tcl_substobj(3) [opendarwin man page]
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 inter- preter'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_COM- MANDS, TCL_SUBST_VARIABLES and TCL_SUBST_BACKSLASHES are currently supported, and TCL_SUBST_ALL is pro- vided 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, 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 substi- tutions 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 con- tents of the named variable. When th 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(n) KEYWORDS
backslash substitution, command substitution, variable substitution Tcl 8.4 Tcl_SubstObj(3)
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subst(n) Tcl Built-In Commands subst(n) __________________________________________________________________________________________________________________________________________________ NAME
subst - Perform backslash, command, and variable substitutions SYNOPSIS
subst ?-nobackslashes? ?-nocommands? ?-novariables? string _________________________________________________________________ DESCRIPTION
This command performs variable substitutions, command substitutions, and backslash substitutions on its string argument and returns the fully-substituted result. The substitutions are performed in exactly the same way as for Tcl commands. As a result, the string argument is actually substituted twice, once by the Tcl parser in the usual fashion for Tcl commands, and again by the subst command. If any of the -nobackslashes, -nocommands, or -novariables are specified, then the corresponding substitutions are not performed. For example, if -nocommands is specified, command substitution is not performed: open and close brackets are treated as ordinary characters with no special interpretation. Note that the substitution of one kind can include substitution of other kinds. For example, even when the -novariables option is speci- fied, command substitution is performed without restriction. This means that any variable substitution necessary to complete the command substitution will still take place. Likewise, any command substitution necessary to complete a variable substitution will take place, even when -nocommands is specified. See the EXAMPLES below. If an error occurs during substitution, then subst will return that error. If a break exception occurs during command or variable substi- tution, the result of the whole substitution will be the string (as substituted) up to the start of the substitution that raised the excep- tion. If a continue exception occurs during the evaluation of a command or variable substitution, an empty string will be substituted for that entire command or variable substitution (as long as it is well-formed Tcl.) If a return exception occurs, or any other return code is returned during command or variable substitution, then the returned value is substituted for that substitution. See the EXAMPLES below. In this way, all exceptional return codes are "caught" by subst. The subst command itself will either return an error, or will complete successfully. EXAMPLES
When it performs its substitutions, subst does not give any special treatment to double quotes or curly braces (except within command sub- stitutions) so the script set a 44 subst {xyz {$a}} returns "xyz {44}", not "xyz {$a}" and the script set a "p} q {r" subst {xyz {$a}} returns "xyz {p} q {r}", not "xyz {p} q {r}". When command substitution is performed, it includes any variable substitution necessary to evaluate the script. set a 44 subst -novariables {$a [format $a]} returns "$a 44", not "$a $a". Similarly, when variable substitution is performed, it includes any command substitution necessary to retrieve the value of the variable. proc b {} {return c} array set a {c c [b] tricky} subst -nocommands {[b] $a([b])} returns "[b] c", not "[b] tricky". The continue and break exceptions allow command substitutions to prevent substitution of the rest of the command substitution and the rest of string respectively, giving script authors more options when processing text using subst. For example, the script subst {abc,[break],def} returns "abc,", not "abc,,def" and the script subst {abc,[continue;expr {1+2}],def} returns "abc,,def", not "abc,3,def". Other exceptional return codes substitute the returned value subst {abc,[return foo;expr {1+2}],def} returns "abc,foo,def", not "abc,3,def" and subst {abc,[return -code 10 foo;expr {1+2}],def} also returns "abc,foo,def", not "abc,3,def". SEE ALSO
Tcl(n), eval(n), break(n), continue(n) KEYWORDS
backslash substitution, command substitution, variable substitution Tcl 7.4 subst(n)