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Tcl_SubstObj(3) Tcl Library Procedures Tcl_SubstObj(3)
Tcl_SubstObj - perform substitutions on Tcl values
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
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_BACKSLASHES are currently
supported, and TCL_SUBST_ALL is
provided as a convenience for the
common case where all substitutions
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
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
backslash substitution, command substitution, variable substitution
Tcl 8.4 Tcl_SubstObj(3)