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1# init.tcl --
2#
3# Default system startup file for Tcl-based applications. Defines
4# "unknown" procedure and auto-load facilities.
5#
6# $Header: /user6/ouster/tcl/scripts/RCS/init.tcl,v 1.7 92/07/25 16:29:36 ouster Exp $ SPRITE (Berkeley)
7#
8# Copyright 1991-1992 Regents of the University of California
9# Permission to use, copy, modify, and distribute this
10# software and its documentation for any purpose and without
11# fee is hereby granted, provided that this copyright
12# notice appears in all copies. The University of California
13# makes no representations about the suitability of this
14# software for any purpose. It is provided "as is" without
15# express or implied warranty.
16#
17
18# unknown:
19# Invoked when a Tcl command is invoked that doesn't exist in the
20# interpreter:
21#
22# 1. See if the autoload facility can locate the command in a
23# Tcl script file. If so, load it and execute it.
24# 2. See if the command exists as an executable UNIX program.
25# If so, "exec" the command.
26# 3. See if the command is a valid abbreviation for another command.
27# if so, invoke the command. However, only permit abbreviations
28# at top-level.
29
30proc unknown args {
31 global auto_noexec auto_noload env unknown_active
32
33 if [info exists unknown_active] {
34 unset unknown_active
35 error "unexpected recursion in \"unknown\" command"
36 }
37 set unknown_active 1
38 set name [lindex $args 0]
39 if ![info exists auto_noload] {
40 if [auto_load $name] {
41 unset unknown_active
42 return [uplevel $args]
43 }
44 }
45 if ![info exists auto_noexec] {
46 if [auto_execok $name] {
47 unset unknown_active
48 return [uplevel exec $args]
49 }
50 }
51 if {([info level] == 1) && ([info script] == "")} {
52 set cmds [info commands $name*]
53 if {[llength $cmds] == 1} {
54 unset unknown_active
55 return [uplevel [lreplace $args 0 0 $cmds]]
56 }
57 if {[llength $cmds] != 0} {
58 unset unknown_active
59 if {$name == ""} {
60 error "empty command name \"\""
61 } else {
62 error "ambiguous command name \"$name\": [lsort $cmds]"
63 }
64 }
65 }
66 unset unknown_active
67 error "invalid command name \"$name\""
68}
69
70# auto_load:
71# Checks a collection of library directories to see if a procedure
72# is defined in one of them. If so, it sources the appropriate
73# library file to create the procedure. Returns 1 if it successfully
74# loaded the procedure, 0 otherwise.
75
76proc auto_load cmd {
77 global auto_index auto_oldpath auto_path env
78 if [info exists auto_index($cmd)] {
79 uplevel #0 source $auto_index($cmd)
80 return 1
81 }
82 if [catch {set path $auto_path}] {
83 if [catch {set path $env(TCLLIBPATH)}] {
84 if [catch {set path [info library]}] {
85 return 0
86 }
87 }
88 }
89 if [info exists auto_oldpath] {
90 if {$auto_oldpath == $path} {
91 return 0
92 }
93 }
94 set auto_oldpath $path
95 catch {unset auto_index}
96 foreach dir $path {
97 set f ""
98 catch {
99 set f [open $dir/tclindex]
100 if {[gets $f] != "# Tcl autoload index file: each line identifies a Tcl"} {
101 puts stdout "Bad id line in file $dir/tclindex"
102 error done
103 }
104 while {[gets $f line] >= 0} {
105 if {([string index $line 0] == "#") || ([llength $line] != 2)} {
106 continue
107 }
108 set name [lindex $line 0]
109 if {![info exists auto_index($name)]} {
110 set auto_index($name) $dir/[lindex $line 1]
111 }
112 }
113 }
114 if {$f != ""} {
115 close $f
116 }
117 }
118 if [info exists auto_index($cmd)] {
119 uplevel #0 source $auto_index($cmd)
120 return 1
121 }
122 return 0
123}
124
125# auto_execok:
126# Returns 1 if there's an executable in the current path for the
127# given name, 0 otherwise. Builds an associative array auto_execs
128# that caches information about previous checks, for speed.
129
130proc auto_execok name {
131 global auto_execs env
132
133 if [info exists auto_execs($name)] {
134 return $auto_execs($name)
135 }
136 set auto_execs($name) 0
137 foreach dir [split $env(PATH) :] {
138 if {[file executable $dir/$name] && ![file isdirectory $dir/$name]} {
139 set auto_execs($name) 1
140 return 1
141 }
142 }
143 return 0
144}
145
146# auto_reset:
147# Destroy all cached information for auto-loading and auto-execution,
148# so that the information gets recomputed the next time it's needed.
149
150proc auto_reset {} {
151 global auto_execs auto_index
152 unset auto_execs auto_index
153}
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