## Tcl8.6.2/Tk8.6.2 Documentation > Tcl C API, version 8.6.2 > CrtSlave

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  NAME
    Tcl_IsSafe, Tcl_MakeSafe, Tcl_CreateSlave, Tcl_GetSlave, Tcl_GetMaster, 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_CreateSlave(interp, slaveName, isSafe)
    Tcl_Interp *
    Tcl_GetSlave(interp, slaveName)
    Tcl_Interp *
    Tcl_GetMaster(interp)
    int
    Tcl_GetInterpPath(askingInterp, slaveInterp)
    int
    Tcl_CreateAlias(slaveInterp, slaveCmd, targetInterp, targetCmd,
    argc, argv)
    int
    Tcl_CreateAliasObj(slaveInterp, slaveCmd, targetInterp, targetCmd,
    objc, objv)
    int
    Tcl_GetAlias(interp, slaveCmd, targetInterpPtr, targetCmdPtr,
    argcPtr, argvPtr)
    int
    Tcl_GetAliasObj(interp, slaveCmd, targetInterpPtr, targetCmdPtr,
    objcPtr, objvPtr)
    int
    Tcl_ExposeCommand(interp, hiddenCmdName, cmdName)
    int
    Tcl_HideCommand(interp, cmdName, hiddenCmdName)
  ARGUMENTS
  DESCRIPTION
  SEE ALSO
  KEYWORDS

### NAME

Tcl_IsSafe, Tcl_MakeSafe, Tcl_CreateSlave, Tcl_GetSlave, Tcl_GetMaster, 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_CreateSlave(interp, slaveName, isSafe)
Tcl_Interp *
Tcl_GetSlave(interp, slaveName)
Tcl_Interp *
Tcl_GetMaster(interp)
int
Tcl_GetInterpPath(askingInterp, slaveInterp)
int
Tcl_CreateAlias(slaveInterp, slaveCmd, targetInterp, targetCmd,
`` argc, argv)
int
Tcl_CreateAliasObj(slaveInterp, slaveCmd, targetInterp, targetCmd,
`` objc, objv)
int
Tcl_GetAlias(interp, slaveCmd, targetInterpPtr, targetCmdPtr,
`` argcPtr, argvPtr)
int
Tcl_GetAliasObj(interp, slaveCmd, 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 *slaveName (in)
  Name of slave interpreter to create or manipulate.

int isSafe (in)
  If non-zero, a “safe” slave that is suitable for running untrusted code is created, otherwise a trusted slave is created.

Tcl_Interp *slaveInterp (in)
  Interpreter to use for creating the source command for an alias (see below).

const char *slaveCmd (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 result field of the interpreter contains an error message.

Tcl_CreateSlave creates a new interpreter as a slave of interp. It also creates a slave command named slaveName in interp which allows interp to manipulate the new slave. If isSafe is zero, the command creates a trusted slave in which Tcl code has access to all the Tcl commands. If it is 1, the command creates a “safe” slave 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 slave 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_CreateSlave may be a better choice, since it creates interpreters in a known-safe state.

Tcl_GetSlave returns a pointer to a slave interpreter of interp. The slave interpreter is identified by slaveName. If no such slave interpreter exists, NULL is returned.

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

Tcl_GetInterpPath sets the result field in askingInterp to the relative path between askingInterp and slaveInterp; slaveInterp must be a slave of askingInterp. If the computation of the relative path succeeds, TCL_OK is returned, else TCL_ERROR is returned and the result field in askingInterp contains the error message.

Tcl_CreateAlias creates a command named slaveCmd in slaveInterp 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 slaveCmd 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 slaveInterp. Note that there are no restrictions on the ancestry relationship (as created by Tcl_CreateSlave) between slaveInterp 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 in the result field in interp. If an exposed command named cmdName already exists, the operation returns TCL_ERROR and leaves an error message in the value result of interp. If the operation succeeds, it returns TCL_OK. After executing this command, attempts to use cmdName in a call to Tcl_Eval or with the Tcl eval command 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 in the value 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 in the value 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 the result field in interp contains an error message. If the operation succeeds, it returns TCL_OK. After executing this command, attempts to use cmdName in a call to Tcl_Eval or with the Tcl eval command will fail.

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

### SEE ALSO

interp

### KEYWORDS

alias, command, exposed commands, hidden commands, interpreter, invoke, master, slave
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