567 lines
21 KiB
Plaintext
567 lines
21 KiB
Plaintext
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'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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.TH tclvars n 8.0 Tcl "Tcl Built-In Commands"
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.so man.macros
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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argc, argv, argv0, auto_path, env, errorCode, errorInfo, tcl_interactive, tcl_library, tcl_nonwordchars, tcl_patchLevel, tcl_pkgPath, tcl_platform, tcl_precision, tcl_rcFileName, tcl_traceCompile, tcl_traceExec, tcl_wordchars, tcl_version \- Variables used by Tcl
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.BE
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.SH DESCRIPTION
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.PP
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The following global variables are created and managed automatically
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by the Tcl library. Except where noted below, these variables should
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normally be treated as read-only by application-specific code and by users.
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.TP
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\fBauto_path\fR
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.
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If set, then it must contain a valid Tcl list giving directories to
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search during auto-load operations (including for package index
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files when using the default \fBpackage unknown\fR handler).
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This variable is initialized during startup to contain, in order:
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the directories listed in the \fBTCLLIBPATH\fR environment variable,
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the directory named by the \fBtcl_library\fR global variable,
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the parent directory of \fBtcl_library\fR,
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the directories listed in the \fBtcl_pkgPath\fR variable.
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Additional locations to look for files and package indices should
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normally be added to this variable using \fBlappend\fR.
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.RS
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.PP
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Additional variables relating to package management exist. More
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details are listed in the \fBVARIABLES\fR section of the \fBlibrary\fR
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manual page.
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.RE
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.TP
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\fBenv\fR
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.
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This variable is maintained by Tcl as an array
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whose elements are the environment variables for the process.
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Reading an element will return the value of the corresponding
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environment variable.
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Setting an element of the array will modify the corresponding
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environment variable or create a new one if it does not already
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exist.
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Unsetting an element of \fBenv\fR will remove the corresponding
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environment variable.
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Changes to the \fBenv\fR array will affect the environment
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passed to children by commands like \fBexec\fR.
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If the entire \fBenv\fR array is unset then Tcl will stop
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monitoring \fBenv\fR accesses and will not update environment
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variables.
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.RS
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.PP
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Under Windows, the environment variables PATH and COMSPEC in any
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capitalization are converted automatically to upper case. For instance, the
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PATH variable could be exported by the operating system as
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.QW path ,
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.QW Path ,
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.QW PaTh ,
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etc., causing otherwise simple Tcl code to have to
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support many special cases. All other environment variables inherited by
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Tcl are left unmodified. Setting an env array variable to blank is the
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same as unsetting it as this is the behavior of the underlying Windows OS.
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It should be noted that relying on an existing and empty environment variable
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will not work on Windows and is discouraged for cross-platform usage.
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.PP
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The following elements of \fBenv\fR are special to Tcl:
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.TP
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\fBenv(HOME)\fR
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.
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This environment variable, if set, gives the location of the directory
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considered to be the current user's home directory, and to which a
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call of \fBcd\fR without arguments or with just
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.QW ~
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as an argument will change into. Most platforms set this correctly by
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default; it does not normally need to be set by user code.
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.TP
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\fBenv(TCL_LIBRARY)\fR
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.
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If set, then it specifies the location of the directory containing
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library scripts (the value of this variable will be
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assigned to the \fBtcl_library\fR variable and therefore returned by
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the command \fBinfo library\fR). If this variable is not set then
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a default value is used.
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.RS
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.PP
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Note that this environment variable should \fInot\fR normally be set.
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.RE
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.TP
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\fBenv(TCLLIBPATH)\fR
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.
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If set, then it must contain a valid Tcl list giving directories to
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search during auto-load operations. Directories must be specified in
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Tcl format, using
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.QW /
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as the path separator, regardless of platform.
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This variable is only used when initializing the \fBauto_path\fR variable.
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.TP
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\fBenv(TCL_TZ)\fR, \fBenv(TZ)\fR
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.
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These specify the default timezone used for parsing and formatting times and
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dates in the \fBclock\fR command. On many platforms, the TZ environment
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variable is set up by the operating system.
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.TP
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\fBenv(LC_ALL)\fR, \fBenv(LC_MESSAGES)\fR, \fBenv(LANG)\fR
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.
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These environment variables are used by the \fBmsgcat\fR package to
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determine what locale to format messages using.
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.TP
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\fBenv(TCL_INTERP_DEBUG_FRAME)\fR
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.
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If existing, it has the same effect as running \fBinterp debug\fR
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\fB{} -frame 1\fR
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as the very first command of each new Tcl interpreter.
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.RE
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.TP
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\fBerrorCode\fR
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.
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This variable holds the value of the \fB\-errorcode\fR return option
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set by the most recent error that occurred in this interpreter.
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This list value represents additional information about the error
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in a form that is easy to process with programs.
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The first element of the list identifies a general class of
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errors, and determines the format of the rest of the list.
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The following formats for \fB\-errorcode\fR return options
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are used by the Tcl core; individual applications may define
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additional formats.
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.RS
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.TP
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\fBARITH\fI code msg\fR
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.
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This format is used when an arithmetic error occurs (e.g. an attempt
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to divide zero by zero in the \fBexpr\fR command).
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\fICode\fR identifies the precise error and \fImsg\fR provides a
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human-readable description of the error. \fICode\fR will be either
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DIVZERO (for an attempt to divide by zero),
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DOMAIN (if an argument is outside the domain of a function, such as acos(\-3)),
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IOVERFLOW (for integer overflow),
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OVERFLOW (for a floating-point overflow),
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or UNKNOWN (if the cause of the error cannot be determined).
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.RS
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.PP
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Detection of these errors depends in part on the underlying hardware
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and system libraries.
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.RE
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.TP
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\fBCHILDKILLED\fI pid sigName msg\fR
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.
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This format is used when a child process has been killed because of
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a signal. The \fIpid\fR element will be the process's identifier (in decimal).
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The \fIsigName\fR element will be the symbolic name of the signal that caused
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the process to terminate; it will be one of the names from the
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include file signal.h, such as \fBSIGPIPE\fR.
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The \fImsg\fR element will be a short human-readable message
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describing the signal, such as
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.QW "write on pipe with no readers"
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for \fBSIGPIPE\fR.
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.TP
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\fBCHILDSTATUS\fI pid code\fR
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.
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This format is used when a child process has exited with a non-zero
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exit status. The \fIpid\fR element will be the
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process's identifier (in decimal) and the \fIcode\fR element will be the exit
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code returned by the process (also in decimal).
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.TP
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\fBCHILDSUSP\fI pid sigName msg\fR
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.
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This format is used when a child process has been suspended because
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of a signal.
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The \fIpid\fR element will be the process's identifier, in decimal.
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The \fIsigName\fR element will be the symbolic name of the signal that caused
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the process to suspend; this will be one of the names from the
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include file signal.h, such as \fBSIGTTIN\fR.
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The \fImsg\fR element will be a short human-readable message
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describing the signal, such as
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.QW "background tty read"
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for \fBSIGTTIN\fR.
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.TP
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\fBNONE\fR
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.
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This format is used for errors where no additional information is
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available for an error besides the message returned with the
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error. In these cases the \fB\-errorcode\fR return option
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will consist of a list containing a single element whose
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contents are \fBNONE\fR.
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.TP
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\fBPOSIX \fIerrName msg\fR
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.
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If the first element is \fBPOSIX\fR, then
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the error occurred during a POSIX kernel call.
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The \fIerrName\fR element will contain the symbolic name
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of the error that occurred, such as \fBENOENT\fR; this will
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be one of the values defined in the include file errno.h.
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The \fImsg\fR element will be a human-readable
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message corresponding to \fIerrName\fR, such as
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.QW "no such file or directory"
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for the \fBENOENT\fR case.
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.TP
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\fBTCL\fR ...
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.
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Indicates some sort of problem generated in relation to Tcl itself, e.g. a
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failure to look up a channel or variable.
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.PP
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To set the \fB\-errorcode\fR return option, applications should use library
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procedures such as \fBTcl_SetObjErrorCode\fR, \fBTcl_SetReturnOptions\fR,
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and \fBTcl_PosixError\fR, or they may invoke the \fB\-errorcode\fR
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option of the \fBreturn\fR command.
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If none of these methods for setting the error code has been used,
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the Tcl interpreter will reset the variable to \fBNONE\fR after
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the next error.
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.RE
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.TP
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\fBerrorInfo\fR
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.
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This variable holds the value of the \fB\-errorinfo\fR return option
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set by the most recent error that occurred in this interpreter.
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This string value will contain one or more lines
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identifying the Tcl commands and procedures that were being executed
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when the most recent error occurred.
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Its contents take the form of a stack trace showing the various
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nested Tcl commands that had been invoked at the time of the error.
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.TP
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\fBtcl_library\fR
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.
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This variable holds the name of a directory containing the
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system library of Tcl scripts, such as those used for auto-loading.
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The value of this variable is returned by the \fBinfo library\fR command.
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See the \fBlibrary\fR manual entry for details of the facilities
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provided by the Tcl script library.
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Normally each application or package will have its own application-specific
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script library in addition to the Tcl script library;
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each application should set a global variable with a name like
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\fB$\fIapp\fB_library\fR (where \fIapp\fR is the application's name)
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to hold the network file name for that application's library directory.
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The initial value of \fBtcl_library\fR is set when an interpreter
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is created by searching several different directories until one is
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found that contains an appropriate Tcl startup script.
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If the \fBTCL_LIBRARY\fR environment variable exists, then
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the directory it names is checked first.
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If \fBTCL_LIBRARY\fR is not set or doesn't refer to an appropriate
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directory, then Tcl checks several other directories based on a
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compiled-in default location, the location of the binary containing
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the application, and the current working directory.
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.TP
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\fBtcl_patchLevel\fR
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.
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When an interpreter is created Tcl initializes this variable to
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hold a string giving the current patch level for Tcl, such as
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\fB8.4.16\fR for Tcl 8.4 with the first sixteen official patches, or
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\fB8.5b3\fR for the third beta release of Tcl 8.5.
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The value of this variable is returned by the \fBinfo patchlevel\fR
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command.
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.TP
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\fBtcl_pkgPath\fR
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.
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This variable holds a list of directories indicating where packages are
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normally installed. It is not used on Windows. It typically contains
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either one or two entries; if it contains two entries, the first is
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normally a directory for platform-dependent packages (e.g., shared library
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binaries) and the second is normally a directory for platform-independent
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packages (e.g., script files). Typically a package is installed as a
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subdirectory of one of the entries in the \fBtcl_pkgPath\fR
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variable. The directories in the \fBtcl_pkgPath\fR variable are
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included by default in the \fBauto_path\fR
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variable, so they and their immediate subdirectories are automatically
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searched for packages during \fBpackage require\fR commands. Note:
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\fBtcl_pkgPath\fR is not intended to be modified by the application. Its
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value is added to \fBauto_path\fR at startup; changes to \fBtcl_pkgPath\fR
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are not reflected in \fBauto_path\fR. If you want Tcl to search additional
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directories for packages you should add the names of those directories to
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\fBauto_path\fR, not \fBtcl_pkgPath\fR.
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.TP
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\fBtcl_platform\fR
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.
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This is an associative array whose elements contain information about
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the platform on which the application is running, such as the name of
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the operating system, its current release number, and the machine's
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instruction set. The elements listed below will always
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be defined, but they may have empty strings as values if Tcl could not
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retrieve any relevant information. In addition, extensions
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and applications may add additional values to the array. The
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predefined elements are:
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.RS
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.TP
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\fBbyteOrder\fR
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.
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The native byte order of this machine: either \fBlittleEndian\fR or
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\fBbigEndian\fR.
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.TP
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\fBdebug\fR
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.
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If this variable exists, then the interpreter was compiled with and linked
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to a debug-enabled C run-time. This variable will only exist on Windows,
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so extension writers can specify which package to load depending on the
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C run-time library that is in use. This is not an indication that this core
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contains symbols.
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.TP
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\fBengine\fR
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.
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The name of the Tcl language implementation. When the interpreter is first
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created, this is always set to the string \fBTcl\fR.
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.TP
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\fBmachine\fR
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.
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The instruction set executed by this machine, such as
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\fBintel\fR, \fBPPC\fR, \fB68k\fR, or \fBsun4m\fR. On UNIX machines, this
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is the value returned by \fBuname -m\fR.
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.TP
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\fBos\fR
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.
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The name of the operating system running on this machine,
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such as \fBWindows NT\fR or \fBSunOS\fR.
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On UNIX machines, this is the value returned by \fBuname -s\fR.
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.TP
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\fBosVersion\fR
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.
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The version number for the operating system running on this machine.
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On UNIX machines, this is the value returned by \fBuname -r\fR.
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.TP
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\fBpathSeparator\fR
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|
.VS 8.6
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|
'\" Defined by TIP #315
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The character that should be used to \fBsplit\fR PATH-like environment
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variables into their corresponding list of directory names.
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.VE 8.6
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.TP
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\fBplatform\fR
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.
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Either \fBwindows\fR, or \fBunix\fR. This identifies the
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general operating environment of the machine.
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.TP
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\fBpointerSize\fR
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.
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This gives the size of the native-machine pointer in bytes (strictly, it
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is same as the result of evaluating \fIsizeof(void*)\fR in C.)
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.TP
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\fBthreaded\fR
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.
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If this variable exists, then the interpreter
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was compiled with threads enabled.
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|
.TP
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\fBuser\fR
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.
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This identifies the
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current user based on the login information available on the platform.
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|
This value comes from the getuid() and getpwuid() system calls on Unix,
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and the value from the GetUserName() system call on Windows.
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.TP
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|
\fBwordSize\fR
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.
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|
This gives the size of the native-machine word in bytes (strictly, it
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is same as the result of evaluating \fIsizeof(long)\fR in C.)
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.RE
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.TP
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\fBtcl_precision\fR
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|
.
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|
This variable controls the number of digits to generate
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when converting floating-point values to strings. It defaults
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to 0. \fIApplications should not change this value;\fR it is
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provided for compatibility with legacy code.
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.PP
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.RS
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The default value of 0 is special, meaning that Tcl should
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convert numbers using as few digits as possible while still
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distinguishing any floating point number from its nearest
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neighbours. It differs from using an arbitrarily high value
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for \fItcl_precision\fR in that an inexact number like \fI1.4\fR
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will convert as \fI1.4\fR rather than \fI1.3999999999999999\fR
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even though the latter is nearer to the exact value of the
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binary number.
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.RE
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.PP
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|
.RS
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If \fBtcl_precision\fR is not zero, then when Tcl converts a floating
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point number, it creates a decimal representation of at most
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\fBtcl_precision\fR significant digits; the result may be shorter if
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the shorter result represents the original number exactly. If no
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result of at most \fBtcl_precision\fR digits is an exact representation
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of the original number, the one that is closest to the original
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number is chosen.
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If the original number lies precisely between two equally accurate
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||
|
decimal representations, then the one with an even value for the least
|
||
|
significant digit is chosen; for instance, if \fBtcl_precision\fR is 3, then
|
||
|
0.3125 will convert to 0.312, not 0.313, while 0.6875 will convert to
|
||
|
0.688, not 0.687. Any string of trailing zeroes that remains is trimmed.
|
||
|
.RE
|
||
|
.PP
|
||
|
.RS
|
||
|
a \fBtcl_precision\fR value of 17 digits is
|
||
|
.QW 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. For this reason, you will often
|
||
|
see it as a value in legacy code that must run on Tcl versions before
|
||
|
8.5. It is no longer recommended; as noted above, a zero value is the
|
||
|
preferred method.
|
||
|
.RE
|
||
|
.PP
|
||
|
.RS
|
||
|
All interpreters in a thread share a single \fBtcl_precision\fR value:
|
||
|
changing it in one interpreter will affect all other interpreters as
|
||
|
well. Safe interpreters are not allowed to modify the
|
||
|
variable.
|
||
|
.RE
|
||
|
.PP
|
||
|
.RS
|
||
|
Valid values for \fBtcl_precision\fR range from 0 to 17.
|
||
|
.RE
|
||
|
.TP
|
||
|
\fBtcl_rcFileName\fR
|
||
|
.
|
||
|
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 \fBsource\fR it if it exists. For example, for \fBwish\fR
|
||
|
the variable is set to \fB~/.wishrc\fR for Unix and \fB~/wishrc.tcl\fR
|
||
|
for Windows.
|
||
|
.TP
|
||
|
\fBtcl_traceCompile\fR
|
||
|
.
|
||
|
The value of this variable can be set to control
|
||
|
how much tracing information
|
||
|
is displayed during bytecode compilation.
|
||
|
By default, \fBtcl_traceCompile\fR is zero and no information is displayed.
|
||
|
Setting \fBtcl_traceCompile\fR to 1 generates a one-line summary in \fBstdout\fR
|
||
|
whenever a procedure or top-level command is compiled.
|
||
|
Setting it to 2 generates a detailed listing in \fBstdout\fR of the
|
||
|
bytecode instructions emitted during every compilation.
|
||
|
This variable is useful in
|
||
|
tracking down suspected problems with the Tcl compiler.
|
||
|
.PP
|
||
|
.RS
|
||
|
This variable and functionality only exist if
|
||
|
\fBTCL_COMPILE_DEBUG\fR was defined during Tcl's compilation.
|
||
|
.RE
|
||
|
.TP
|
||
|
\fBtcl_traceExec\fR
|
||
|
.
|
||
|
The value of this variable can be set to control
|
||
|
how much tracing information
|
||
|
is displayed during bytecode execution.
|
||
|
By default, \fBtcl_traceExec\fR is zero and no information is displayed.
|
||
|
Setting \fBtcl_traceExec\fR to 1 generates a one-line trace in \fBstdout\fR
|
||
|
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 produces a detailed trace showing the result of
|
||
|
executing each bytecode instruction.
|
||
|
Note that when \fBtcl_traceExec\fR is 2 or 3,
|
||
|
commands such as \fBset\fR and \fBincr\fR
|
||
|
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.
|
||
|
.PP
|
||
|
.RS
|
||
|
This variable and functionality only exist if
|
||
|
\fBTCL_COMPILE_DEBUG\fR was defined during Tcl's compilation.
|
||
|
.RE
|
||
|
.TP
|
||
|
\fBtcl_wordchars\fR
|
||
|
.
|
||
|
The value of this variable is a regular expression that can be set to
|
||
|
control what are considered
|
||
|
.QW word
|
||
|
characters, for instances like
|
||
|
selecting a word by double-clicking in text in Tk. It is platform
|
||
|
dependent. On Windows, it defaults to \fB\eS\fR, meaning anything
|
||
|
but a Unicode space character. Otherwise it defaults to \fB\ew\fR,
|
||
|
which is any Unicode word character (number, letter, or underscore).
|
||
|
.TP
|
||
|
\fBtcl_nonwordchars\fR
|
||
|
.
|
||
|
The value of this variable is a regular expression that can be set to
|
||
|
control what are considered
|
||
|
.QW 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 \fB\es\fR, meaning any Unicode space
|
||
|
character. Otherwise it defaults to \fB\eW\fR, which is anything but a
|
||
|
Unicode word character (number, letter, or underscore).
|
||
|
.TP
|
||
|
\fBtcl_version\fR
|
||
|
.
|
||
|
When an interpreter is created Tcl initializes this variable to
|
||
|
hold the version number for this version of Tcl in the form \fIx.y\fR.
|
||
|
Changes to \fIx\fR represent major changes with probable
|
||
|
incompatibilities and changes to \fIy\fR represent small enhancements and
|
||
|
bug fixes that retain backward compatibility.
|
||
|
The value of this variable is returned by the \fBinfo tclversion\fR
|
||
|
command.
|
||
|
.SH "OTHER GLOBAL VARIABLES"
|
||
|
.PP
|
||
|
The following variables are only guaranteed to exist in \fBtclsh\fR
|
||
|
and \fBwish\fR executables; the Tcl library does not define them
|
||
|
itself but many Tcl environments do.
|
||
|
.TP 6
|
||
|
\fBargc\fR
|
||
|
.
|
||
|
The number of arguments to \fBtclsh\fR or \fBwish\fR.
|
||
|
.TP 6
|
||
|
\fBargv\fR
|
||
|
.
|
||
|
Tcl list of arguments to \fBtclsh\fR or \fBwish\fR.
|
||
|
.TP 6
|
||
|
\fBargv0\fR
|
||
|
.
|
||
|
The script that \fBtclsh\fR or \fBwish\fR started executing (if it was
|
||
|
specified) or otherwise the name by which \fBtclsh\fR or \fBwish\fR
|
||
|
was invoked.
|
||
|
.TP 6
|
||
|
\fBtcl_interactive\fR
|
||
|
.
|
||
|
Contains 1 if \fBtclsh\fR or \fBwish\fR is running interactively (no
|
||
|
script was specified and standard input is a terminal-like device), 0
|
||
|
otherwise.
|
||
|
.SH EXAMPLES
|
||
|
.PP
|
||
|
To add a directory to the collection of locations searched by
|
||
|
\fBpackage require\fR, e.g., because of some application-specific
|
||
|
packages that are used, the \fBauto_path\fR variable needs to be
|
||
|
updated:
|
||
|
.PP
|
||
|
.CS
|
||
|
lappend ::\fBauto_path\fR [file join [pwd] "theLibDir"]
|
||
|
.CE
|
||
|
.PP
|
||
|
A simple though not very robust way to handle command line arguments
|
||
|
of the form
|
||
|
.QW "\-foo 1 \-bar 2"
|
||
|
is to load them into an array having first loaded in the default settings:
|
||
|
.CS
|
||
|
array set arguments {-foo 0 -bar 0 -grill 0}
|
||
|
array set arguments $::\fBargv\fR
|
||
|
puts "foo is $arguments(-foo)"
|
||
|
puts "bar is $arguments(-bar)"
|
||
|
puts "grill is $arguments(-grill)"
|
||
|
.CE
|
||
|
.PP
|
||
|
The \fBargv0\fR global variable can be used (in conjunction with the
|
||
|
\fBinfo script\fR command) to determine whether the current script is
|
||
|
being executed as the main script or loaded as a library. This is
|
||
|
useful because it allows a single script to be used as both a library
|
||
|
and a demonstration of that library:
|
||
|
.PP
|
||
|
.CS
|
||
|
if {$::\fBargv0\fR eq [info script]} {
|
||
|
# running as: tclsh example.tcl
|
||
|
} else {
|
||
|
package provide Example 1.0
|
||
|
}
|
||
|
.CE
|
||
|
.SH "SEE ALSO"
|
||
|
eval(n), library(n), tclsh(1), tkvars(n), wish(1)
|
||
|
.SH KEYWORDS
|
||
|
arithmetic, bytecode, compiler, error, environment, POSIX, precision,
|
||
|
subprocess, user, variables
|
||
|
'\" Local Variables:
|
||
|
'\" mode: nroff
|
||
|
'\" End:
|