an element will return the value of the corresponding
 263 environment variable.
 264 Setting an element of the array will modify the corresponding
 265 environment variable or create a new one if it doesn't already
 266 exist.
 267 Unsetting an element of \fBenv\fR will remove the corresponding
 268 environment variable.
 269 Changes to the \fBenv\fR array will affect the environment
 270 passed to children by commands like \fBexec\fR.
 271 If the entire \fBenv\fR array is unset then Tcl will stop
 272 monitoring \fBenv\fR accesses and will not update environment
 273 variables.
 274 .RS
 275 .VS 8.0
 276 Under Windows, the environment variables PATH and COMSPEC in any
 277 capitalization are converted automatically to upper case.  For instance, the
 278 PATH variable could be exported by the operating system as ``path'',
 279 ``Path'', ``PaTh'', etc., causing otherwise simple Tcl code to have to
 280 support many special cases.  All other environment variables inherited by
 281 Tcl are left unmodified.
 282 .VE
 283 .RE
 284 .RS
 285 On the Macintosh, the environment variable is constructed by Tcl as no
 286 global environment variable exists.  The environment variables that
 287 are created for Tcl include:
 288 .TP
 289 \fBLOGIN\fR
 290 This holds the Chooser name of the Macintosh.
 291 .TP
 292 \fBUSER\fR
 293 This also holds the Chooser name of the Macintosh.
 294 .TP
 295 \fBSYS_FOLDER\fR
 296 The path to the system directory.
 297 .TP
 298 \fBAPPLE_M_FOLDER\fR
 299 The path to the Apple Menu directory.
 300 .TP
 301 \fBCP_FOLDER\fR
 302 The path to the control panels directory.
 303 .TP
 304 \fBDESK_FOLDER\fR
 305 The path to the desk top directory.
 306 .TP
 307 \fBEXT_FOLDER\fR
 308 The path to the system extensions directory.
 309 .TP
 310 \fBPREF_FOLDER\fR
 311 The path to the preferences directory.
 312 .TP
 313 \fBPRINT_MON_FOLDER\fR
 314 The path to the print monitor directory.
 315 .TP
 316 \fBSHARED_TRASH_FOLDER\fR
 317 The path to the network trash directory.
 318 .TP
 319 \fBTRASH_FOLDER\fR
 320 The path to the trash directory.
 321 .TP
 322 \fBSTART_UP_FOLDER\fR
 323 The path to the start up directory.
 324 .TP
 325 \fBHOME\fR
 326 The path to the application's default directory.
 327 .PP
 328 You can also create your own environment variables for the Macintosh.
 329 A file named  \fITcl Environment Variables\fR may be placed in the
 330 preferences folder in the Mac system folder.  Each line of this file
 331 should be of the form \fIVAR_NAME=var_data\fR.
 332 .PP
 333 The last alternative is to place environment variables in a 'STR#'
 334 resource named \fITcl Environment Variables\fR of the application.  This
 335 is considered a little more ``Mac like'' than a Unix style Environment
 336 Variable file.  Each entry in the 'STR#' resource has the same format
 337 as above.  The source code file \fItclMacEnv.c\fR contains the
 338 implementation of the env mechanisms.  This file contains many
 339 #define's that allow customization of the env mechanisms to fit your
 340 applications needs.
 341 .RE
 342 .TP
 343 \fBerrorCode\fR
 344 After an error has occurred, this variable will be set to hold
 345 additional information about the error in a form that is easy
 346 to process with programs.
 347 \fBerrorCode\fR consists of a Tcl list with one or more elements.
 348 The first element of the list identifies a general class of
 349 errors, and determines the format of the rest of the list.
 350 The following formats for \fBerrorCode\fR are used by the
 351 Tcl core; individual applications may define additional formats.
 352 .RS
 353 .TP
 354 \fBARITH\fI code msg\fR
 355 This format is used when an arithmetic error occurs (e.g. an attempt
 356 to divide by zero in the \fBexpr\fR command).
 357 \fICode\fR identifies the precise error and \fImsg\fR provides a
 358 human-readable description of the error.  \fICode\fR will be either
 359 DIVZERO (for an attempt to divide by zero),
 360 DOMAIN (if an argument is outside the domain of a function, such as acos(\-3)),
 361 IOVERFLOW (for integer overflow),
 362 OVERFLOW (for a floating-point overflow),
 363 or UNKNOWN (if the cause of the error cannot be determined).
 364 .TP
 365 \fBCHILDKILLED\fI pid sigName msg\fR
 366 This format is used when a child process has been killed because of
 367 a signal.  The second element of \fBerrorCode\fR will be the
 368 process's identifier (in decimal).
 369 The third element will be the symbolic name of the signal that caused
 370 the process to terminate; it will be one of the names from the
 371 include file signal.h, such as \fBSIGPIPE\fR.
 372 The fourth element will be a short human-readable message
 373 describing the signal, such as ``write on pipe with no readers''
 374 for \fBSIGPIPE\fR.
 375 .TP
 376 \fBCHILDSTATUS\fI pid code\fR
 377 This format is used when a child process has exited with a non-zero
 378 exit status.  The second element of \fBerrorCode\fR will be the
 379 process's identifier (in decimal) and the third element will be the exit
 380 code returned by the process (also in decimal).
 381 .TP
 382 \fBCHILDSUSP\fI pid sigName msg\fR
 383 This format is used when a child process has been suspended because
 384 of a signal.
 385 The second element of \fBerrorCode\fR will be the process's identifier,
 386 in decimal.
 387 The third element will be the symbolic name of the signal that caused
 388 the process to suspend; this will be one of the names from the
 389 include file signal.h, such as \fBSIGTTIN\fR.
 390 The fourth element will be a short human-readable message
 391 describing the signal, such as ``background tty read''
 392 for \fBSIGTTIN\fR.
 393 .TP
 394 \fBNONE\fR
 395 This format is used for errors where no additional information is
 396 available for an error besides the message returned with the
 397 error.  In these cases \fBerrorCode\fR will consist of a list
 398 containing a single element whose contents are \fBNONE\fR.
 399 .TP
 400 \fBPOSIX \fIerrName msg\fR
 401 If the first element of \fBerrorCode\fR is \fBPOSIX\fR, then
 402 the error occurred during a POSIX kernel call.
 403 The second element of the list will contain the symbolic name
 404 of the error that occurred, such as \fBENOENT\fR; this will
 405 be one of the values defined in the include file errno.h.
 406 The third element of the list will be a human-readable
 407 message corresponding to \fIerrName\fR, such as
 408 ``no such file or directory'' for the \fBENOENT\fR case.
 409 .PP
 410 To set \fBerrorCode\fR, applications should use library
 411 procedures such as \fBTcl_SetErrorCode\fR and \fBTcl_PosixError\fR,
 412 or they may invoke the \fBerror\fR command.
 413 If one of these methods hasn't been used, then the Tcl
 414 interpreter will reset the variable to \fBNONE\fR after
 415 the next error.
 416 .RE
 417 .TP
 418 \fBerrorInfo\fR
 419 After an error has occurred, this string will contain one or more lines
 420 identifying the Tcl commands and procedures that were being executed
 421 when the most recent error occurred.
 422 Its contents take the form of a stack trace showing the various
 423 nested Tcl commands that had been invoked at the time of the error.
 424 .TP
 425 \fBtcl_library\fR
 426 This variable holds the name of a directory containing the
 427 system library of Tcl scripts, such as those used for auto-loading.
 428 The value of this variable is returned by the \fBinfo library\fR command.
 429 See the \fBlibrary\fR manual entry for details of the facilities
 430 provided by the Tcl script library.
 431 Normally each application or package will have its own application-specific
 432 script library in addition to the Tcl script library;
 433 each application should set a global variable with a name like
 434 \fB$\fIapp\fB_library\fR (where \fIapp\fR is the application's name)
 435 to hold the network file name for that application's library directory.
 436 The initial value of \fBtcl_library\fR is set when an interpreter
 437 is created by searching several different directories until one is
 438 found that contains an appropriate Tcl startup script.
 439 If the \fBTCL_LIBRARY\fR environment variable exists, then
 440 the directory it names is checked first.
 441 If \fBTCL_LIBRARY\fR isn't set or doesn't refer to an appropriate
 442 directory, then Tcl checks several other directories based on a
 443 compiled-in default location, the location of the binary containing
 444 the application, and the current working directory.
 445 .TP
 446 \fBtcl_patchLevel\fR
 447 When an interpreter is created Tcl initializes this variable to
 448 hold a string giving the current patch level for Tcl, such as
 449 \fB7.3p2\fR for Tcl 7.3 with the first two official patches, or
 450 \fB7.4b4\fR for the fourth beta release of Tcl 7.4.
 451 The value of this variable is returned by the \fBinfo patchlevel\fR
 452 command.
 453 .VS 8.0 br
 454 .TP
 455 \fBtcl_pkgPath\fR
 456 This variable holds a list of directories indicating where packages are
 457 normally installed.  It is not used on Windows.  It typically contains
 458 either one or two entries; if it contains two entries, the first is
 459 normally a directory for platform-dependent packages (e.g., shared library
 460 binaries) and the second is normally a directory for platform-independent
 461 packages (e.g., script files). Typically a package is installed as a
 462 subdirectory of one of the entries in \fB$tcl_pkgPath\fR. The directories
 463 in \fB$tcl_pkgPath\fR are included by default in the \fBauto_path\fR
 464 variable, so they and their immediate subdirectories are automatically
 465 searched for packages during \fBpackage require\fR commands.  Note:
 466 \fBtcl_pkgPath\fR it not intended to be modified by the application.  Its
 467 value is added to \fBauto_path\fR at startup; changes to \fBtcl_pkgPath\fR
 468 are not reflected in \fBauto_path\fR.  If you want Tcl to search additional
 469 directories for packages you should add the names of those directories to
 470 \fBauto_path\fR, not \fBtcl_pkgPath\fR.
 471 .VE
 472 .TP
 473 \fBtcl_platform\fR
 474 This is an associative array whose elements contain information about
 475 the platform on which the application is running, such as the name of
 476 the operating system, its current release number, and the machine's
 477 instruction set.  The elements listed below will always
 478 be defined, but they may have empty strings as values if Tcl couldn't
 479 retrieve any relevant information.  In addition, extensions
 480 and applications may add additional values to the array.  The
 481 predefined elements are:
 482
 483
 484
 485
 486
 487 .RS
 488 .VS
 489 .TP
 490 \fBbyteOrder\fR
 491 The native byte order of this machine: either \fBlittleEndian\fR or
 492 \fBbigEndian\fR.
 493 .VE
 494 .TP
 495 \fBdebug\fR
 496 If this variable exists, then the interpreter
 497 was compiled with debugging symbols enabled.  This varible will only
 498 exist on Windows so extension writers can specify which package to load
 499 depending on the C run-time library that is loaded.
 500 .TP
 501 \fBmachine\fR
 502 The instruction set executed by this machine, such as
 503 \fBintel\fR, \fBPPC\fR, \fB68k\fR, or \fBsun4m\fR.  On UNIX machines, this
 504 is the value returned by \fBuname -m\fR.
 505 .TP
 506 \fBos\fR
 507 The name of the operating system running on this machine,
 508 such as \fBWindows 95\fR, \fBWindows NT\fR, \fBMacOS\fR, or \fBSunOS\fR.
 509 On UNIX machines, this is the value returned by \fBuname -s\fR.
 510 On Windows 95 and Windows 98, the value returned will be \fBWindows
 511 95\fR to provide better backwards compatibility to Windows 95; to
 512 distinguish between the two, check the \fBosVersion\fR.
 513 .TP
 514 \fBosVersion\fR
 515 The version number for the operating system running on this machine.
 516 On UNIX machines, this is the value returned by \fBuname -r\fR.  On
 517 Windows 95, the version will be 4.0; on Windows 98, the version will
 518 be 4.10.
 519 .TP
 520 \fBplatform\fR
 521 Either \fBwindows\fR, \fBmacintosh\fR, or \fBunix\fR.  This identifies the
 522 general operating environment of the machine.
 523 .TP
 524 \fBthreaded\fR
 525 If this variable exists, then the interpreter
 526 was compiled with threads enabled.
 527 .TP
 528 \fBuser\fR
 529 This identifies the
 530 current user based on the login information available on the platform.
 531 This comes from the USER or LOGNAME environment variable on Unix,
 532 and the value from GetUserName on Windows and Macintosh.
 533 .RE
 534 .TP
 535 \fBtcl_precision\fR
 536 .VS
 537 This variable controls the number of digits to generate
 538 when converting floating-point values to strings.  It defaults
 539 to 12.
 540 17 digits is ``perfect'' for IEEE floating-point in that it allows
 541 double-precision values to be converted to strings and back to
 542 binary with no loss of information.  However, using 17 digits prevents
 543 any rounding, which produces longer, less intuitive results.  For example,
 544 \fBexpr 1.4\fR returns 1.3999999999999999 with \fBtcl_precision\fR
 545 set to 17, vs. 1.4 if \fBtcl_precision\fR is 12.
 546 .RS
 547 All interpreters in a process share a single \fBtcl_precision\fR value:
 548 changing it in one interpreter will affect all other interpreters as
 549 well.  However, safe interpreters are not allowed to modify the
 550 variable.
 551 .RE
 552 .VE
 553 .TP
 554 \fBtcl_rcFileName\fR
 555 This variable is used during initialization to indicate the name of a
 556 user-specific startup file.  If it is set by application-specific
 557 initialization, then the Tcl startup code will check for the existence
 558 of this file and \fBsource\fR it if it exists.  For example, for \fBwish\fR
 559 the variable is set to \fB~/.wishrc\fR for Unix and \fB~/wishrc.tcl\fR
 560 for Windows.
 561 .TP
 562 \fBtcl_rcRsrcName\fR
 563 This variable is only used on Macintosh systems.  The variable is used
 564 during initialization to indicate the name of a user-specific
 565 \fBTEXT\fR resource located in the application or extension resource
 566 forks.  If it is set by application-specific initialization, then the
 567 Tcl startup code will check for the existence of this resource and
 568 \fBsource\fR it if it exists.  For example, the Macintosh \fBwish\fR
 569 application has the variable is set to \fBtclshrc\fR.
 570 .TP
 571 \fBtcl_traceCompile\fR
 572 The value of this variable can be set to control
 573 how much tracing information
 574 is displayed during bytecode compilation.
 575 By default, tcl_traceCompile is zero and no information is displayed.
 576 Setting tcl_traceCompile to 1 generates a one line summary in stdout
 577 whenever a procedure or top level command is compiled.
 578 Setting it to 2 generates a detailed listing in stdout of the
 579 bytecode instructions emitted during every compilation.
 580 This variable is useful in
 581 tracking down suspected problems with the Tcl compiler.
 582 It is also occasionally useful when converting
 583 existing code to use Tcl8.0.
 584 .TP
 585 \fBtcl_traceExec\fR
 586 The value of this variable can be set to control
 587 how much tracing information
 588 is displayed during bytecode execution.
 589 By default, tcl_traceExec is zero and no information is displayed.
 590 Setting tcl_traceExec to 1 generates a one line trace in stdout
 591 on each call to a Tcl procedure.
 592 Setting it to 2 generates a line of output
 593 whenever any Tcl command is invoked
 594 that contains the name of the command and its arguments.
 595 Setting it to 3 produces a detailed trace showing the result of
 596 executing each bytecode instruction.
 597 Note that when tcl_traceExec is 2 or 3,
 598 commands such as set and incr
 599 that have been entirely replaced by a sequence
 600 of bytecode instructions are not shown.
 601 Setting this variable is useful in
 602 tracking down suspected problems with the bytecode compiler
 603 and interpreter.
 604 It is also occasionally useful when converting
 605 code to use Tcl8.0.
 606 .TP
 607 \fBtcl_wordchars\fR
 608 The value of this variable is a regular expression that can be set to
 609 control what are considered ``word'' characters, for instances like
 610 selecting a word by double-clicking in text in Tk.  It is platform
 611 dependent.  On Windows, it defaults to \fB\\S\fR, meaning anything
 612 but a Unicode space character.  Otherwise it defaults to \fB\\w\fR,
 613 which is any Unicode word character (number, letter, or underscore).
 614 .TP
 615 \fBtcl_nonwordchars\fR
 616 The value of this variable is a regular expression that can be set to
 617 control what are considered ``non-word'' characters, for instances like
 618 selecting a word by double-clicking in text in Tk.  It is platform
 619 dependent.  On Windows, it defaults to \fB\\s\fR, meaning any Unicode space
 620 character.  Otherwise it defaults to \fB\\W\fR, which is anything but a
 621 Unicode word character (number, letter, or underscore).
 622 .TP
 623 \fBtcl_version\fR
 624 When an interpreter is created Tcl initializes this variable to
 625 hold the version number for this version of Tcl in the form \fIx.y\fR.
 626 Changes to \fIx\fR represent major changes with probable
 627 incompatibilities and changes to \fIy\fR represent small enhancements and
 628 bug fixes that retain backward compatibility.
 629 The value of this variable is returned by the \fBinfo tclversion\fR
 630 command.
 631
 632 .SH "SEE ALSO"
 633 eval(n)
 634
 635 .SH KEYWORDS
 636 arithmetic, bytecode, compiler, error, environment, POSIX, precision, subprocess, variables