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Tcl_CreateAlias(3tcl) Tcl Library Procedures Tcl_CreateAlias(3tcl)


NAME

Tcl_IsSafe, Tcl_MakeSafe, Tcl_CreateChild, Tcl_GetChild, Tcl_GetParent, Tcl_GetInterpPath, Tcl_CreateAlias, Tcl_CreateAliasObj, Tcl_GetAlias, Tcl_GetAliasObj, Tcl_ExposeCommand, Tcl_HideCommand - manage multiple Tcl interpreters, aliases and hidden commands

SYNOPSIS

#include <tcl.h>

int
Tcl_IsSafe(interp)

int
Tcl_MakeSafe(interp)

Tcl_Interp *
Tcl_CreateChild(interp, name, isSafe)

Tcl_Interp *
Tcl_GetChild(interp, name)

Tcl_Interp *
Tcl_GetParent(interp)

int
Tcl_GetInterpPath(interp, childInterp)

int
Tcl_CreateAlias(childInterp, childCmd, targetInterp, targetCmd,
                argc, argv)

int
Tcl_CreateAliasObj(childInterp, childCmd, targetInterp, targetCmd,
                   objc, objv)

int
Tcl_GetAlias(interp, childCmd, targetInterpPtr, targetCmdPtr,
             argcPtr, argvPtr)

int
Tcl_GetAliasObj(interp, childCmd, targetInterpPtr, targetCmdPtr,
                objcPtr, objvPtr)

int
Tcl_ExposeCommand(interp, hiddenCmdName, cmdName)

int
Tcl_HideCommand(interp, cmdName, hiddenCmdName)

ARGUMENTS

Tcl_Interp *interp (in)
Interpreter in which to execute the specified command.
const char *name (in)
Name of child interpreter to create or manipulate.
int isSafe (in)
If non-zero, a “safe” child that is suitable for running untrusted code is created, otherwise a trusted child is created.
Tcl_Interp *childInterp (in)
Interpreter to use for creating the source command for an alias (see below).
const char *childCmd (in)
Name of source command for alias.
Tcl_Interp *targetInterp (in)
Interpreter that contains the target command for an alias.
const char *targetCmd (in)
Name of target command for alias in targetInterp.
int argc (in)
Count of additional arguments to pass to the alias command.
const char *const *argv (in)
Vector of strings, the additional arguments to pass to the alias command. This storage is owned by the caller.
int objc (in)
Count of additional value arguments to pass to the aliased command.
Tcl_Obj **objv (in)
Vector of Tcl_Obj structures, the additional value arguments to pass to the aliased command. This storage is owned by the caller.
Tcl_Interp **targetInterpPtr (in)
Pointer to location to store the address of the interpreter where a target command is defined for an alias.
const char **targetCmdPtr (out)
Pointer to location to store the address of the name of the target command for an alias.
int *argcPtr (out)
Pointer to location to store count of additional arguments to be passed to the alias. The location is in storage owned by the caller.
const char ***argvPtr (out)
Pointer to location to store a vector of strings, the additional arguments to pass to an alias. The location is in storage owned by the caller, the vector of strings is owned by the called function.
int *objcPtr (out)
Pointer to location to store count of additional value arguments to be passed to the alias. The location is in storage owned by the caller.
Tcl_Obj ***objvPtr (out)
Pointer to location to store a vector of Tcl_Obj structures, the additional arguments to pass to an alias command. The location is in storage owned by the caller, the vector of Tcl_Obj structures is owned by the called function.
const char *cmdName (in)
Name of an exposed command to hide or create.
const char *hiddenCmdName (in)
Name under which a hidden command is stored and with which it can be exposed or invoked.

    

DESCRIPTION

These procedures are intended for access to the multiple interpreter facility from inside C programs. They enable managing multiple interpreters in a hierarchical relationship, and the management of aliases, commands that when invoked in one interpreter execute a command in another interpreter. The return value for those procedures that return an int is either TCL_OK or TCL_ERROR. If TCL_ERROR is returned then the interpreter's result contains an error message.

Tcl_CreateChild creates a new interpreter as a child of interp. It also creates a child command named name in interp which allows interp to manipulate the new child. If isSafe is zero, the command creates a trusted child in which Tcl code has access to all the Tcl commands. If it is 1, the command creates a “safe” child in which Tcl code has access only to set of Tcl commands defined as “Safe Tcl”; see the manual entry for the Tcl interp command for details. If the creation of the new child interpreter failed, NULL is returned.

Tcl_IsSafe returns 1 if interp is “safe” (was created with the TCL_SAFE_INTERPRETER flag specified), 0 otherwise.

Tcl_MakeSafe marks interp as “safe”, so that future calls to Tcl_IsSafe will return 1. It also removes all known potentially-unsafe core functionality (both commands and variables) from interp. However, it cannot know what parts of an extension or application are safe and does not make any attempt to remove those parts, so safety is not guaranteed after calling Tcl_MakeSafe. Callers will want to take care with their use of Tcl_MakeSafe to avoid false claims of safety. For many situations, Tcl_CreateChild may be a better choice, since it creates interpreters in a known-safe state.

Tcl_GetChild returns a pointer to a child interpreter of interp. The child interpreter is identified by name. If no such child interpreter exists, NULL is returned.

Tcl_GetParent returns a pointer to the parent interpreter of interp. If interp has no parent (it is a top-level interpreter) then NULL is returned.

Tcl_GetInterpPath stores in the result of interp the relative path between interp and childInterp; childInterp must be a child of interp. If the computation of the relative path succeeds, TCL_OK is returned, else TCL_ERROR is returned and an error message is stored as the result of interp.

Tcl_CreateAlias creates a command named childCmd in childInterp that when invoked, will cause the command targetCmd to be invoked in targetInterp. The arguments specified by the strings contained in argv are always prepended to any arguments supplied in the invocation of childCmd and passed to targetCmd. This operation returns TCL_OK if it succeeds, or TCL_ERROR if it fails; in that case, an error message is left in the value result of childInterp. Note that there are no restrictions on the ancestry relationship (as created by Tcl_CreateChild) between childInterp and targetInterp. Any two interpreters can be used, without any restrictions on how they are related.

Tcl_CreateAliasObj is similar to Tcl_CreateAlias except that it takes a vector of values to pass as additional arguments instead of a vector of strings.

Tcl_GetAlias returns information about an alias aliasName in interp. Any of the result fields can be NULL, in which case the corresponding datum is not returned. If a result field is non-NULL, the address indicated is set to the corresponding datum. For example, if targetNamePtr is non-NULL it is set to a pointer to the string containing the name of the target command.

Tcl_GetAliasObj is similar to Tcl_GetAlias except that it returns a pointer to a vector of Tcl_Obj structures instead of a vector of strings.

Tcl_ExposeCommand moves the command named hiddenCmdName from the set of hidden commands to the set of exposed commands, putting it under the name cmdName. HiddenCmdName must be the name of an existing hidden command, or the operation will return TCL_ERROR and leave an error message as the result of interp. If an exposed command named cmdName already exists, the operation returns TCL_ERROR and leaves an error message as the result of interp. If the operation succeeds, it returns TCL_OK. After executing this command, attempts to use cmdName in any script evaluation mechanism will again succeed.

Tcl_HideCommand moves the command named cmdName from the set of exposed commands to the set of hidden commands, under the name hiddenCmdName. CmdName must be the name of an existing exposed command, or the operation will return TCL_ERROR and leave an error message as the result of interp. Currently both cmdName and hiddenCmdName must not contain namespace qualifiers, or the operation will return TCL_ERROR and leave an error message as the result of interp. The CmdName will be looked up in the global namespace, and not relative to the current namespace, even if the current namespace is not the global one. If a hidden command whose name is hiddenCmdName already exists, the operation also returns TCL_ERROR and an error message is left as the result of interp. If the operation succeeds, it returns TCL_OK. After executing this command, attempts to use cmdName in any script evaluation mechanism will fail.

For a description of the Tcl interface to multiple interpreters, see interp(3tcl).

REFERENCE COUNT MANAGEMENT

Tcl_CreateAliasObj increments the reference counts of the values in its objv argument. (That reference lasts the same length of time as the owning alias.)

Tcl_GetAliasObj returns (via its objvPtr argument) a pointer to values that it holds a reference to.

SEE ALSO

interp(3tcl)

KEYWORDS

alias, command, exposed commands, hidden commands, interpreter, invoke, parent, child
7.6 Tcl