Tcl_SubstObj(3) Tcl Library Procedures Tcl_SubstObj(3) 







Tcl_SubstObj - perform substitutions on Tcl objects








#include <tcl.h>

Tcl_Obj *
Tcl_SubstObj(interp, objPtr, flags)









  
Tcl_Interp *interp (in)

  
Interpreter in which to execute Tcl scripts and lookup variables. If an
      error occurs, the interpreter's result is modified to hold an error
      message.

  
Tcl_Obj *objPtr (in)

  
A Tcl object containing the string to perform substitutions on.

  
int flags (in)

  
ORed combination of flag bits that specify which substitutions to perform.
      The flags TCL_SUBST_COMMANDS, TCL_SUBST_VARIABLES and
      TCL_SUBST_BACKSLASHES are currently supported, and
      TCL_SUBST_ALL is provided as a convenience for the common case
      where all substitutions are desired.
    
    

    

  










The Tcl_SubstObj function is used to perform substitutions
    on strings in the fashion of the subst command. It gets the value of
    the string contained in objPtr and scans it, copying characters and
    performing the chosen substitutions as it goes to an output object which is
    returned as the result of the function. In the event of an error occurring
    during the execution of a command or variable substitution, the function
    returns NULL and an error message is left in interp's result.


Three kinds of substitutions are supported. When the
    TCL_SUBST_BACKSLASHES bit is set in flags, sequences that look
    like backslash substitutions for Tcl commands are replaced by their
    corresponding character.


When the TCL_SUBST_VARIABLES bit is set in flags,
    sequences that look like variable substitutions for Tcl commands are
    replaced by the contents of the named variable.


When the TCL_SUBST_COMMANDS bit is set in flags,
    sequences that look like command substitutions for Tcl commands are replaced
    by the result of evaluating that script. Where an uncaught “continue
    exception” occurs during the evaluation of a command substitution, an
    empty string is substituted for the command. Where an uncaught “break
    exception” occurs during the evaluation of a command substitution,
    the result of the whole substitution on objPtr will be truncated at
    the point immediately before the start of the command substitution, and no
    characters will be added to the result or substitutions performed after that
    point.








subst(n)








backslash substitution, command substitution, variable
    substitution







  

    8.4
    Tcl