NAME

       Tcl_SubstObj - perform substitutions on Tcl values

SYNOPSIS

       #include <tcl.h>

       Tcl_Obj *
       Tcl_SubstObj(interp, objPtr, flags)

ARGUMENTS

       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   value   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.
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DESCRIPTION

       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 value
       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.

SEE ALSO

       subst(3tcl)

KEYWORDS

       backslash substitution, command substitution, variable substitution