1 | '\" |
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2 | '\" Copyright (c) 1989-1993 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: CrtCommand.3,v 1.14 2007/12/13 15:22:30 dgp Exp $ |
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9 | '\" |
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10 | .so man.macros |
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11 | .TH Tcl_CreateCommand 3 "" Tcl "Tcl Library Procedures" |
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12 | .BS |
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13 | .SH NAME |
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14 | Tcl_CreateCommand \- implement new commands in C |
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15 | .SH SYNOPSIS |
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16 | .nf |
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17 | \fB#include <tcl.h>\fR |
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18 | .sp |
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19 | Tcl_Command |
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20 | \fBTcl_CreateCommand\fR(\fIinterp, cmdName, proc, clientData, deleteProc\fR) |
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21 | .SH ARGUMENTS |
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22 | .AS Tcl_CmdDeleteProc *deleteProc |
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23 | .AP Tcl_Interp *interp in |
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24 | Interpreter in which to create new command. |
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25 | .AP "const char" *cmdName in |
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26 | Name of command. |
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27 | .AP Tcl_CmdProc *proc in |
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28 | Implementation of new command: \fIproc\fR will be called whenever |
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29 | \fIcmdName\fR is invoked as a command. |
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30 | .AP ClientData clientData in |
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31 | Arbitrary one-word value to pass to \fIproc\fR and \fIdeleteProc\fR. |
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32 | .AP Tcl_CmdDeleteProc *deleteProc in |
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33 | Procedure to call before \fIcmdName\fR is deleted from the interpreter; |
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34 | allows for command-specific cleanup. If NULL, then no procedure is |
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35 | called before the command is deleted. |
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36 | .BE |
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37 | |
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38 | .SH DESCRIPTION |
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39 | .PP |
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40 | \fBTcl_CreateCommand\fR defines a new command in \fIinterp\fR and associates |
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41 | it with procedure \fIproc\fR such that whenever \fIcmdName\fR is |
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42 | invoked as a Tcl command (via a call to \fBTcl_Eval\fR) the Tcl interpreter |
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43 | will call \fIproc\fR to process the command. |
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44 | It differs from \fBTcl_CreateObjCommand\fR in that a new string-based |
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45 | command is defined; |
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46 | that is, a command procedure is defined that takes an array of |
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47 | argument strings instead of objects. |
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48 | The object-based command procedures registered by \fBTcl_CreateObjCommand\fR |
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49 | can execute significantly faster than the string-based command procedures |
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50 | defined by \fBTcl_CreateCommand\fR. |
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51 | This is because they take Tcl objects as arguments |
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52 | and those objects can retain an internal representation that |
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53 | can be manipulated more efficiently. |
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54 | Also, Tcl's interpreter now uses objects internally. |
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55 | In order to invoke a string-based command procedure |
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56 | registered by \fBTcl_CreateCommand\fR, |
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57 | it must generate and fetch a string representation |
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58 | from each argument object before the call |
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59 | and create a new Tcl object to hold the string result returned by the |
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60 | string-based command procedure. |
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61 | New commands should be defined using \fBTcl_CreateObjCommand\fR. |
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62 | We support \fBTcl_CreateCommand\fR for backwards compatibility. |
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63 | .PP |
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64 | The procedures \fBTcl_DeleteCommand\fR, \fBTcl_GetCommandInfo\fR, |
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65 | and \fBTcl_SetCommandInfo\fR are used in conjunction with |
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66 | \fBTcl_CreateCommand\fR. |
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67 | .PP |
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68 | \fBTcl_CreateCommand\fR will delete an existing command \fIcmdName\fR, |
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69 | if one is already associated with the interpreter. |
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70 | It returns a token that may be used to refer |
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71 | to the command in subsequent calls to \fBTcl_GetCommandName\fR. |
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72 | If \fIcmdName\fR contains any \fB::\fR namespace qualifiers, |
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73 | then the command is added to the specified namespace; |
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74 | otherwise the command is added to the global namespace. |
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75 | If \fBTcl_CreateCommand\fR is called for an interpreter that is in |
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76 | the process of being deleted, then it does not create a new command |
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77 | and it returns NULL. |
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78 | \fIProc\fR should have arguments and result that match the type |
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79 | \fBTcl_CmdProc\fR: |
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80 | .CS |
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81 | typedef int Tcl_CmdProc( |
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82 | ClientData \fIclientData\fR, |
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83 | Tcl_Interp *\fIinterp\fR, |
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84 | int \fIargc\fR, |
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85 | const char *\fIargv\fR[]); |
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86 | .CE |
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87 | When \fIproc\fR is invoked the \fIclientData\fR and \fIinterp\fR |
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88 | parameters will be copies of the \fIclientData\fR and \fIinterp\fR |
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89 | arguments given to \fBTcl_CreateCommand\fR. |
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90 | Typically, \fIclientData\fR points to an application-specific |
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91 | data structure that describes what to do when the command procedure |
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92 | is invoked. \fIArgc\fR and \fIargv\fR describe the arguments to |
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93 | the command, \fIargc\fR giving the number of arguments (including |
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94 | the command name) and \fIargv\fR giving the values of the arguments |
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95 | as strings. The \fIargv\fR array will contain \fIargc\fR+1 values; |
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96 | the first \fIargc\fR values point to the argument strings, and the |
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97 | last value is NULL. |
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98 | Note that the argument strings should not be modified as they may |
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99 | point to constant strings or may be shared with other parts of the |
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100 | interpreter. |
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101 | .PP |
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102 | Note that the argument strings are encoded in normalized UTF-8 since |
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103 | version 8.1 of Tcl. |
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104 | .PP |
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105 | \fIProc\fR must return an integer code that is expected to be one of |
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106 | \fBTCL_OK\fR, \fBTCL_ERROR\fR, \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or |
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107 | \fBTCL_CONTINUE\fR. See the Tcl overview man page |
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108 | for details on what these codes mean. Most normal commands will only |
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109 | return \fBTCL_OK\fR or \fBTCL_ERROR\fR. In addition, \fIproc\fR must set |
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110 | the interpreter result to point to a string value; |
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111 | in the case of a \fBTCL_OK\fR return code this gives the result |
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112 | of the command, and in the case of \fBTCL_ERROR\fR it gives an error message. |
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113 | The \fBTcl_SetResult\fR procedure provides an easy interface for setting |
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114 | the return value; for complete details on how the interpreter result |
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115 | field is managed, see the \fBTcl_Interp\fR man page. |
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116 | Before invoking a command procedure, |
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117 | \fBTcl_Eval\fR sets the interpreter result to point to an empty string, |
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118 | so simple commands can return an empty result by doing nothing at all. |
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119 | .PP |
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120 | The contents of the \fIargv\fR array belong to Tcl and are not |
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121 | guaranteed to persist once \fIproc\fR returns: \fIproc\fR should |
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122 | not modify them, nor should it set the interpreter result to point |
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123 | anywhere within the \fIargv\fR values. |
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124 | Call \fBTcl_SetResult\fR with status \fBTCL_VOLATILE\fR if you want |
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125 | to return something from the \fIargv\fR array. |
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126 | .PP |
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127 | \fIDeleteProc\fR will be invoked when (if) \fIcmdName\fR is deleted. |
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128 | This can occur through a call to \fBTcl_DeleteCommand\fR or \fBTcl_DeleteInterp\fR, |
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129 | or by replacing \fIcmdName\fR in another call to \fBTcl_CreateCommand\fR. |
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130 | \fIDeleteProc\fR is invoked before the command is deleted, and gives the |
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131 | application an opportunity to release any structures associated |
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132 | with the command. \fIDeleteProc\fR should have arguments and |
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133 | result that match the type \fBTcl_CmdDeleteProc\fR: |
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134 | .CS |
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135 | typedef void Tcl_CmdDeleteProc( |
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136 | ClientData \fIclientData\fR); |
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137 | .CE |
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138 | The \fIclientData\fR argument will be the same as the \fIclientData\fR |
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139 | argument passed to \fBTcl_CreateCommand\fR. |
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140 | |
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141 | .SH "SEE ALSO" |
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142 | Tcl_CreateObjCommand, Tcl_DeleteCommand, Tcl_GetCommandInfo, Tcl_SetCommandInfo, Tcl_GetCommandName, Tcl_SetObjResult |
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143 | |
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144 | .SH KEYWORDS |
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145 | bind, command, create, delete, interpreter, namespace |
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