Tcl_SubstObj(3tcl)

Tcl_SubstObj(3)      Tcl Library Procedures       Tcl_SubstObj(3)

_________________________________________________________________

NAME

     Tcl_SubstObj - perform substitutions on Tcl objects

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  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.
_________________________________________________________________

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,  copy-
     ing 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  func-
     tion  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

Tcl                     Last change: 8.4                        1

Tcl_SubstObj(3)      Tcl Library Procedures       Tcl_SubstObj(3)

     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  substitu-
     tion,  and no characters will be added to the result or sub-
     stitutions performed after that point.

SEE ALSO

     subst(n)

KEYWORDS

     backslash substitution, command substitution, variable  sub-
     stitution

Tcl                     Last change: 8.4                        2