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Import Tcl 8.6.11

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Steve Dower
2021-03-30 00:51:39 +01:00
parent 3bb8e3e086
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doc/interp.n
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@@ -5,7 +5,7 @@
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\"
.TH interp n 8.6 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
@@ -19,18 +19,18 @@ interp \- Create and manipulate Tcl interpreters
.PP
This command makes it possible to create one or more new Tcl
interpreters that co-exist with the creating interpreter in the
same application. The creating interpreter is called the \fImaster\fR
and the new interpreter is called a \fIslave\fR.
A master can create any number of slaves, and each slave can
itself create additional slaves for which it is master, resulting
same application. The creating interpreter is called the \fIparent\fR
and the new interpreter is called a \fIchild\fR.
A parent can create any number of children, and each child can
itself create additional children for which it is parent, resulting
in a hierarchy of interpreters.
.PP
Each interpreter is independent from the others: it has its own name
space for commands, procedures, and global variables.
A master interpreter may create connections between its slaves and
A parent interpreter may create connections between its children and
itself using a mechanism called an \fIalias\fR. An \fIalias\fR is
a command in a slave interpreter which, when invoked, causes a
command to be invoked in its master interpreter or in another slave
a command in a child interpreter which, when invoked, causes a
command to be invoked in its parent interpreter or in another child
interpreter. The only other connections between interpreters are
through environment variables (the \fBenv\fR variable), which are
normally shared among all interpreters in the application,
@@ -41,7 +41,7 @@ share files and to transfer references to open files from one interpreter
to another.
.PP
The \fBinterp\fR command also provides support for \fIsafe\fR
interpreters. A safe interpreter is a slave whose functions have
interpreters. A safe interpreter is a child whose functions have
been greatly restricted, so that it is safe to execute untrusted
scripts without fear of them damaging other interpreters or the
application's environment. For example, all IO channel creation
@@ -54,18 +54,18 @@ instead, it is \fIhidden\fR, so that only trusted interpreters can obtain
access to it. For a detailed explanation of hidden commands, see
\fBHIDDEN COMMANDS\fR, below.
The alias mechanism can be used for protected communication (analogous to a
kernel call) between a slave interpreter and its master.
kernel call) between a child interpreter and its parent.
See \fBALIAS INVOCATION\fR, below, for more details
on how the alias mechanism works.
.PP
A qualified interpreter name is a proper Tcl lists containing a subset of its
A qualified interpreter name is a proper Tcl list containing a subset of its
ancestors in the interpreter hierarchy, terminated by the string naming the
interpreter in its immediate master. Interpreter names are relative to the
interpreter in its immediate parent. Interpreter names are relative to the
interpreter in which they are used. For example, if
.QW \fBa\fR
is a slave of the current interpreter and it has a slave
is a child of the current interpreter and it has a child
.QW \fBa1\fR ,
which in turn has a slave
which in turn has a child
.QW \fBa11\fR ,
the qualified name of
.QW \fBa11\fR
@@ -77,14 +77,14 @@ is the list
The \fBinterp\fR command, described below, accepts qualified interpreter
names as arguments; the interpreter in which the command is being evaluated
can always be referred to as \fB{}\fR (the empty list or string). Note that
it is impossible to refer to a master (ancestor) interpreter by name in a
slave interpreter except through aliases. Also, there is no global name by
it is impossible to refer to a parent (ancestor) interpreter by name in a
child interpreter except through aliases. Also, there is no global name by
which one can refer to the first interpreter created in an application.
Both restrictions are motivated by safety concerns.
.SH "THE INTERP COMMAND"
.PP
The \fBinterp\fR command is used to create, delete, and manipulate
slave interpreters, and to share or transfer
child interpreters, and to share or transfer
channels between interpreters. It can have any of several forms, depending
on the \fIsubcommand\fR argument:
.TP
@@ -94,11 +94,11 @@ Returns a Tcl list whose elements are the \fItargetCmd\fR and
\fIarg\fRs associated with the alias represented by \fIsrcToken\fR
(this is the value returned when the alias was
created; it is possible that the name of the source command in the
slave is different from \fIsrcToken\fR).
child is different from \fIsrcToken\fR).
.TP
\fBinterp\fR \fBalias\fR \fIsrcPath\fR \fIsrcToken\fR \fB{}\fR
.
Deletes the alias for \fIsrcToken\fR in the slave interpreter identified by
Deletes the alias for \fIsrcToken\fR in the child interpreter identified by
\fIsrcPath\fR.
\fIsrcToken\fR refers to the value returned when the alias
was created; if the source command has been renamed, the renamed
@@ -106,9 +106,9 @@ command will be deleted.
.TP
\fBinterp\fR \fBalias\fR \fIsrcPath\fR \fIsrcCmd\fR \fItargetPath\fR \fItargetCmd \fR?\fIarg arg ...\fR?
.
This command creates an alias between one slave and another (see the
\fBalias\fR slave command below for creating aliases between a slave
and its master). In this command, either of the slave interpreters
This command creates an alias between one child and another (see the
\fBalias\fR child command below for creating aliases between a child
and its parent). In this command, either of the child interpreters
may be anywhere in the hierarchy of interpreters under the interpreter
invoking the command.
\fISrcPath\fR and \fIsrcCmd\fR identify the source of the alias.
@@ -117,9 +117,9 @@ interpreter. For example,
.QW "\fBa b\fR"
identifies an interpreter
.QW \fBb\fR ,
which is a slave of interpreter
which is a child of interpreter
.QW \fBa\fR ,
which is a slave of the invoking interpreter. An empty list specifies
which is a child of the invoking interpreter. An empty list specifies
the interpreter invoking the command. \fIsrcCmd\fR gives the name of
a new command, which will be created in the source interpreter.
\fITargetPath\fR and \fItargetCmd\fR specify a target interpreter
@@ -171,33 +171,33 @@ used.
.TP
\fBinterp\fR \fBcreate \fR?\fB\-safe\fR? ?\fB\-\|\-\fR? ?\fIpath\fR?
.
Creates a slave interpreter identified by \fIpath\fR and a new command,
called a \fIslave command\fR. The name of the slave command is the last
component of \fIpath\fR. The new slave interpreter and the slave command
Creates a child interpreter identified by \fIpath\fR and a new command,
called a \fIchild command\fR. The name of the child command is the last
component of \fIpath\fR. The new child interpreter and the child command
are created in the interpreter identified by the path obtained by removing
the last component from \fIpath\fR. For example, if \fIpath\fR is \fBa b
c\fR then a new slave interpreter and slave command named \fBc\fR are
c\fR then a new child interpreter and child command named \fBc\fR are
created in the interpreter identified by the path \fBa b\fR.
The slave command may be used to manipulate the new interpreter as
The child command may be used to manipulate the new interpreter as
described below. If \fIpath\fR is omitted, Tcl creates a unique name of the
form \fBinterp\fIx\fR, where \fIx\fR is an integer, and uses it for the
interpreter and the slave command. If the \fB\-safe\fR switch is specified
(or if the master interpreter is a safe interpreter), the new slave
interpreter and the child command. If the \fB\-safe\fR switch is specified
(or if the parent interpreter is a safe interpreter), the new child
interpreter will be created as a safe interpreter with limited
functionality; otherwise the slave will include the full set of Tcl
functionality; otherwise the child will include the full set of Tcl
built-in commands and variables. The \fB\-\|\-\fR switch can be used to
mark the end of switches; it may be needed if \fIpath\fR is an unusual
value such as \fB\-safe\fR. The result of the command is the name of the
new interpreter. The name of a slave interpreter must be unique among all
the slaves for its master; an error occurs if a slave interpreter by the
given name already exists in this master.
The initial recursion limit of the slave interpreter is set to the
new interpreter. The name of a child interpreter must be unique among all
the children for its parent; an error occurs if a child interpreter by the
given name already exists in this parent.
The initial recursion limit of the child interpreter is set to the
current recursion limit of its parent interpreter.
.TP
\fBinterp\fR \fBdebug \fIpath\fR ?\fB\-frame\fR ?\fIbool\fR??
.
Controls whether frame-level stack information is captured in the
slave interpreter identified by \fIpath\fR. If no arguments are
child interpreter identified by \fIpath\fR. If no arguments are
given, option and current setting are returned. If \fB\-frame\fR
is given, the debug setting is set to the given boolean if provided
and the current setting is returned.
@@ -239,8 +239,8 @@ consistency of the underlying interpreter's state.
\fBinterp\fR \fBdelete \fR?\fIpath ...?\fR
.
Deletes zero or more interpreters given by the optional \fIpath\fR
arguments, and for each interpreter, it also deletes its slaves. The
command also deletes the slave command for each interpreter deleted.
arguments, and for each interpreter, it also deletes its children. The
command also deletes the child command for each interpreter deleted.
For each \fIpath\fR argument, if no interpreter by that name
exists, the command raises an error.
.TP
@@ -248,20 +248,20 @@ exists, the command raises an error.
.
This command concatenates all of the \fIarg\fR arguments in the same
fashion as the \fBconcat\fR command, then evaluates the resulting string as
a Tcl script in the slave interpreter identified by \fIpath\fR. The result
a Tcl script in the child interpreter identified by \fIpath\fR. The result
of this evaluation (including all \fBreturn\fR options,
such as \fB\-errorinfo\fR and \fB\-errorcode\fR information, if an
error occurs) is returned to the invoking interpreter.
Note that the script will be executed in the current context stack frame of the
\fIpath\fR interpreter; this is so that the implementations (in a master
interpreter) of aliases in a slave interpreter can execute scripts in
the slave that find out information about the slave's current state
\fIpath\fR interpreter; this is so that the implementations (in a parent
interpreter) of aliases in a child interpreter can execute scripts in
the child that find out information about the child's current state
and stack frame.
.TP
\fBinterp exists \fIpath\fR
.
Returns \fB1\fR if a slave interpreter by the specified \fIpath\fR
exists in this master, \fB0\fR otherwise. If \fIpath\fR is omitted, the
Returns \fB1\fR if a child interpreter by the specified \fIpath\fR
exists in this parent, \fB0\fR otherwise. If \fIpath\fR is omitted, the
invoking interpreter is used.
.TP
\fBinterp expose \fIpath\fR \fIhiddenName\fR ?\fIexposedCmdName\fR?
@@ -287,7 +287,7 @@ Currently both \fIexposedCmdName\fR and \fIhiddenCmdName\fR can
not contain namespace qualifiers, or an error is raised.
Commands to be hidden by \fBinterp hide\fR are looked up in the global
namespace even if the current namespace is not the global one. This
prevents slaves from fooling a master interpreter into hiding the wrong
prevents children from fooling a parent interpreter into hiding the wrong
command, by making the current namespace be different from the global one.
Hidden commands are explained in more detail in \fBHIDDEN COMMANDS\fR, below.
.TP
@@ -373,9 +373,15 @@ interpreter is destroyed.
.TP
\fBinterp\fR \fBslaves\fR ?\fIpath\fR?
.
Returns a Tcl list of the names of all the slave interpreters associated
Returns a Tcl list of the names of all the child interpreters associated
with the interpreter identified by \fIpath\fR. If \fIpath\fR is omitted,
the invoking interpreter is used.
.VS "TIP 581"
.TP
\fBinterp\fR \fBchildren\fR ?\fIpath\fR?
.
Synonym for . \fBinterp\fR \fBslaves\fR ?\fIpath\fR?
.VE "TIP 581"
.TP
\fBinterp\fR \fBtarget\fR \fIpath alias\fR
.
@@ -393,48 +399,48 @@ The target command does not have to be defined at the time of this invocation.
Causes the IO channel identified by \fIchannelId\fR to become available in
the interpreter identified by \fIdestPath\fR and unavailable in the
interpreter identified by \fIsrcPath\fR.
.SH "SLAVE COMMAND"
.SH "child COMMAND"
.PP
For each slave interpreter created with the \fBinterp\fR command, a
new Tcl command is created in the master interpreter with the same
For each child interpreter created with the \fBinterp\fR command, a
new Tcl command is created in the parent interpreter with the same
name as the new interpreter. This command may be used to invoke
various operations on the interpreter. It has the following
general form:
.PP
.CS
\fIslave command \fR?\fIarg arg ...\fR?
\fIchild command \fR?\fIarg arg ...\fR?
.CE
.PP
\fISlave\fR is the name of the interpreter, and \fIcommand\fR
\fIchild\fR is the name of the interpreter, and \fIcommand\fR
and the \fIarg\fRs determine the exact behavior of the command.
The valid forms of this command are:
.TP
\fIslave \fBaliases\fR
\fIchild \fBaliases\fR
.
Returns a Tcl list whose elements are the tokens of all the
aliases in \fIslave\fR. The tokens correspond to the values returned when
aliases in \fIchild\fR. The tokens correspond to the values returned when
the aliases were created (which may not be the same
as the current names of the commands).
.TP
\fIslave \fBalias \fIsrcToken\fR
\fIchild \fBalias \fIsrcToken\fR
.
Returns a Tcl list whose elements are the \fItargetCmd\fR and
\fIarg\fRs associated with the alias represented by \fIsrcToken\fR
(this is the value returned when the alias was
created; it is possible that the actual source command in the
slave is different from \fIsrcToken\fR).
child is different from \fIsrcToken\fR).
.TP
\fIslave \fBalias \fIsrcToken \fB{}\fR
\fIchild \fBalias \fIsrcToken \fB{}\fR
.
Deletes the alias for \fIsrcToken\fR in the slave interpreter.
Deletes the alias for \fIsrcToken\fR in the child interpreter.
\fIsrcToken\fR refers to the value returned when the alias
was created; if the source command has been renamed, the renamed
command will be deleted.
.TP
\fIslave \fBalias \fIsrcCmd targetCmd \fR?\fIarg ..\fR?
\fIchild \fBalias \fIsrcCmd targetCmd \fR?\fIarg ..\fR?
.
Creates an alias such that whenever \fIsrcCmd\fR is invoked
in \fIslave\fR, \fItargetCmd\fR is invoked in the master.
in \fIchild\fR, \fItargetCmd\fR is invoked in the parent.
The \fIarg\fR arguments will be passed to \fItargetCmd\fR as additional
arguments, prepended before any arguments passed in the invocation of
\fIsrcCmd\fR.
@@ -443,69 +449,69 @@ The command returns a token that uniquely identifies the command created
\fIsrcCmd\fR, even if the command is renamed afterwards. The token may but
does not have to be equal to \fIsrcCmd\fR.
.TP
\fIslave \fBbgerror\fR ?\fIcmdPrefix\fR?
\fIchild \fBbgerror\fR ?\fIcmdPrefix\fR?
.
This command either gets or sets the current background exception handler
for the \fIslave\fR interpreter. If \fIcmdPrefix\fR is
for the \fIchild\fR interpreter. If \fIcmdPrefix\fR is
absent, the current background exception handler is returned, and if it is
present, it is a list of words (of minimum length one) that describes
what to set the interpreter's background exception handler to. See the
\fBBACKGROUND EXCEPTION HANDLING\fR section for more details.
.TP
\fIslave \fBeval \fIarg \fR?\fIarg ..\fR?
\fIchild \fBeval \fIarg \fR?\fIarg ..\fR?
.
This command concatenates all of the \fIarg\fR arguments in
the same fashion as the \fBconcat\fR command, then evaluates
the resulting string as a Tcl script in \fIslave\fR.
the resulting string as a Tcl script in \fIchild\fR.
The result of this evaluation (including all \fBreturn\fR options,
such as \fB\-errorinfo\fR and \fB\-errorcode\fR information, if an
error occurs) is returned to the invoking interpreter.
Note that the script will be executed in the current context stack frame
of \fIslave\fR; this is so that the implementations (in a master
interpreter) of aliases in a slave interpreter can execute scripts in
the slave that find out information about the slave's current state
of \fIchild\fR; this is so that the implementations (in a parent
interpreter) of aliases in a child interpreter can execute scripts in
the child that find out information about the child's current state
and stack frame.
.TP
\fIslave \fBexpose \fIhiddenName \fR?\fIexposedCmdName\fR?
\fIchild \fBexpose \fIhiddenName \fR?\fIexposedCmdName\fR?
.
This command exposes the hidden command \fIhiddenName\fR, eventually bringing
it back under a new \fIexposedCmdName\fR name (this name is currently
accepted only if it is a valid global name space name without any ::),
in \fIslave\fR.
in \fIchild\fR.
If an exposed command with the targeted name already exists, this command
fails.
For more details on hidden commands, see \fBHIDDEN COMMANDS\fR, below.
.TP
\fIslave \fBhide \fIexposedCmdName\fR ?\fIhiddenCmdName\fR?
\fIchild \fBhide \fIexposedCmdName\fR ?\fIhiddenCmdName\fR?
.
This command hides the exposed command \fIexposedCmdName\fR, renaming it to
the hidden command \fIhiddenCmdName\fR, or keeping the same name if the
argument is not given, in the \fIslave\fR interpreter.
argument is not given, in the \fIchild\fR interpreter.
If a hidden command with the targeted name already exists, this command
fails.
Currently both \fIexposedCmdName\fR and \fIhiddenCmdName\fR can
not contain namespace qualifiers, or an error is raised.
Commands to be hidden are looked up in the global
namespace even if the current namespace is not the global one. This
prevents slaves from fooling a master interpreter into hiding the wrong
prevents children from fooling a parent interpreter into hiding the wrong
command, by making the current namespace be different from the global one.
For more details on hidden commands, see \fBHIDDEN COMMANDS\fR, below.
.TP
\fIslave \fBhidden\fR
\fIchild \fBhidden\fR
.
Returns a list of the names of all hidden commands in \fIslave\fR.
Returns a list of the names of all hidden commands in \fIchild\fR.
.TP
\fIslave \fBinvokehidden\fR ?\fI\-option ...\fR? \fIhiddenName \fR?\fIarg ..\fR?
\fIchild \fBinvokehidden\fR ?\fI\-option ...\fR? \fIhiddenName \fR?\fIarg ..\fR?
.
This command invokes the hidden command \fIhiddenName\fR with the
supplied arguments, in \fIslave\fR. No substitutions or evaluations are
supplied arguments, in \fIchild\fR. No substitutions or evaluations are
applied to the arguments. Three \fI\-option\fRs are supported, all
of which start with \fB\-\fR: \fB\-namespace\fR (which takes a single
argument afterwards, \fInsName\fR), \fB\-global\fR, and \fB\-\|\-\fR.
If the \fB\-namespace\fR flag is given, the hidden command is invoked in
the specified namespace in the slave.
the specified namespace in the child.
If the \fB\-global\fR flag is given, the command is invoked at the global
level in the slave; otherwise it is invoked at the current call frame and
level in the child; otherwise it is invoked at the current call frame and
can access local variables in that or outer call frames.
The \fB\-\|\-\fR flag allows the \fIhiddenCmdName\fR argument to start with a
.QW \-
@@ -513,37 +519,37 @@ character, and is otherwise unnecessary.
If both the \fB\-namespace\fR and \fB\-global\fR flags are given, the
\fB\-namespace\fR flag is ignored.
Note that the hidden command will be executed (by default) in the
current context stack frame of \fIslave\fR.
current context stack frame of \fIchild\fR.
For more details on hidden commands,
see \fBHIDDEN COMMANDS\fR, below.
.TP
\fIslave \fBissafe\fR
\fIchild \fBissafe\fR
.
Returns \fB1\fR if the slave interpreter is safe, \fB0\fR otherwise.
Returns \fB1\fR if the child interpreter is safe, \fB0\fR otherwise.
.TP
\fIslave \fBlimit\fR \fIlimitType\fR ?\fI\-option\fR? ?\fIvalue\fR \fI...\fR?
\fIchild \fBlimit\fR \fIlimitType\fR ?\fI\-option\fR? ?\fIvalue\fR \fI...\fR?
.
Sets up, manipulates and queries the configuration of the resource
limit \fIlimitType\fR for the slave interpreter. If no \fI\-option\fR
limit \fIlimitType\fR for the child interpreter. If no \fI\-option\fR
is specified, return the current configuration of the limit. If
\fI\-option\fR is the sole argument, return the value of that option.
Otherwise, a list of \fI\-option\fR/\fIvalue\fR argument pairs must
supplied. See \fBRESOURCE LIMITS\fR below for a more detailed explanation of
what limits and options are supported.
.TP
\fIslave \fBmarktrusted\fR
\fIchild \fBmarktrusted\fR
.
Marks the slave interpreter as trusted. Can only be invoked by a
Marks the child interpreter as trusted. Can only be invoked by a
trusted interpreter. This command does not expose any hidden
commands in the slave interpreter. The command has no effect if the slave
commands in the child interpreter. The command has no effect if the child
is already trusted.
.TP
\fIslave\fR \fBrecursionlimit\fR ?\fInewlimit\fR?
\fIchild\fR \fBrecursionlimit\fR ?\fInewlimit\fR?
.
Returns the maximum allowable nesting depth for the \fIslave\fR interpreter.
If \fInewlimit\fR is specified, the recursion limit in \fIslave\fR will be
Returns the maximum allowable nesting depth for the \fIchild\fR interpreter.
If \fInewlimit\fR is specified, the recursion limit in \fIchild\fR will be
set so that nesting of more than \fInewlimit\fR calls to \fBTcl_Eval()\fR
and related procedures in \fIslave\fR will return an error.
and related procedures in \fIchild\fR will return an error.
The \fInewlimit\fR value is also returned.
The \fInewlimit\fR value must be a positive integer between 1 and the
maximum value of a non-long integer on the platform.
@@ -567,14 +573,14 @@ For example, commands to create files on disk are removed, and the
\fBexec\fR command is removed, since it could be used to cause damage
through subprocesses.
Limited access to these facilities can be provided, by creating
aliases to the master interpreter which check their arguments carefully
aliases to the parent interpreter which check their arguments carefully
and provide restricted access to a safe subset of facilities.
For example, file creation might be allowed in a particular subdirectory
and subprocess invocation might be allowed for a carefully selected and
fixed set of programs.
.PP
A safe interpreter is created by specifying the \fB\-safe\fR switch
to the \fBinterp create\fR command. Furthermore, any slave created
to the \fBinterp create\fR command. Furthermore, any child created
by a safe interpreter will also be safe.
.PP
A safe interpreter is created with exactly the following set of
@@ -661,15 +667,15 @@ including itself.
.SH "ALIAS INVOCATION"
.PP
The alias mechanism has been carefully designed so that it can
be used safely when an untrusted script is executing
in a safe slave and the target of the alias is a trusted
master. The most important thing in guaranteeing safety is to
ensure that information passed from the slave to the master is
never evaluated or substituted in the master; if this were to
occur, it would enable an evil script in the slave to invoke
arbitrary functions in the master, which would compromise security.
be used safely in an untrusted script which is being executed in a
safe interpreter even if the target of the alias is not a safe
interpreter. The most important thing in guaranteeing safety is to
ensure that information passed from the child to the parent is
never evaluated or substituted in the parent; if this were to
occur, it would enable an evil script in the child to invoke
arbitrary functions in the parent, which would compromise security.
.PP
When the source for an alias is invoked in the slave interpreter, the
When the source for an alias is invoked in the child interpreter, the
usual Tcl substitutions are performed when parsing that command.
These substitutions are carried out in the source interpreter just
as they would be for any other command invoked in that interpreter.
@@ -696,8 +702,8 @@ the alias's source command is parsed in the source interpreter.
When writing the \fItargetCmd\fRs for aliases in safe interpreters,
it is very important that the arguments to that command never be
evaluated or substituted, since this would provide an escape
mechanism whereby the slave interpreter could execute arbitrary
code in the master. This in turn would compromise the security
mechanism whereby the child interpreter could execute arbitrary
code in the parent. This in turn would compromise the security
of the system.
.SH "HIDDEN COMMANDS"
.PP
@@ -724,28 +730,28 @@ invoke\fR. Hidden commands and exposed commands reside in separate name
spaces. It is possible to define a hidden command and an exposed command by
the same name within one interpreter.
.PP
Hidden commands in a slave interpreter can be invoked in the body of
procedures called in the master during alias invocation. For example, an
alias for \fBsource\fR could be created in a slave interpreter. When it is
invoked in the slave interpreter, a procedure is called in the master
Hidden commands in a child interpreter can be invoked in the body of
procedures called in the parent during alias invocation. For example, an
alias for \fBsource\fR could be created in a child interpreter. When it is
invoked in the child interpreter, a procedure is called in the parent
interpreter to check that the operation is allowable (e.g. it asks to
source a file that the slave interpreter is allowed to access). The
procedure then it invokes the hidden \fBsource\fR command in the slave
source a file that the child interpreter is allowed to access). The
procedure then it invokes the hidden \fBsource\fR command in the child
interpreter to actually source in the contents of the file. Note that two
commands named \fBsource\fR exist in the slave interpreter: the alias, and
commands named \fBsource\fR exist in the child interpreter: the alias, and
the hidden command.
.PP
Because a master interpreter may invoke a hidden command as part of
Because a parent interpreter may invoke a hidden command as part of
handling an alias invocation, great care must be taken to avoid evaluating
any arguments passed in through the alias invocation.
Otherwise, malicious slave interpreters could cause a trusted master
Otherwise, malicious child interpreters could cause a trusted parent
interpreter to execute dangerous commands on their behalf. See the section
on \fBALIAS INVOCATION\fR for a more complete discussion of this topic.
To help avoid this problem, no substitutions or evaluations are
applied to arguments of \fBinterp invokehidden\fR.
.PP
Safe interpreters are not allowed to invoke hidden commands in themselves
or in their descendants. This prevents safe slaves from gaining access to
or in their descendants. This prevents them from gaining access to
hidden functionality in themselves or their descendants.
.PP
The set of hidden commands in an interpreter can be manipulated by a trusted
@@ -764,12 +770,12 @@ qualifiers, and you must first rename a command in a namespace to the
global namespace before you can hide it.
Commands to be hidden by \fBinterp hide\fR are looked up in the global
namespace even if the current namespace is not the global one. This
prevents slaves from fooling a master interpreter into hiding the wrong
prevents children from fooling a parent interpreter into hiding the wrong
command, by making the current namespace be different from the global one.
.SH "RESOURCE LIMITS"
.PP
Every interpreter has two kinds of resource limits that may be imposed by any
master interpreter upon its slaves. Command limits (of type \fBcommand\fR)
parent interpreter upon its children. Command limits (of type \fBcommand\fR)
restrict the total number of Tcl commands that may be executed by an
interpreter (as can be inspected via the \fBinfo cmdcount\fR command), and
time limits (of type \fBtime\fR) place a limit by which execution within the
@@ -778,7 +784,7 @@ interpreter must complete. Note that time limits are expressed as
\fBafter\fR) because they may be modified after creation.
.PP
When a limit is exceeded for an interpreter, first any handler callbacks
defined by master interpreters are called. If those callbacks increase or
defined by parent interpreters are called. If those callbacks increase or
remove the limit, execution within the (previously) limited interpreter
continues. If the limit is still in force, an error is generated at that point
and normal processing of errors within the interpreter (by the \fBcatch\fR
@@ -835,13 +841,13 @@ This option specifies the number of commands that the interpreter may execute
before triggering the command limit. This option may be the empty string,
which indicates that a command limit is not set for the interpreter.
.PP
Where an interpreter with a resource limit set on it creates a slave
interpreter, that slave interpreter will have resource limits imposed on it
that are at least as restrictive as the limits on the creating master
interpreter. If the master interpreter of the limited master wishes to relax
Where an interpreter with a resource limit set on it creates a child
interpreter, that child interpreter will have resource limits imposed on it
that are at least as restrictive as the limits on the creating parent
interpreter. If the parent interpreter of the limited parent wishes to relax
these conditions, it should hide the \fBinterp\fR command in the child and
then use aliases and the \fBinterp invokehidden\fR subcommand to provide such
access as it chooses to the \fBinterp\fR command to the limited master as
access as it chooses to the \fBinterp\fR command to the limited parent as
necessary.
.SH "BACKGROUND EXCEPTION HANDLING"
.PP
@@ -902,9 +908,9 @@ set i [\fBinterp create\fR]
}
.CE
.SH "SEE ALSO"
bgerror(n), load(n), safe(n), Tcl_CreateSlave(3), Tcl_Eval(3), Tcl_BackgroundException(3)
bgerror(n), load(n), safe(n), Tcl_CreateChild(3), Tcl_Eval(3), Tcl_BackgroundException(3)
.SH KEYWORDS
alias, master interpreter, safe interpreter, slave interpreter
alias, parent interpreter, safe interpreter, child interpreter
'\"Local Variables:
'\"mode: nroff
'\"End: