Manual Pages for UNIX Darwin command on man tclvars

tclvars(n) Tcl Built-In Commands tclvars(n)

NAME

tclvars - Variables used by Tcl

DESCRIPTION

The following global variables are created and managed automatically by

the Tcl library. Except where noted below, these variables should nor-

mally be treated as read-only by application-specific code and by

users. eennvv This variable is maintained by Tcl as an array whose elements

are the environment variables for the process. Reading an ele-

ment will return the value of the corresponding environment

variable. Setting an element of the array will modify the cor-

responding environment variable or create a new one if it doesn't already exist. Unsetting an element of eennvv will remove the corresponding environment variable. Changes to the eennvv array will affect the environment passed to children by commands like eexxeecc. If the entire eennvv array is unset then Tcl will stop

monitoring eennvv accesses and will not update environment vari-

ables. Under Windows, the environment variables PATH and COMSPEC in any | capitalization are converted automatically to upper case. For | instance, the PATH variable could be exported by the operating | system as ``path'', ``Path'', ``PaTh'', etc., causing otherwise | simple Tcl code to have to support many special cases. All |

other environment variables inherited by Tcl are left unmodi- |

fied. Setting an env array variable to blank is the same as | unsetting it as this is the behavior of the underlying Windows | OS. It should be noted that relying on an existing and empty | environment variable won't work on windows and is discouraged |

for cross-platform usage.

On the Macintosh, the environment variable is constructed by Tcl

as no global environment variable exists. The environment vari-

ables that are created for Tcl include: LLOOGGIINN This holds the Chooser name of the Macintosh. UUSSEERR This also holds the Chooser name of the Macintosh. SSYYSSFFOOLLDDEERR The path to the system directory. AAPPPPLLEEMMFFOOLLDDEERR The path to the Apple Menu directory. CCPPFFOOLLDDEERR The path to the control panels directory. DDEESSKKFFOOLLDDEERR The path to the desk top directory. EEXXTTFFOOLLDDEERR The path to the system extensions directory. PPRREEFFFFOOLLDDEERR The path to the preferences directory. PPRRIINNTTMMOONNFFOOLLDDEERR The path to the print monitor directory. SSHHAARREEDDTTRRAASSHHFFOOLLDDEERR The path to the network trash directory. TTRRAASSHHFFOOLLDDEERR The path to the trash directory. SSTTAARRTTUUPPFFOOLLDDEERR The path to the start up directory. HHOOMMEE The path to the application's default directory.

You can also create your own environment variables for the Mac-

intosh. A file named Tcl Environment Variables may be placed in the preferences folder in the Mac system folder. Each line

of this file should be of the form VARNAME=vardata.

The last alternative is to place environment variables in a

'STR#' resource named Tcl Environment Variables of the applica-

tion. This is considered a little more ``Mac like'' than a Unix

style Environment Variable file. Each entry in the 'STR#'

resource has the same format as above. The source code file tclMacEnv.c contains the implementation of the env mechanisms.

This file contains many #define's that allow customization of

the env mechanisms to fit your applications needs. eerrrroorrCCooddee After an error has occurred, this variable will be set to hold additional information about the error in a form that is easy to process with programs. eerrrroorrCCooddee consists of a Tcl list with one or more elements. The first element of the list identifies a general class of errors, and determines the format of the rest of the list. The following formats for eerrrroorrCCooddee are used by

the Tcl core; individual applications may define additional for-

mats. AARRIITTHH code msg This format is used when an arithmetic error occurs (e.g. an attempt to divide by zero in the eexxpprr command). Code

identifies the precise error and msg provides a human-

readable description of the error. Code will be either DIVZERO (for an attempt to divide by zero), DOMAIN (if an argument is outside the domain of a function, such as

acos(-3)), IOVERFLOW (for integer overflow), OVERFLOW

(for a floating-point overflow), or UNKNOWN (if the cause

of the error cannot be determined). CCHHIILLDDKKIILLLLEEDD pid sigName msg This format is used when a child process has been killed because of a signal. The second element of eerrrroorrCCooddee will be the process's identifier (in decimal). The third element will be the symbolic name of the signal that caused the process to terminate; it will be one of the names from the include file signal.h, such as SSIIGGPPIIPPEE.

The fourth element will be a short human-readable message

describing the signal, such as ``write on pipe with no readers'' for SSIIGGPPIIPPEE. CCHHIILLDDSSTTAATTUUSS pid code This format is used when a child process has exited with

a non-zero exit status. The second element of eerrrroorrCCooddee

will be the process's identifier (in decimal) and the third element will be the exit code returned by the process (also in decimal). CCHHIILLDDSSUUSSPP pid sigName msg

This format is used when a child process has been sus-

pended because of a signal. The second element of eerrrroorr-

CCooddee will be the process's identifier, in decimal. The third element will be the symbolic name of the signal that caused the process to suspend; this will be one of

the names from the include file signal.h, such as SSIIGGTT-

TTIINN. The fourth element will be a short human-readable

message describing the signal, such as ``background tty read'' for SSIIGGTTTTIINN.

NNOONNEE This format is used for errors where no additional infor-

mation is available for an error besides the message returned with the error. In these cases eerrrroorrCCooddee will

consist of a list containing a single element whose con-

tents are NNOONNEE. PPOOSSIIXX errName msg If the first element of eerrrroorrCCooddee is PPOOSSIIXX, then the error occurred during a POSIX kernel call. The second element of the list will contain the symbolic name of the error that occurred, such as EENNOOEENNTT; this will be one of the values defined in the include file errno.h. The

third element of the list will be a human-readable mes-

sage corresponding to errName, such as ``no such file or directory'' for the EENNOOEENNTT case. To set eerrrroorrCCooddee, applications should use library procedures such as TTccllSSeettEErrrroorrCCooddee and TTccllPPoossiixxEErrrroorr, or they may invoke the eerrrroorr command. If one of these methods hasn't been used, then the Tcl interpreter will reset the variable to NNOONNEE after the next error. eerrrroorrIInnffoo After an error has occurred, this string will contain one or more lines identifying the Tcl commands and procedures that were

being executed when the most recent error occurred. Its con-

tents take the form of a stack trace showing the various nested Tcl commands that had been invoked at the time of the error. ttcclllliibbrraarryy

This variable holds the name of a directory containing the sys-

tem library of Tcl scripts, such as those used for auto-loading.

The value of this variable is returned by the iinnffoo lliibbrraarryy com-

mand. See the lliibbrraarryy manual entry for details of the facili-

ties provided by the Tcl script library. Normally each applica-

tion or package will have its own application-specific script

library in addition to the Tcl script library; each application

should set a global variable with a name like $$applliibbrraarryy

(where app is the application's name) to hold the network file name for that application's library directory. The initial value of ttcclllliibbrraarryy is set when an interpreter is created by searching several different directories until one is found that contains an appropriate Tcl startup script. If the TTCCLLLLIIBBRRAARRYY environment variable exists, then the directory it names is checked first. If TTCCLLLLIIBBRRAARRYY isn't set or doesn't refer to an appropriate directory, then Tcl checks several other directories

based on a compiled-in default location, the location of the

binary containing the application, and the current working directory. ttccllppaattcchhLLeevveell When an interpreter is created Tcl initializes this variable to hold a string giving the current patch level for Tcl, such as 77..33pp22 for Tcl 7.3 with the first two official patches, or 77..44bb44

for the fourth beta release of Tcl 7.4. The value of this vari-

able is returned by the iinnffoo ppaattcchhlleevveell command.

ttccllppkkgg- |

PPaatthh | |

This variable holds a list of directories indicating where pack- |

ages are normally installed. It is not used on Windows. It | typically contains either one or two entries; if it contains two |

entries, the first is normally a directory for platform-depen- |

dent packages (e.g., shared library binaries) and the second is |

normally a directory for platform-independent packages (e.g., |

script files). Typically a package is installed as a subdirec- |

tory of one of the entries in $$ttccllppkkggPPaatthh. The directories in |

$$ttccllppkkggPPaatthh are included by default in the aauuttooppaatthh variable, |

so they and their immediate subdirectories are automatically | searched for packages during ppaacckkaaggee rreeqquuiirree commands. Note: | ttccllppkkggPPaatthh it not intended to be modified by the application. |

Its value is added to aauuttooppaatthh at startup; changes to ttccllppkkgg- |

PPaatthh are not reflected in aauuttooppaatthh. If you want Tcl to search | additional directories for packages you should add the names of | those directories to aauuttooppaatthh, not ttccllppkkggPPaatthh. ttccllppllaattffoorrmm This is an associative array whose elements contain information about the platform on which the application is running, such as the name of the operating system, its current release number, and the machine's instruction set. The elements listed below

will always be defined, but they may have empty strings as val-

ues if Tcl couldn't retrieve any relevant information. In addi-

tion, extensions and applications may add additional values to the array. The predefined elements are:

bbyyttee- |

OOrrddeerr | |

The native byte order of this machine: either lliittttlleeEEnn- |

ddiiaann or bbiiggEEnnddiiaann.

ddeebbuugg If this variable exists, then the interpreter was com-

piled with debugging symbols enabled. This variable will only exist on Windows so extension writers can specify

which package to load depending on the C run-time library

that is loaded. mmaacchhiinnee The instruction set executed by this machine, such as iinntteell, PPPPCC, 6688kk, or ssuunn44mm. On UNIX machines, this is the

value returned by uunnaammee -mm.

ooss The name of the operating system running on this machine, such as WWiinnddoowwss 9955, WWiinnddoowwss NNTT, MMaaccOOSS, or SSuunnOOSS. On UNIX

machines, this is the value returned by uunnaammee -ss. On

Windows 95 and Windows 98, the value returned will be WWiinnddoowwss 9955 to provide better backwards compatibility to Windows 95; to distinguish between the two, check the oossVVeerrssiioonn. oossVVeerrssiioonn The version number for the operating system running on this machine. On UNIX machines, this is the value

returned by uunnaammee -rr. On Windows 95, the version will be

4.0; on Windows 98, the version will be 4.10. ppllaattffoorrmm Either wwiinnddoowwss, mmaacciinnttoosshh, or uunniixx. This identifies the general operating environment of the machine. tthhrreeaaddeedd

If this variable exists, then the interpreter was com-

piled with threads enabled. uusseerr This identifies the current user based on the login information available on the platform. This comes from

the USER or LOGNAME environment variable on Unix, and the

value from GetUserName on Windows and Macintosh. wwoorrddSSiizzee

This gives the size of the native-machine word in bytes |

(strictly, it is same as the result of evaluating | sizeof(long) in C.) ttccllpprreecciissiioonn This variable controls the number of digits to generate when |

converting floating-point values to strings. It defaults to 12. |

17 digits is ``perfect'' for IEEE floating-point in that it |

allows double-precision values to be converted to strings and |

back to binary with no loss of information. However, using 17 |

digits prevents any rounding, which produces longer, less intu- |

itive results. For example, eexxpprr 11..44 returns 1.3999999999999999 | with ttccllpprreecciissiioonn set to 17, vs. 1.4 if ttccllpprreecciissiioonn is 12. | All interpreters in a process share a single ttccllpprreecciissiioonn | value: changing it in one interpreter will affect all other | interpreters as well. However, safe interpreters are not | allowed to modify the variable. | ttccllrrccFFiilleeNNaammee This variable is used during initialization to indicate the name

of a user-specific startup file. If it is set by application-

specific initialization, then the Tcl startup code will check for the existence of this file and ssoouurrccee it if it exists. For example, for wwiisshh the variable is set to ~~//..wwiisshhrrcc for Unix and ~~//wwiisshhrrcc..ttccll for Windows. ttccllrrccRRssrrccNNaammee This variable is only used on Macintosh systems. The variable

is used during initialization to indicate the name of a user-

specific TTEEXXTT resource located in the application or extension

resource forks. If it is set by application-specific initial-

ization, then the Tcl startup code will check for the existence of this resource and ssoouurrccee it if it exists. For example, the Macintosh wwiisshh application has the variable is set to ttccllsshhrrcc. ttccllttrraacceeCCoommppiillee

The value of this variable can be set to control how much trac-

ing information is displayed during bytecode compilation. By

default, tcltraceCompile is zero and no information is dis-

played. Setting tcltraceCompile to 1 generates a one line sum-

mary in stdout whenever a procedure or top level command is com-

piled. Setting it to 2 generates a detailed listing in stdout of the bytecode instructions emitted during every compilation. This variable is useful in tracking down suspected problems with

the Tcl compiler. It is also occasionally useful when convert-

ing existing code to use Tcl8.0. This variable and functionality only exist if TCLCOMPILEDEBUG was defined during Tcl's compilation. ttccllttrraacceeEExxeecc

The value of this variable can be set to control how much trac-

ing information is displayed during bytecode execution. By default, tcltraceExec is zero and no information is displayed. Setting tcltraceExec to 1 generates a one line trace in stdout on each call to a Tcl procedure. Setting it to 2 generates a line of output whenever any Tcl command is invoked that contains

the name of the command and its arguments. Setting it to 3 pro-

duces a detailed trace showing the result of executing each bytecode instruction. Note that when tcltraceExec is 2 or 3, commands such as set and incr that have been entirely replaced by a sequence of bytecode instructions are not shown. Setting this variable is useful in tracking down suspected problems with the bytecode compiler and interpreter. It is also occasionally useful when converting code to use Tcl8.0. This variable and functionality only exist if TCLCOMPILEDEBUG was defined during Tcl's compilation. ttccllwwoorrddcchhaarrss The value of this variable is a regular expression that can be set to control what are considered ``word'' characters, for

instances like selecting a word by double-clicking in text in

Tk. It is platform dependent. On Windows, it defaults to \\SS, meaning anything but a Unicode space character. Otherwise it defaults to \\ww, which is any Unicode word character (number, letter, or underscore). ttccllnnoonnwwoorrddcchhaarrss The value of this variable is a regular expression that can be

set to control what are considered ``non-word'' characters, for

instances like selecting a word by double-clicking in text in

Tk. It is platform dependent. On Windows, it defaults to \\ss, meaning any Unicode space character. Otherwise it defaults to

\\WW, which is anything but a Unicode word character (number, let-

ter, or underscore). ttccllvveerrssiioonn When an interpreter is created Tcl initializes this variable to hold the version number for this version of Tcl in the form x.y.

Changes to x represent major changes with probable incompatibil-

ities and changes to y represent small enhancements and bug fixes that retain backward compatibility. The value of this variable is returned by the iinnffoo ttccllvveerrssiioonn command.