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Diffstat (limited to 'tcl8.6/doc/unknown.n')
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1 files changed, 0 insertions, 91 deletions
diff --git a/tcl8.6/doc/unknown.n b/tcl8.6/doc/unknown.n deleted file mode 100644 index 82dcefc..0000000 --- a/tcl8.6/doc/unknown.n +++ /dev/null @@ -1,91 +0,0 @@ -'\" -'\" Copyright (c) 1993 The Regents of the University of California. -'\" Copyright (c) 1994-1996 Sun Microsystems, Inc. -'\" -'\" See the file "license.terms" for information on usage and redistribution -'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. -'\" -.TH unknown n "" Tcl "Tcl Built-In Commands" -.so man.macros -.BS -'\" Note: do not modify the .SH NAME line immediately below! -.SH NAME -unknown \- Handle attempts to use non-existent commands -.SH SYNOPSIS -\fBunknown \fIcmdName \fR?\fIarg arg ...\fR? -.BE -.SH DESCRIPTION -.PP -This command is invoked by the Tcl interpreter whenever a script -tries to invoke a command that does not exist. The default implementation -of \fBunknown\fR is a library procedure defined when Tcl initializes an -interpreter. You can override the default \fBunknown\fR to change its -functionality, or you can register a new handler for individual namespaces -using the \fBnamespace unknown\fR command. Note that there is no default -implementation of \fBunknown\fR in a safe interpreter. -.PP -If the Tcl interpreter encounters a command name for which there -is not a defined command (in either the current namespace, or the -global namespace), then Tcl checks for the existence of -an unknown handler for the current namespace. By default, this -handler is a command named \fB::unknown\fR. If there is no such -command, then the interpreter returns an error. -If the \fBunknown\fR command exists (or a new handler has been -registered for the current namespace), then it is invoked with -arguments consisting of the fully-substituted name and arguments -for the original non-existent command. -The \fBunknown\fR command typically does things like searching -through library directories for a command procedure with the name -\fIcmdName\fR, or expanding abbreviated command names to full-length, -or automatically executing unknown commands as sub-processes. -In some cases (such as expanding abbreviations) \fBunknown\fR will -change the original command slightly and then (re-)execute it. -The result of the \fBunknown\fR command is used as the result for -the original non-existent command. -.PP -The default implementation of \fBunknown\fR behaves as follows. -It first calls the \fBauto_load\fR library procedure to load the command. -If this succeeds, then it executes the original command with its -original arguments. -If the auto-load fails then \fBunknown\fR calls \fBauto_execok\fR -to see if there is an executable file by the name \fIcmd\fR. -If so, it invokes the Tcl \fBexec\fR command -with \fIcmd\fR and all the \fIargs\fR as arguments. -If \fIcmd\fR cannot be auto-executed, \fBunknown\fR checks to -see if the command was invoked at top-level and outside of any -script. If so, then \fBunknown\fR takes two additional steps. -First, it sees if \fIcmd\fR has one of the following three forms: -\fB!!\fR, \fB!\fIevent\fR, or \fB^\fIold\fB^\fInew\fR?\fB^\fR?. -If so, then \fBunknown\fR carries out history substitution -in the same way that \fBcsh\fR would for these constructs. -Finally, \fBunknown\fR checks to see if \fIcmd\fR is -a unique abbreviation for an existing Tcl command. -If so, it expands the command name and executes the command with -the original arguments. -If none of the above efforts has been able to execute -the command, \fBunknown\fR generates an error return. -If the global variable \fBauto_noload\fR is defined, then the auto-load -step is skipped. -If the global variable \fBauto_noexec\fR is defined then the -auto-exec step is skipped. -Under normal circumstances the return value from \fBunknown\fR -is the return value from the command that was eventually -executed. -.SH EXAMPLE -Arrange for the \fBunknown\fR command to have its standard behavior -except for first logging the fact that a command was not found: -.PP -.CS -# Save the original one so we can chain to it -rename \fBunknown\fR _original_unknown - -# Provide our own implementation -proc \fBunknown\fR args { - puts stderr "WARNING: unknown command: $args" - uplevel 1 [list _original_unknown {*}$args] -} -.CE -.SH "SEE ALSO" -info(n), proc(n), interp(n), library(n), namespace(n) -.SH KEYWORDS -error, non-existent command, unknown |