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Tcl_SubstObj(3) 	     Tcl Library Procedures		 Tcl_SubstObj(3)

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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 er-
					ror 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)			OR'ed  combination  of	flag  bits  that
					specify  which substitutions to perform.
					The	 flags	     TCL_SUBST_COMMANDS,
					TCL_SUBST_VARIABLES  and TCL_SUBST_BACK-
					SLASHES  are  currently  supported,  and
					TCL_SUBST_ALL  is  provided  as a conve-
					nience 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  con-
     tained 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 er-
     ror 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 evalu-
     ating  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(n)

KEYWORDS
     backslash substitution, command substitution, variable substitution

Tcl				       8.4			 Tcl_SubstObj(3)

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