405 lines
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405 lines
21 KiB
HTML
<HTML><HEAD><TITLE>Tcl Built-In Commands - tclvars manual page</TITLE></HEAD><BODY>
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<DL>
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<DD><A HREF="tclvars.htm#M2" NAME="L1260">NAME</A>
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<DL><DD>tclvars - Variables used by Tcl</DL>
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<DD><A HREF="tclvars.htm#M3" NAME="L1261">DESCRIPTION</A>
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<DL>
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<DD><A HREF="tclvars.htm#M4" NAME="L1262"><B>env</B></A>
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<DL>
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<DD><A HREF="tclvars.htm#M5" NAME="L1263"><B>LOGIN</B></A>
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<DD><A HREF="tclvars.htm#M6" NAME="L1264"><B>USER</B></A>
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<DD><A HREF="tclvars.htm#M7" NAME="L1265"><B>SYS_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M8" NAME="L1266"><B>APPLE_M_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M9" NAME="L1267"><B>CP_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M10" NAME="L1268"><B>DESK_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M11" NAME="L1269"><B>EXT_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M12" NAME="L1270"><B>PREF_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M13" NAME="L1271"><B>PRINT_MON_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M14" NAME="L1272"><B>SHARED_TRASH_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M15" NAME="L1273"><B>TRASH_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M16" NAME="L1274"><B>START_UP_FOLDER</B></A>
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<DD><A HREF="tclvars.htm#M17" NAME="L1275"><B>HOME</B></A>
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</DL>
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<DD><A HREF="tclvars.htm#M18" NAME="L1276"><B>errorCode</B></A>
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<DL>
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<DD><A HREF="tclvars.htm#M19" NAME="L1277"><B>ARITH</B><I> code msg</I></A>
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<DD><A HREF="tclvars.htm#M20" NAME="L1278"><B>CHILDKILLED</B><I> pid sigName msg</I></A>
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<DD><A HREF="tclvars.htm#M21" NAME="L1279"><B>CHILDSTATUS</B><I> pid code</I></A>
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<DD><A HREF="tclvars.htm#M22" NAME="L1280"><B>CHILDSUSP</B><I> pid sigName msg</I></A>
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<DD><A HREF="tclvars.htm#M23" NAME="L1281"><B>NONE</B></A>
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<DD><A HREF="tclvars.htm#M24" NAME="L1282"><B>POSIX </B><I>errName msg</I></A>
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</DL>
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<DD><A HREF="tclvars.htm#M25" NAME="L1283"><B>errorInfo</B></A>
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<DD><A HREF="tclvars.htm#M26" NAME="L1284"><B>tcl_library</B></A>
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<DD><A HREF="tclvars.htm#M27" NAME="L1285"><B>tcl_patchLevel</B></A>
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<DD><A HREF="tclvars.htm#M28" NAME="L1286"><B>tcl_pkgPath</B></A>
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<DD><A HREF="tclvars.htm#M29" NAME="L1287"><B>tcl_platform</B></A>
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<DL>
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<DD><A HREF="tclvars.htm#M30" NAME="L1288"><B>byteOrder</B></A>
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<DD><A HREF="tclvars.htm#M31" NAME="L1289"><B>debug</B></A>
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<DD><A HREF="tclvars.htm#M32" NAME="L1290"><B>machine</B></A>
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<DD><A HREF="tclvars.htm#M33" NAME="L1291"><B>os</B></A>
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<DD><A HREF="tclvars.htm#M34" NAME="L1292"><B>osVersion</B></A>
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<DD><A HREF="tclvars.htm#M35" NAME="L1293"><B>platform</B></A>
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<DD><A HREF="tclvars.htm#M36" NAME="L1294"><B>threaded</B></A>
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<DD><A HREF="tclvars.htm#M37" NAME="L1295"><B>user</B></A>
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</DL>
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<DD><A HREF="tclvars.htm#M38" NAME="L1296"><B>tcl_precision</B></A>
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<DD><A HREF="tclvars.htm#M39" NAME="L1297"><B>tcl_rcFileName</B></A>
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<DD><A HREF="tclvars.htm#M40" NAME="L1298"><B>tcl_rcRsrcName</B></A>
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<DD><A HREF="tclvars.htm#M41" NAME="L1299"><B>tcl_traceCompile</B></A>
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<DD><A HREF="tclvars.htm#M42" NAME="L1300"><B>tcl_traceExec</B></A>
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<DD><A HREF="tclvars.htm#M43" NAME="L1301"><B>tcl_wordchars</B></A>
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<DD><A HREF="tclvars.htm#M44" NAME="L1302"><B>tcl_nonwordchars</B></A>
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<DD><A HREF="tclvars.htm#M45" NAME="L1303"><B>tcl_version</B></A>
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</DL>
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<DD><A HREF="tclvars.htm#M46" NAME="L1304">SEE ALSO</A>
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<DD><A HREF="tclvars.htm#M47" NAME="L1305">KEYWORDS</A>
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</DL><HR>
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<H3><A NAME="M2">NAME</A></H3>
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tclvars - Variables used by Tcl
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<H3><A NAME="M3">DESCRIPTION</A></H3>
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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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<P>
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<DL>
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<P><DT><A NAME="M4"><B>env</B></A><DD>
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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 doesn't already
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exist.
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Unsetting an element of <B>env</B> will remove the corresponding
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environment variable.
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Changes to the <B>env</B> array will affect the environment
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passed to children by commands like <B><A HREF="../TkCmd/exec.htm">exec</A></B>.
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If the entire <B>env</B> array is unset then Tcl will stop
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monitoring <B>env</B> accesses and will not update environment
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variables.
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<DL><P><DD>
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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 ``path'',
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``Path'', ``PaTh'', 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.
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</DL>
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<DL><P><DD>
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On the Macintosh, the environment variable is constructed by Tcl as no
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global environment variable exists. The environment variables that
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are created for Tcl include:
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<P>
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<DL>
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<P><DT><A NAME="M5"><B>LOGIN</B></A><DD>
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This holds the Chooser name of the Macintosh.
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<P><DT><A NAME="M6"><B>USER</B></A><DD>
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This also holds the Chooser name of the Macintosh.
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<P><DT><A NAME="M7"><B>SYS_FOLDER</B></A><DD>
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The path to the system directory.
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<P><DT><A NAME="M8"><B>APPLE_M_FOLDER</B></A><DD>
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The path to the Apple Menu directory.
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<P><DT><A NAME="M9"><B>CP_FOLDER</B></A><DD>
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The path to the control panels directory.
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<P><DT><A NAME="M10"><B>DESK_FOLDER</B></A><DD>
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The path to the desk top directory.
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<P><DT><A NAME="M11"><B>EXT_FOLDER</B></A><DD>
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The path to the system extensions directory.
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<P><DT><A NAME="M12"><B>PREF_FOLDER</B></A><DD>
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The path to the preferences directory.
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<P><DT><A NAME="M13"><B>PRINT_MON_FOLDER</B></A><DD>
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The path to the print monitor directory.
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<P><DT><A NAME="M14"><B>SHARED_TRASH_FOLDER</B></A><DD>
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The path to the network trash directory.
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<P><DT><A NAME="M15"><B>TRASH_FOLDER</B></A><DD>
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The path to the trash directory.
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<P><DT><A NAME="M16"><B>START_UP_FOLDER</B></A><DD>
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The path to the start up directory.
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<P><DT><A NAME="M17"><B>HOME</B></A><DD>
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The path to the application's default directory.
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<P></DL>
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<P>
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You can also create your own environment variables for the Macintosh.
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A file named <I>Tcl Environment Variables</I> may be placed in the
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preferences folder in the Mac system folder. Each line of this file
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should be of the form <I>VAR_NAME=var_data</I>.
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<P>
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The last alternative is to place environment variables in a 'STR#'
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resource named <I>Tcl Environment Variables</I> of the application. This
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is considered a little more ``Mac like'' than a Unix style Environment
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Variable file. Each entry in the 'STR#' resource has the same format
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as above. The source code file <I>tclMacEnv.c</I> contains the
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implementation of the env mechanisms. This file contains many
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#define's that allow customization of the env mechanisms to fit your
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applications needs.
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</DL>
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<P><DT><A NAME="M18"><B>errorCode</B></A><DD>
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After an error has occurred, this variable will be set to hold
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additional information about the error in a form that is easy
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to process with programs.
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<B>errorCode</B> consists of a Tcl list with one or more elements.
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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 <B>errorCode</B> are used by the
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Tcl core; individual applications may define additional formats.
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<P>
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<DL>
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<P><DT><A NAME="M19"><B>ARITH</B><I> code msg</I></A><DD>
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This format is used when an arithmetic error occurs (e.g. an attempt
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to divide by zero in the <B><A HREF="../TkCmd/expr.htm">expr</A></B> command).
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<I>Code</I> identifies the precise error and <I>msg</I> provides a
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human-readable description of the error. <I>Code</I> 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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<P><DT><A NAME="M20"><B>CHILDKILLED</B><I> pid sigName msg</I></A><DD>
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This format is used when a child process has been killed because of
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a signal. The second element of <B>errorCode</B> will be the
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process's identifier (in decimal).
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The third 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 <B>SIGPIPE</B>.
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The fourth element will be a short human-readable message
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describing the signal, such as ``write on pipe with no readers''
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for <B>SIGPIPE</B>.
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<P><DT><A NAME="M21"><B>CHILDSTATUS</B><I> pid code</I></A><DD>
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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 second element of <B>errorCode</B> will be the
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process's identifier (in decimal) and the third element will be the exit
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code returned by the process (also in decimal).
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<P><DT><A NAME="M22"><B>CHILDSUSP</B><I> pid sigName msg</I></A><DD>
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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 second element of <B>errorCode</B> will be the process's identifier,
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in decimal.
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The third 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 <B>SIGTTIN</B>.
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The fourth element will be a short human-readable message
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describing the signal, such as ``background tty read''
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for <B>SIGTTIN</B>.
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<P><DT><A NAME="M23"><B>NONE</B></A><DD>
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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 <B>errorCode</B> will consist of a list
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containing a single element whose contents are <B>NONE</B>.
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<P><DT><A NAME="M24"><B>POSIX </B><I>errName msg</I></A><DD>
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If the first element of <B>errorCode</B> is <B>POSIX</B>, then
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the error occurred during a POSIX kernel call.
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The second element of the list will contain the symbolic name
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of the error that occurred, such as <B>ENOENT</B>; this will
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be one of the values defined in the include file errno.h.
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The third element of the list will be a human-readable
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message corresponding to <I>errName</I>, such as
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``no such file or directory'' for the <B>ENOENT</B> case.
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</DL><P>To set <B>errorCode</B>, applications should use library
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procedures such as <B><A HREF="../TkLib/AddErrInfo.htm">Tcl_SetErrorCode</A></B> and <B><A HREF="../TkLib/AddErrInfo.htm">Tcl_PosixError</A></B>,
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or they may invoke the <B><A HREF="../TkCmd/error.htm">error</A></B> command.
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If one of these methods hasn't been used, then the Tcl
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interpreter will reset the variable to <B>NONE</B> after
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the next error.<DL>
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<P></DL>
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<P><DT><A NAME="M25"><B>errorInfo</B></A><DD>
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After an error has occurred, this string 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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<P><DT><A NAME="M26"><B>tcl_library</B></A><DD>
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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 <B><A HREF="../TkCmd/info.htm">info library</A></B> command.
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See the <B>library</B> 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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<B>$</B><I>app</I><B>_library</B> (where <I>app</I> 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 <B>tcl_library</B> 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 <B>TCL_LIBRARY</B> environment variable exists, then
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the directory it names is checked first.
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If <B>TCL_LIBRARY</B> isn't 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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<P><DT><A NAME="M27"><B>tcl_patchLevel</B></A><DD>
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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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<B>7.3p2</B> for Tcl 7.3 with the first two official patches, or
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<B>7.4b4</B> for the fourth beta release of Tcl 7.4.
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The value of this variable is returned by the <B><A HREF="../TkCmd/info.htm">info patchlevel</A></B>
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command.
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<P><DT><A NAME="M28"><B>tcl_pkgPath</B></A><DD>
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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 <B>$tcl_pkgPath</B>. The directories
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in <B>$tcl_pkgPath</B> are included by default in the <B>auto_path</B>
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variable, so they and their immediate subdirectories are automatically
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searched for packages during <B>package require</B> commands. Note:
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<B>tcl_pkgPath</B> it not intended to be modified by the application. Its
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value is added to <B>auto_path</B> at startup; changes to <B>tcl_pkgPath</B>
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are not reflected in <B>auto_path</B>. 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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<B>auto_path</B>, not <B>tcl_pkgPath</B>.
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<P><DT><A NAME="M29"><B>tcl_platform</B></A><DD>
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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 couldn't
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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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<P>
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<DL>
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<P><DT><A NAME="M30"><B>byteOrder</B></A><DD>
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The native byte order of this machine: either <B>littleEndian</B> or
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<B>bigEndian</B>.
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<P><DT><A NAME="M31"><B>debug</B></A><DD>
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If this variable exists, then the interpreter
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was compiled with debugging symbols enabled. This varible will only
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exist on Windows so extension writers can specify which package to load
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depending on the C run-time library that is loaded.
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<P><DT><A NAME="M32"><B>machine</B></A><DD>
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The instruction set executed by this machine, such as
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<B>intel</B>, <B>PPC</B>, <B>68k</B>, or <B>sun4m</B>. On UNIX machines, this
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is the value returned by <B>uname -m</B>.
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<P><DT><A NAME="M33"><B>os</B></A><DD>
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The name of the operating system running on this machine,
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such as <B>Windows 95</B>, <B>Windows NT</B>, <B>MacOS</B>, or <B>SunOS</B>.
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On UNIX machines, this is the value returned by <B>uname -s</B>.
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On Windows 95 and Windows 98, the value returned will be <B>Windows
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95</B> to provide better backwards compatibility to Windows 95; to
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distinguish between the two, check the <B>osVersion</B>.
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<P><DT><A NAME="M34"><B>osVersion</B></A><DD>
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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 <B>uname -r</B>. On
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Windows 95, the version will be 4.0; on Windows 98, the version will
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be 4.10.
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<P><DT><A NAME="M35"><B>platform</B></A><DD>
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Either <B>windows</B>, <B>macintosh</B>, or <B>unix</B>. This identifies the
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general operating environment of the machine.
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<P><DT><A NAME="M36"><B>threaded</B></A><DD>
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If this variable exists, then the interpreter
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was compiled with threads enabled.
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<P><DT><A NAME="M37"><B>user</B></A><DD>
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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 comes from the USER or LOGNAME environment variable on Unix,
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and the value from GetUserName on Windows and Macintosh.
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<P></DL>
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<P><DT><A NAME="M38"><B>tcl_precision</B></A><DD>
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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 12.
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17 digits is ``perfect'' for IEEE floating-point in that it allows
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double-precision values to be converted to strings and back to
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binary with no loss of information. However, using 17 digits prevents
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any rounding, which produces longer, less intuitive results. For example,
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<B>expr 1.4</B> returns 1.3999999999999999 with <B>tcl_precision</B>
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set to 17, vs. 1.4 if <B>tcl_precision</B> is 12.
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<DL><P><DD>
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All interpreters in a process share a single <B>tcl_precision</B> value:
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changing it in one interpreter will affect all other interpreters as
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well. However, safe interpreters are not allowed to modify the
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variable.
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</DL>
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<P><DT><A NAME="M39"><B>tcl_rcFileName</B></A><DD>
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This variable is used during initialization to indicate the name of a
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user-specific startup file. If it is set by application-specific
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initialization, then the Tcl startup code will check for the existence
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of this file and <B><A HREF="../TkCmd/source.htm">source</A></B> it if it exists. For example, for <B><A HREF="../UserCmd/wish.htm">wish</A></B>
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the variable is set to <B>~/.wishrc</B> for Unix and <B>~/wishrc.tcl</B>
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for Windows.
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<P><DT><A NAME="M40"><B>tcl_rcRsrcName</B></A><DD>
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This variable is only used on Macintosh systems. The variable is used
|
|
during initialization to indicate the name of a user-specific
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|
<B><A HREF="../TclCmd/text.htm">TEXT</A></B> resource located in the application or extension resource
|
|
forks. If it is set by application-specific initialization, then the
|
|
Tcl startup code will check for the existence of this resource and
|
|
<B><A HREF="../TkCmd/source.htm">source</A></B> it if it exists. For example, the Macintosh <B><A HREF="../UserCmd/wish.htm">wish</A></B>
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application has the variable is set to <B>tclshrc</B>.
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|
<P><DT><A NAME="M41"><B>tcl_traceCompile</B></A><DD>
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The value of this variable can be set to control
|
|
how much tracing information
|
|
is displayed during bytecode compilation.
|
|
By default, tcl_traceCompile is zero and no information is displayed.
|
|
Setting tcl_traceCompile to 1 generates a one line summary in stdout
|
|
whenever a procedure or top level command is compiled.
|
|
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 converting
|
|
existing code to use Tcl8.0.
|
|
<P><DT><A NAME="M42"><B>tcl_traceExec</B></A><DD>
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|
The value of this variable can be set to control
|
|
how much tracing information
|
|
is displayed during bytecode execution.
|
|
By default, tcl_traceExec is zero and no information is displayed.
|
|
Setting tcl_traceExec 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 produces a detailed trace showing the result of
|
|
executing each bytecode instruction.
|
|
Note that when tcl_traceExec 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.
|
|
<P><DT><A NAME="M43"><B>tcl_wordchars</B></A><DD>
|
|
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 <B>\S</B>, meaning anything
|
|
but a Unicode space character. Otherwise it defaults to <B>\w</B>,
|
|
which is any Unicode word character (number, letter, or underscore).
|
|
<P><DT><A NAME="M44"><B>tcl_nonwordchars</B></A><DD>
|
|
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 <B>\s</B>, meaning any Unicode space
|
|
character. Otherwise it defaults to <B>\W</B>, which is anything but a
|
|
Unicode word character (number, letter, or underscore).
|
|
<P><DT><A NAME="M45"><B>tcl_version</B></A><DD>
|
|
When an interpreter is created Tcl initializes this variable to
|
|
hold the version number for this version of Tcl in the form <I>x.y</I>.
|
|
Changes to <I>x</I> represent major changes with probable
|
|
incompatibilities and changes to <I>y</I> represent small enhancements and
|
|
bug fixes that retain backward compatibility.
|
|
The value of this variable is returned by the <B><A HREF="../TkCmd/info.htm">info tclversion</A></B>
|
|
command.
|
|
|
|
<P></DL>
|
|
<H3><A NAME="M46">SEE ALSO</A></H3>
|
|
<B><A HREF="../TkCmd/eval.htm">eval</A></B>
|
|
<H3><A NAME="M47">KEYWORDS</A></H3>
|
|
<A href="../Keywords/A.htm#arithmetic">arithmetic</A>, <A href="../Keywords/B.htm#bytecode">bytecode</A>, <A href="../Keywords/C.htm#compiler">compiler</A>, <A href="../Keywords/E.htm#error">error</A>, <A href="../Keywords/E.htm#environment">environment</A>, <A href="../Keywords/P.htm#POSIX">POSIX</A>, <A href="../Keywords/P.htm#precision">precision</A>, <A href="../Keywords/S.htm#subprocess">subprocess</A>, <A href="../Keywords/V.htm#variables">variables</A>
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|
<HR><PRE>
|
|
<A HREF="../copyright.htm">Copyright</A> © 1993 The Regents of the University of California.
|
|
<A HREF="../copyright.htm">Copyright</A> © 1994-1997 Sun Microsystems, Inc.
|
|
<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
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</BODY></HTML>
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