[25] | 1 | '\" |
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| 2 | '\" Copyright (c) 1993 The Regents of the University of California. |
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| 3 | '\" Copyright (c) 1994-1997 Sun Microsystems, Inc. |
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| 4 | '\" |
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| 5 | '\" See the file "license.terms" for information on usage and redistribution |
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| 6 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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| 7 | '\" |
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| 8 | '\" RCS: @(#) $Id: tclvars.n,v 1.35 2007/12/13 15:22:33 dgp Exp $ |
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| 9 | '\" |
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| 10 | .so man.macros |
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| 11 | .TH tclvars n 8.0 Tcl "Tcl Built-In Commands" |
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| 12 | .BS |
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| 13 | '\" Note: do not modify the .SH NAME line immediately below! |
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| 14 | .SH NAME |
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| 15 | tclvars \- Variables used by Tcl |
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| 16 | .BE |
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| 17 | .SH DESCRIPTION |
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| 18 | .PP |
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| 19 | The following global variables are created and managed automatically |
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| 20 | by the Tcl library. Except where noted below, these variables should |
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| 21 | normally be treated as read-only by application-specific code and by users. |
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| 22 | .TP |
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| 23 | \fBenv\fR |
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| 24 | This variable is maintained by Tcl as an array |
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| 25 | whose elements are the environment variables for the process. |
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| 26 | Reading an element will return the value of the corresponding |
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| 27 | environment variable. |
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| 28 | Setting an element of the array will modify the corresponding |
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| 29 | environment variable or create a new one if it does not already |
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| 30 | exist. |
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| 31 | Unsetting an element of \fBenv\fR will remove the corresponding |
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| 32 | environment variable. |
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| 33 | Changes to the \fBenv\fR array will affect the environment |
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| 34 | passed to children by commands like \fBexec\fR. |
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| 35 | If the entire \fBenv\fR array is unset then Tcl will stop |
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| 36 | monitoring \fBenv\fR accesses and will not update environment |
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| 37 | variables. |
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| 38 | .RS |
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| 39 | .PP |
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| 40 | Under Windows, the environment variables PATH and COMSPEC in any |
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| 41 | capitalization are converted automatically to upper case. For instance, the |
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| 42 | PATH variable could be exported by the operating system as |
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| 43 | .QW path , |
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| 44 | .QW Path , |
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| 45 | .QW PaTh , |
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| 46 | etc., causing otherwise simple Tcl code to have to |
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| 47 | support many special cases. All other environment variables inherited by |
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| 48 | Tcl are left unmodified. Setting an env array variable to blank is the |
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| 49 | same as unsetting it as this is the behavior of the underlying Windows OS. |
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| 50 | It should be noted that relying on an existing and empty environment variable |
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| 51 | will not work on Windows and is discouraged for cross-platform usage. |
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| 52 | .RE |
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| 53 | .TP |
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| 54 | \fBerrorCode\fR |
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| 55 | This variable holds the value of the \fB\-errorcode\fR return option |
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| 56 | set by the most recent error that occurred in this interpreter. |
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| 57 | This list value represents additional information about the error |
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| 58 | in a form that is easy to process with programs. |
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| 59 | The first element of the list identifies a general class of |
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| 60 | errors, and determines the format of the rest of the list. |
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| 61 | The following formats for \fB\-errorcode\fR return options |
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| 62 | are used by the Tcl core; individual applications may define |
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| 63 | additional formats. |
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| 64 | .RS |
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| 65 | .TP |
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| 66 | \fBARITH\fI code msg\fR |
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| 67 | . |
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| 68 | This format is used when an arithmetic error occurs (e.g. an attempt |
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| 69 | to divide zero by zero in the \fBexpr\fR command). |
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| 70 | \fICode\fR identifies the precise error and \fImsg\fR provides a |
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| 71 | human-readable description of the error. \fICode\fR will be either |
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| 72 | DIVZERO (for an attempt to divide by zero), |
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| 73 | DOMAIN (if an argument is outside the domain of a function, such as acos(\-3)), |
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| 74 | IOVERFLOW (for integer overflow), |
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| 75 | OVERFLOW (for a floating-point overflow), |
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| 76 | or UNKNOWN (if the cause of the error cannot be determined). |
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| 77 | .RS |
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| 78 | .PP |
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| 79 | Detection of these errors depends in part on the underlying hardware |
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| 80 | and system libraries. |
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| 81 | .RE |
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| 82 | .TP |
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| 83 | \fBCHILDKILLED\fI pid sigName msg\fR |
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| 84 | This format is used when a child process has been killed because of |
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| 85 | a signal. The \fIpid\fR element will be the process's identifier (in decimal). |
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| 86 | The \fIsigName\fR element will be the symbolic name of the signal that caused |
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| 87 | the process to terminate; it will be one of the names from the |
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| 88 | include file signal.h, such as \fBSIGPIPE\fR. |
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| 89 | The \fImsg\fR element will be a short human-readable message |
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| 90 | describing the signal, such as |
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| 91 | .QW "write on pipe with no readers" |
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| 92 | for \fBSIGPIPE\fR. |
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| 93 | .TP |
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| 94 | \fBCHILDSTATUS\fI pid code\fR |
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| 95 | This format is used when a child process has exited with a non-zero |
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| 96 | exit status. The \fIpid\fR element will be the |
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| 97 | process's identifier (in decimal) and the \fIcode\fR element will be the exit |
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| 98 | code returned by the process (also in decimal). |
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| 99 | .TP |
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| 100 | \fBCHILDSUSP\fI pid sigName msg\fR |
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| 101 | This format is used when a child process has been suspended because |
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| 102 | of a signal. |
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| 103 | The \fIpid\fR element will be the process's identifier, in decimal. |
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| 104 | The \fIsigName\fR element will be the symbolic name of the signal that caused |
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| 105 | the process to suspend; this will be one of the names from the |
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| 106 | include file signal.h, such as \fBSIGTTIN\fR. |
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| 107 | The \fImsg\fR element will be a short human-readable message |
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| 108 | describing the signal, such as |
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| 109 | .QW "background tty read" |
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| 110 | for \fBSIGTTIN\fR. |
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| 111 | .TP |
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| 112 | \fBNONE\fR |
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| 113 | This format is used for errors where no additional information is |
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| 114 | available for an error besides the message returned with the |
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| 115 | error. In these cases the \fB\-errorcode\fR return option |
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| 116 | will consist of a list containing a single element whose |
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| 117 | contents are \fBNONE\fR. |
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| 118 | .TP |
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| 119 | \fBPOSIX \fIerrName msg\fR |
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| 120 | If the first element is \fBPOSIX\fR, then |
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| 121 | the error occurred during a POSIX kernel call. |
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| 122 | The \fIerrName\fR element will contain the symbolic name |
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| 123 | of the error that occurred, such as \fBENOENT\fR; this will |
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| 124 | be one of the values defined in the include file errno.h. |
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| 125 | The \fImsg\fR element will be a human-readable |
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| 126 | message corresponding to \fIerrName\fR, such as |
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| 127 | .QW "no such file or directory" |
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| 128 | for the \fBENOENT\fR case. |
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| 129 | .PP |
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| 130 | To set the \fB\-errorcode\fR return option, applications should use library |
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| 131 | procedures such as \fBTcl_SetObjErrorCode\fR, \fBTcl_SetReturnOptions\fR, |
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| 132 | and \fBTcl_PosixError\fR, or they may invoke the \fB\-errorcode\fR |
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| 133 | option of the \fBreturn\fR command. |
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| 134 | If none of these methods for setting the error code has been used, |
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| 135 | the Tcl interpreter will reset the variable to \fBNONE\fR after |
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| 136 | the next error. |
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| 137 | .RE |
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| 138 | .\" .TP |
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| 139 | .\" \fBTCL\fR ... |
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| 140 | .\" . |
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| 141 | .\" Indicates some sort of problem generated in relation to Tcl itself, |
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| 142 | .\" e.g. a failure to look up a channel or variable. |
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| 143 | .TP |
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| 144 | \fBerrorInfo\fR |
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| 145 | This variable holds the value of the \fB\-errorinfo\fR return option |
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| 146 | set by the most recent error that occurred in this interpreter. |
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| 147 | This string value will contain one or more lines |
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| 148 | identifying the Tcl commands and procedures that were being executed |
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| 149 | when the most recent error occurred. |
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| 150 | Its contents take the form of a stack trace showing the various |
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| 151 | nested Tcl commands that had been invoked at the time of the error. |
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| 152 | .TP |
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| 153 | \fBtcl_library\fR |
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| 154 | This variable holds the name of a directory containing the |
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| 155 | system library of Tcl scripts, such as those used for auto-loading. |
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| 156 | The value of this variable is returned by the \fBinfo library\fR command. |
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| 157 | See the \fBlibrary\fR manual entry for details of the facilities |
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| 158 | provided by the Tcl script library. |
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| 159 | Normally each application or package will have its own application-specific |
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| 160 | script library in addition to the Tcl script library; |
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| 161 | each application should set a global variable with a name like |
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| 162 | \fB$\fIapp\fB_library\fR (where \fIapp\fR is the application's name) |
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| 163 | to hold the network file name for that application's library directory. |
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| 164 | The initial value of \fBtcl_library\fR is set when an interpreter |
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| 165 | is created by searching several different directories until one is |
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| 166 | found that contains an appropriate Tcl startup script. |
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| 167 | If the \fBTCL_LIBRARY\fR environment variable exists, then |
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| 168 | the directory it names is checked first. |
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| 169 | If \fBTCL_LIBRARY\fR is not set or doesn't refer to an appropriate |
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| 170 | directory, then Tcl checks several other directories based on a |
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| 171 | compiled-in default location, the location of the binary containing |
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| 172 | the application, and the current working directory. |
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| 173 | .TP |
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| 174 | \fBtcl_patchLevel\fR |
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| 175 | . |
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| 176 | When an interpreter is created Tcl initializes this variable to |
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| 177 | hold a string giving the current patch level for Tcl, such as |
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| 178 | \fB8.4.16\fR for Tcl 8.4 with the first sixteen official patches, or |
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| 179 | \fB8.5b3\fR for the third beta release of Tcl 8.5. |
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| 180 | The value of this variable is returned by the \fBinfo patchlevel\fR |
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| 181 | command. |
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| 182 | .TP |
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| 183 | \fBtcl_pkgPath\fR |
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| 184 | This variable holds a list of directories indicating where packages are |
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| 185 | normally installed. It is not used on Windows. It typically contains |
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| 186 | either one or two entries; if it contains two entries, the first is |
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| 187 | normally a directory for platform-dependent packages (e.g., shared library |
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| 188 | binaries) and the second is normally a directory for platform-independent |
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| 189 | packages (e.g., script files). Typically a package is installed as a |
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| 190 | subdirectory of one of the entries in \fB$tcl_pkgPath\fR. The directories |
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| 191 | in \fB$tcl_pkgPath\fR are included by default in the \fBauto_path\fR |
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| 192 | variable, so they and their immediate subdirectories are automatically |
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| 193 | searched for packages during \fBpackage require\fR commands. Note: |
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| 194 | \fBtcl_pkgPath\fR is not intended to be modified by the application. Its |
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| 195 | value is added to \fBauto_path\fR at startup; changes to \fBtcl_pkgPath\fR |
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| 196 | are not reflected in \fBauto_path\fR. If you want Tcl to search additional |
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| 197 | directories for packages you should add the names of those directories to |
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| 198 | \fBauto_path\fR, not \fBtcl_pkgPath\fR. |
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| 199 | .TP |
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| 200 | \fBtcl_platform\fR |
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| 201 | This is an associative array whose elements contain information about |
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| 202 | the platform on which the application is running, such as the name of |
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| 203 | the operating system, its current release number, and the machine's |
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| 204 | instruction set. The elements listed below will always |
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| 205 | be defined, but they may have empty strings as values if Tcl could not |
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| 206 | retrieve any relevant information. In addition, extensions |
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| 207 | and applications may add additional values to the array. The |
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| 208 | predefined elements are: |
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| 209 | .RS |
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| 210 | .TP |
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| 211 | \fBbyteOrder\fR |
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| 212 | The native byte order of this machine: either \fBlittleEndian\fR or |
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| 213 | \fBbigEndian\fR. |
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| 214 | .TP |
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| 215 | \fBdebug\fR |
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| 216 | If this variable exists, then the interpreter was compiled with and linked |
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| 217 | to a debug-enabled C run-time. This variable will only exist on Windows, |
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| 218 | so extension writers can specify which package to load depending on the |
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| 219 | C run-time library that is in use. This is not an indication that this core |
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| 220 | contains symbols. |
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| 221 | .TP |
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| 222 | \fBmachine\fR |
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| 223 | The instruction set executed by this machine, such as |
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| 224 | \fBintel\fR, \fBPPC\fR, \fB68k\fR, or \fBsun4m\fR. On UNIX machines, this |
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| 225 | is the value returned by \fBuname -m\fR. |
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| 226 | .TP |
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| 227 | \fBos\fR |
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| 228 | The name of the operating system running on this machine, |
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| 229 | such as \fBWindows 95\fR, \fBWindows NT\fR, or \fBSunOS\fR. |
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| 230 | On UNIX machines, this is the value returned by \fBuname -s\fR. |
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| 231 | On Windows 95 and Windows 98, the value returned will be \fBWindows |
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| 232 | 95\fR to provide better backwards compatibility to Windows 95; to |
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| 233 | distinguish between the two, check the \fBosVersion\fR. |
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| 234 | .TP |
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| 235 | \fBosVersion\fR |
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| 236 | The version number for the operating system running on this machine. |
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| 237 | On UNIX machines, this is the value returned by \fBuname -r\fR. On |
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| 238 | Windows 95, the version will be 4.0; on Windows 98, the version will |
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| 239 | be 4.10. |
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| 240 | .TP |
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| 241 | \fBplatform\fR |
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| 242 | Either \fBwindows\fR, or \fBunix\fR. This identifies the |
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| 243 | general operating environment of the machine. |
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| 244 | .TP |
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| 245 | \fBthreaded\fR |
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| 246 | If this variable exists, then the interpreter |
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| 247 | was compiled with threads enabled. |
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| 248 | .TP |
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| 249 | \fBuser\fR |
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| 250 | This identifies the |
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| 251 | current user based on the login information available on the platform. |
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| 252 | This comes from the USER or LOGNAME environment variable on Unix, |
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| 253 | and the value from GetUserName on Windows. |
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| 254 | .TP |
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| 255 | \fBwordSize\fR |
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| 256 | This gives the size of the native-machine word in bytes (strictly, it |
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| 257 | is same as the result of evaluating \fIsizeof(long)\fR in C.) |
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| 258 | .TP |
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| 259 | \fBpointerSize\fR |
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| 260 | This gives the size of the native-machine pointer in bytes (strictly, it |
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| 261 | is same as the result of evaluating \fIsizeof(void*)\fR in C.) |
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| 262 | .RE |
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| 263 | .TP |
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| 264 | \fBtcl_precision\fR |
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| 265 | This variable controls the number of digits to generate |
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| 266 | when converting floating-point values to strings. It defaults |
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| 267 | .VS 8.5 |
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| 268 | to 0. \fIApplications should not change this value;\fR it is |
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| 269 | provided for compatibility with legacy code. |
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| 270 | .PP |
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| 271 | .RS |
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| 272 | The default value of 0 is special, meaning that Tcl should |
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| 273 | convert numbers using as few digits as possible while still |
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| 274 | distinguishing any floating point number from its nearest |
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| 275 | neighbours. It differs from using an arbitrarily high value |
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| 276 | for \fItcl_precision\fR in that an inexact number like \fI1.4\fR |
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| 277 | will convert as \fI1.4\fR rather than \fI1.3999999999999999\fR |
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| 278 | even though the latter is nearer to the exact value of the |
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| 279 | binary number. |
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| 280 | .RE |
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| 281 | .VE 8.5 |
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| 282 | .PP |
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| 283 | .RS |
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| 284 | 17 digits is |
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| 285 | .QW perfect |
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| 286 | for IEEE floating-point in that it allows |
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| 287 | double-precision values to be converted to strings and back to |
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| 288 | binary with no loss of information. However, using 17 digits prevents |
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| 289 | any rounding, which produces longer, less intuitive results. For example, |
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| 290 | \fBexpr {1.4}\fR returns 1.3999999999999999 with \fBtcl_precision\fR |
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| 291 | set to 17, vs. 1.4 if \fBtcl_precision\fR is 12. |
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| 292 | .RE |
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| 293 | .PP |
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| 294 | .RS |
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| 295 | All interpreters in a thread share a single \fBtcl_precision\fR value: |
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| 296 | changing it in one interpreter will affect all other interpreters as |
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| 297 | well. However, safe interpreters are not allowed to modify the |
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| 298 | variable. |
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| 299 | .RE |
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| 300 | .TP |
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| 301 | \fBtcl_rcFileName\fR |
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| 302 | This variable is used during initialization to indicate the name of a |
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| 303 | user-specific startup file. If it is set by application-specific |
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| 304 | initialization, then the Tcl startup code will check for the existence |
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| 305 | of this file and \fBsource\fR it if it exists. For example, for \fBwish\fR |
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| 306 | the variable is set to \fB~/.wishrc\fR for Unix and \fB~/wishrc.tcl\fR |
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| 307 | for Windows. |
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| 308 | .TP |
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| 309 | \fBtcl_traceCompile\fR |
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| 310 | The value of this variable can be set to control |
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| 311 | how much tracing information |
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| 312 | is displayed during bytecode compilation. |
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| 313 | By default, tcl_traceCompile is zero and no information is displayed. |
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| 314 | Setting tcl_traceCompile to 1 generates a one-line summary in stdout |
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| 315 | whenever a procedure or top-level command is compiled. |
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| 316 | Setting it to 2 generates a detailed listing in stdout of the |
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| 317 | bytecode instructions emitted during every compilation. |
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| 318 | This variable is useful in |
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| 319 | tracking down suspected problems with the Tcl compiler. |
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| 320 | .PP |
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| 321 | .RS |
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| 322 | This variable and functionality only exist if |
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| 323 | \fBTCL_COMPILE_DEBUG\fR was defined during Tcl's compilation. |
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| 324 | .RE |
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| 325 | .TP |
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| 326 | \fBtcl_traceExec\fR |
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| 327 | The value of this variable can be set to control |
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| 328 | how much tracing information |
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| 329 | is displayed during bytecode execution. |
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| 330 | By default, tcl_traceExec is zero and no information is displayed. |
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| 331 | Setting tcl_traceExec to 1 generates a one-line trace in stdout |
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| 332 | on each call to a Tcl procedure. |
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| 333 | Setting it to 2 generates a line of output |
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| 334 | whenever any Tcl command is invoked |
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| 335 | that contains the name of the command and its arguments. |
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| 336 | Setting it to 3 produces a detailed trace showing the result of |
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| 337 | executing each bytecode instruction. |
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| 338 | Note that when tcl_traceExec is 2 or 3, |
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| 339 | commands such as \fBset\fR and \fBincr\fR |
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| 340 | that have been entirely replaced by a sequence |
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| 341 | of bytecode instructions are not shown. |
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| 342 | Setting this variable is useful in |
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| 343 | tracking down suspected problems with the bytecode compiler |
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| 344 | and interpreter. |
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| 345 | .PP |
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| 346 | .RS |
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| 347 | This variable and functionality only exist if |
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| 348 | \fBTCL_COMPILE_DEBUG\fR was defined during Tcl's compilation. |
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| 349 | .RE |
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| 350 | .TP |
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| 351 | \fBtcl_wordchars\fR |
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| 352 | The value of this variable is a regular expression that can be set to |
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| 353 | control what are considered |
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| 354 | .QW word |
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| 355 | characters, for instances like |
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| 356 | selecting a word by double-clicking in text in Tk. It is platform |
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| 357 | dependent. On Windows, it defaults to \fB\eS\fR, meaning anything |
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| 358 | but a Unicode space character. Otherwise it defaults to \fB\ew\fR, |
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| 359 | which is any Unicode word character (number, letter, or underscore). |
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| 360 | .TP |
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| 361 | \fBtcl_nonwordchars\fR |
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| 362 | The value of this variable is a regular expression that can be set to |
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| 363 | control what are considered |
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| 364 | .QW non-word |
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| 365 | characters, for instances like |
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| 366 | selecting a word by double-clicking in text in Tk. It is platform |
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| 367 | dependent. On Windows, it defaults to \fB\es\fR, meaning any Unicode space |
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| 368 | character. Otherwise it defaults to \fB\eW\fR, which is anything but a |
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| 369 | Unicode word character (number, letter, or underscore). |
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| 370 | .TP |
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| 371 | \fBtcl_version\fR |
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| 372 | When an interpreter is created Tcl initializes this variable to |
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| 373 | hold the version number for this version of Tcl in the form \fIx.y\fR. |
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| 374 | Changes to \fIx\fR represent major changes with probable |
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| 375 | incompatibilities and changes to \fIy\fR represent small enhancements and |
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| 376 | bug fixes that retain backward compatibility. |
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| 377 | The value of this variable is returned by the \fBinfo tclversion\fR |
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| 378 | command. |
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| 379 | .SH "OTHER GLOBAL VARIABLES" |
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| 380 | The following variables are only guaranteed to exist in \fBtclsh\fR |
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| 381 | and \fBwish\fR executables; the Tcl library does not define them |
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| 382 | itself but many Tcl environments do. |
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| 383 | .TP 6 |
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| 384 | \fBargc\fR |
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| 385 | The number of arguments to \fBtclsh\fR or \fBwish\fR. |
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| 386 | .TP 6 |
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| 387 | \fBargv\fR |
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| 388 | Tcl list of arguments to \fBtclsh\fR or \fBwish\fR. |
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| 389 | .TP 6 |
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| 390 | \fBargv0\fR |
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| 391 | The script that \fBtclsh\fR or \fBwish\fR started executing (if it was |
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| 392 | specified) or otherwise the name by which \fBtclsh\fR or \fBwish\fR |
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| 393 | was invoked. |
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| 394 | .TP 6 |
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| 395 | \fBtcl_interactive\fR |
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| 396 | Contains 1 if \fBtclsh\fR or \fBwish\fR is running interactively (no |
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| 397 | script was specified and standard input is a terminal-like device), 0 |
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| 398 | otherwise. |
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| 399 | .PP |
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| 400 | The \fBwish\fR executable additionally specifies the following global |
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| 401 | variable: |
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| 402 | .TP 6 |
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| 403 | \fBgeometry\fR |
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| 404 | If set, contains the user-supplied geometry specification to use for |
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| 405 | the main Tk window. |
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| 406 | .SH "SEE ALSO" |
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| 407 | eval(n), tclsh(1), wish(1) |
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| 408 | .SH KEYWORDS |
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| 409 | arithmetic, bytecode, compiler, error, environment, POSIX, precision, subprocess, variables |
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