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diff --git a/doc/ParseCmd.3 b/doc/ParseCmd.3 new file mode 100644 index 0000000..667d697 --- /dev/null +++ b/doc/ParseCmd.3 @@ -0,0 +1,467 @@ +'\" +'\" Copyright (c) 1997 Sun Microsystems, Inc. +'\" +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +.TH Tcl_ParseCommand 3 8.3 Tcl "Tcl Library Procedures" +.so man.macros +.BS +.SH NAME +Tcl_ParseCommand, Tcl_ParseExpr, Tcl_ParseBraces, Tcl_ParseQuotedString, Tcl_ParseVarName, Tcl_ParseVar, Tcl_FreeParse, Tcl_EvalTokens, Tcl_EvalTokensStandard \- parse Tcl scripts and expressions +.SH SYNOPSIS +.nf +\fB#include <tcl.h>\fR +.sp +int +\fBTcl_ParseCommand\fR(\fIinterp, start, numBytes, nested, parsePtr\fR) +.sp +int +\fBTcl_ParseExpr\fR(\fIinterp, start, numBytes, parsePtr\fR) +.sp +int +\fBTcl_ParseBraces\fR(\fIinterp, start, numBytes, parsePtr, append, termPtr\fR) +.sp +int +\fBTcl_ParseQuotedString\fR(\fIinterp, start, numBytes, parsePtr, append, termPtr\fR) +.sp +int +\fBTcl_ParseVarName\fR(\fIinterp, start, numBytes, parsePtr, append\fR) +.sp +const char * +\fBTcl_ParseVar\fR(\fIinterp, start, termPtr\fR) +.sp +\fBTcl_FreeParse\fR(\fIusedParsePtr\fR) +.sp +Tcl_Obj * +\fBTcl_EvalTokens\fR(\fIinterp, tokenPtr, numTokens\fR) +.sp +int +\fBTcl_EvalTokensStandard\fR(\fIinterp, tokenPtr, numTokens\fR) +.SH ARGUMENTS +.AS Tcl_Interp *usedParsePtr out +.AP Tcl_Interp *interp out +For procedures other than \fBTcl_FreeParse\fR, \fBTcl_EvalTokens\fR +and \fBTcl_EvalTokensStandard\fR, used only for error reporting; +if NULL, then no error messages are left after errors. +For \fBTcl_EvalTokens\fR and \fBTcl_EvalTokensStandard\fR, +determines the context for evaluating the +script and also is used for error reporting; must not be NULL. +.AP "const char" *start in +Pointer to first character in string to parse. +.AP int numBytes in +Number of bytes in string to parse, not including any terminating null +character. If less than 0 then the script consists of all characters +following \fIstart\fR up to the first null character. +.AP int nested in +Non-zero means that the script is part of a command substitution so an +unquoted close bracket should be treated as a command terminator. If zero, +close brackets have no special meaning. +.AP int append in +Non-zero means that \fI*parsePtr\fR already contains valid tokens; the new +tokens should be appended to those already present. Zero means that +\fI*parsePtr\fR is uninitialized; any information in it is ignored. +This argument is normally 0. +.AP Tcl_Parse *parsePtr out +Points to structure to fill in with information about the parsed +command, expression, variable name, etc. +Any previous information in this structure +is ignored, unless \fIappend\fR is non-zero in a call to +\fBTcl_ParseBraces\fR, \fBTcl_ParseQuotedString\fR, +or \fBTcl_ParseVarName\fR. +.AP "const char" **termPtr out +If not NULL, points to a location where +\fBTcl_ParseBraces\fR, \fBTcl_ParseQuotedString\fR, and +\fBTcl_ParseVar\fR will store a pointer to the character +just after the terminating character (the close-brace, the last +character of the variable name, or the close-quote (respectively)) +if the parse was successful. +.AP Tcl_Parse *usedParsePtr in +Points to structure that was filled in by a previous call to +\fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseVarName\fR, etc. +.BE +.SH DESCRIPTION +.PP +These procedures parse Tcl commands or portions of Tcl commands such as +expressions or references to variables. +Each procedure takes a pointer to a script (or portion thereof) +and fills in the structure pointed to by \fIparsePtr\fR +with a collection of tokens describing the information that was parsed. +The procedures normally return \fBTCL_OK\fR. +However, if an error occurs then they return \fBTCL_ERROR\fR, +leave an error message in \fIinterp\fR's result +(if \fIinterp\fR is not NULL), +and leave nothing in \fIparsePtr\fR. +.PP +\fBTcl_ParseCommand\fR is a procedure that parses Tcl +scripts. Given a pointer to a script, it +parses the first command from the script. If the command was parsed +successfully, \fBTcl_ParseCommand\fR returns \fBTCL_OK\fR and fills in the +structure pointed to by \fIparsePtr\fR with information about the +structure of the command (see below for details). +If an error occurred in parsing the command then +\fBTCL_ERROR\fR is returned, an error message is left in \fIinterp\fR's +result, and no information is left at \fI*parsePtr\fR. +.PP +\fBTcl_ParseExpr\fR parses Tcl expressions. +Given a pointer to a script containing an expression, +\fBTcl_ParseExpr\fR parses the expression. +If the expression was parsed successfully, +\fBTcl_ParseExpr\fR returns \fBTCL_OK\fR and fills in the +structure pointed to by \fIparsePtr\fR with information about the +structure of the expression (see below for details). +If an error occurred in parsing the command then +\fBTCL_ERROR\fR is returned, an error message is left in \fIinterp\fR's +result, and no information is left at \fI*parsePtr\fR. +.PP +\fBTcl_ParseBraces\fR parses a string or command argument +enclosed in braces such as +\fB{hello}\fR or \fB{string \et with \et tabs}\fR +from the beginning of its argument \fIstart\fR. +The first character of \fIstart\fR must be \fB{\fR. +If the braced string was parsed successfully, +\fBTcl_ParseBraces\fR returns \fBTCL_OK\fR, +fills in the structure pointed to by \fIparsePtr\fR +with information about the structure of the string +(see below for details), +and stores a pointer to the character just after the terminating \fB}\fR +in the location given by \fI*termPtr\fR. +If an error occurs while parsing the string +then \fBTCL_ERROR\fR is returned, +an error message is left in \fIinterp\fR's result, +and no information is left at \fI*parsePtr\fR or \fI*termPtr\fR. +.PP +\fBTcl_ParseQuotedString\fR parses a double-quoted string such as +\fB"sum is [expr {$a+$b}]"\fR +from the beginning of the argument \fIstart\fR. +The first character of \fIstart\fR must be \fB\N'34'\fR. +If the double-quoted string was parsed successfully, +\fBTcl_ParseQuotedString\fR returns \fBTCL_OK\fR, +fills in the structure pointed to by \fIparsePtr\fR +with information about the structure of the string +(see below for details), +and stores a pointer to the character just after the terminating \fB\N'34'\fR +in the location given by \fI*termPtr\fR. +If an error occurs while parsing the string +then \fBTCL_ERROR\fR is returned, +an error message is left in \fIinterp\fR's result, +and no information is left at \fI*parsePtr\fR or \fI*termPtr\fR. +.PP +\fBTcl_ParseVarName\fR parses a Tcl variable reference such as +\fB$abc\fR or \fB$x([expr {$index + 1}])\fR from the beginning of its +\fIstart\fR argument. +The first character of \fIstart\fR must be \fB$\fR. +If a variable name was parsed successfully, \fBTcl_ParseVarName\fR +returns \fBTCL_OK\fR and fills in the structure pointed to by +\fIparsePtr\fR with information about the structure of the variable name +(see below for details). If an error +occurs while parsing the command then \fBTCL_ERROR\fR is returned, an +error message is left in \fIinterp\fR's result (if \fIinterp\fR is not +NULL), and no information is left at \fI*parsePtr\fR. +.PP +\fBTcl_ParseVar\fR parse a Tcl variable reference such as \fB$abc\fR +or \fB$x([expr {$index + 1}])\fR from the beginning of its \fIstart\fR +argument. The first character of \fIstart\fR must be \fB$\fR. If +the variable name is parsed successfully, \fBTcl_ParseVar\fR returns a +pointer to the string value of the variable. If an error occurs while +parsing, then NULL is returned and an error message is left in +\fIinterp\fR's result. +.PP +The information left at \fI*parsePtr\fR +by \fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, +\fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR +may include dynamically allocated memory. +If these five parsing procedures return \fBTCL_OK\fR +then the caller must invoke \fBTcl_FreeParse\fR to release +the storage at \fI*parsePtr\fR. +These procedures ignore any existing information in +\fI*parsePtr\fR (unless \fIappend\fR is non-zero), +so if repeated calls are being made to any of them +then \fBTcl_FreeParse\fR must be invoked once after each call. +.PP +\fBTcl_EvalTokensStandard\fR evaluates a sequence of parse tokens from +a Tcl_Parse structure. The tokens typically consist +of all the tokens in a word or all the tokens that make up the index for +a reference to an array variable. \fBTcl_EvalTokensStandard\fR performs the +substitutions requested by the tokens and concatenates the +resulting values. +The return value from \fBTcl_EvalTokensStandard\fR is a Tcl completion +code with one of the values \fBTCL_OK\fR, \fBTCL_ERROR\fR, +\fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or \fBTCL_CONTINUE\fR, or possibly +some other integer value originating in an extension. +In addition, a result value or error message is left in \fIinterp\fR's +result; it can be retrieved using \fBTcl_GetObjResult\fR. +.PP +\fBTcl_EvalTokens\fR differs from \fBTcl_EvalTokensStandard\fR only in +the return convention used: it returns the result in a new Tcl_Obj. +The reference count of the value returned as result has been +incremented, so the caller must +invoke \fBTcl_DecrRefCount\fR when it is finished with the value. +If an error or other exception occurs while evaluating the tokens +(such as a reference to a non-existent variable) then the return value +is NULL and an error message is left in \fIinterp\fR's result. The use +of \fBTcl_EvalTokens\fR is deprecated. +.SH "TCL_PARSE STRUCTURE" +.PP +\fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, +\fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR +return parse information in two data structures, Tcl_Parse and Tcl_Token: +.PP +.CS +typedef struct Tcl_Parse { + const char *\fIcommentStart\fR; + int \fIcommentSize\fR; + const char *\fIcommandStart\fR; + int \fIcommandSize\fR; + int \fInumWords\fR; + Tcl_Token *\fItokenPtr\fR; + int \fInumTokens\fR; + ... +} \fBTcl_Parse\fR; + +typedef struct Tcl_Token { + int \fItype\fR; + const char *\fIstart\fR; + int \fIsize\fR; + int \fInumComponents\fR; +} \fBTcl_Token\fR; +.CE +.PP +The first five fields of a Tcl_Parse structure +are filled in only by \fBTcl_ParseCommand\fR. +These fields are not used by the other parsing procedures. +.PP +\fBTcl_ParseCommand\fR fills in a Tcl_Parse structure +with information that describes one Tcl command and any comments that +precede the command. +If there are comments, +the \fIcommentStart\fR field points to the \fB#\fR character that begins +the first comment and \fIcommentSize\fR indicates the number of bytes +in all of the comments preceding the command, including the newline +character that terminates the last comment. +If the command is not preceded by any comments, \fIcommentSize\fR is 0. +\fBTcl_ParseCommand\fR also sets the \fIcommandStart\fR field +to point to the first character of the first +word in the command (skipping any comments and leading space) and +\fIcommandSize\fR gives the total number of bytes in the command, +including the character pointed to by \fIcommandStart\fR up to and +including the newline, close bracket, or semicolon character that +terminates the command. The \fInumWords\fR field gives the +total number of words in the command. +.PP +All parsing procedures set the remaining fields, +\fItokenPtr\fR and \fInumTokens\fR. +The \fItokenPtr\fR field points to the first in an array of Tcl_Token +structures that describe the components of the entity being parsed. +The \fInumTokens\fR field gives the total number of tokens +present in the array. +Each token contains four fields. +The \fItype\fR field selects one of several token types +that are described below. The \fIstart\fR field +points to the first character in the token and the \fIsize\fR field +gives the total number of characters in the token. Some token types, +such as \fBTCL_TOKEN_WORD\fR and \fBTCL_TOKEN_VARIABLE\fR, consist of +several component tokens, which immediately follow the parent token; +the \fInumComponents\fR field describes how many of these there are. +The \fItype\fR field has one of the following values: +.TP 20 +\fBTCL_TOKEN_WORD\fR +. +This token ordinarily describes one word of a command +but it may also describe a quoted or braced string in an expression. +The token describes a component of the script that is +the result of concatenating together a sequence of subcomponents, +each described by a separate subtoken. +The token starts with the first non-blank +character of the component (which may be a double-quote or open brace) +and includes all characters in the component up to but not including the +space, semicolon, close bracket, close quote, or close brace that +terminates the component. The \fInumComponents\fR field counts the total +number of sub-tokens that make up the word, including sub-tokens +of \fBTCL_TOKEN_VARIABLE\fR and \fBTCL_TOKEN_BS\fR tokens. +.TP +\fBTCL_TOKEN_SIMPLE_WORD\fR +. +This token has the same meaning as \fBTCL_TOKEN_WORD\fR, except that +the word is guaranteed to consist of a single \fBTCL_TOKEN_TEXT\fR +sub-token. The \fInumComponents\fR field is always 1. +.TP +\fBTCL_TOKEN_EXPAND_WORD\fR +. +This token has the same meaning as \fBTCL_TOKEN_WORD\fR, except that +the command parser notes this word began with the expansion +prefix \fB{*}\fR, indicating that after substitution, +the list value of this word should be expanded to form multiple +arguments in command evaluation. This +token type can only be created by Tcl_ParseCommand. +.TP +\fBTCL_TOKEN_TEXT\fR +. +The token describes a range of literal text that is part of a word. +The \fInumComponents\fR field is always 0. +.TP +\fBTCL_TOKEN_BS\fR +. +The token describes a backslash sequence such as \fB\en\fR or \fB\e0xa3\fR. +The \fInumComponents\fR field is always 0. +.TP +\fBTCL_TOKEN_COMMAND\fR +. +The token describes a command whose result must be substituted into +the word. The token includes the square brackets that surround the +command. The \fInumComponents\fR field is always 0 (the nested command +is not parsed; call \fBTcl_ParseCommand\fR recursively if you want to +see its tokens). +.TP +\fBTCL_TOKEN_VARIABLE\fR +. +The token describes a variable substitution, including the +\fB$\fR, variable name, and array index (if there is one) up through the +close parenthesis that terminates the index. This token is followed +by one or more additional tokens that describe the variable name and +array index. If \fInumComponents\fR is 1 then the variable is a +scalar and the next token is a \fBTCL_TOKEN_TEXT\fR token that gives the +variable name. If \fInumComponents\fR is greater than 1 then the +variable is an array: the first sub-token is a \fBTCL_TOKEN_TEXT\fR +token giving the array name and the remaining sub-tokens are +\fBTCL_TOKEN_TEXT\fR, \fBTCL_TOKEN_BS\fR, \fBTCL_TOKEN_COMMAND\fR, and +\fBTCL_TOKEN_VARIABLE\fR tokens that must be concatenated to produce the +array index. The \fInumComponents\fR field includes nested sub-tokens +that are part of \fBTCL_TOKEN_VARIABLE\fR tokens in the array index. +.TP +\fBTCL_TOKEN_SUB_EXPR\fR +. +The token describes one subexpression of an expression +(or an entire expression). +A subexpression may consist of a value +such as an integer literal, variable substitution, +or parenthesized subexpression; +it may also consist of an operator and its operands. +The token starts with the first non-blank character of the subexpression +up to but not including the space, brace, close-paren, or bracket +that terminates the subexpression. +This token is followed by one or more additional tokens +that describe the subexpression. +If the first sub-token after the \fBTCL_TOKEN_SUB_EXPR\fR token +is a \fBTCL_TOKEN_OPERATOR\fR token, +the subexpression consists of an operator and its token operands. +If the operator has no operands, the subexpression consists of +just the \fBTCL_TOKEN_OPERATOR\fR token. +Each operand is described by a \fBTCL_TOKEN_SUB_EXPR\fR token. +Otherwise, the subexpression is a value described by +one of the token types \fBTCL_TOKEN_WORD\fR, \fBTCL_TOKEN_TEXT\fR, +\fBTCL_TOKEN_BS\fR, \fBTCL_TOKEN_COMMAND\fR, +\fBTCL_TOKEN_VARIABLE\fR, and \fBTCL_TOKEN_SUB_EXPR\fR. +The \fInumComponents\fR field +counts the total number of sub-tokens that make up the subexpression; +this includes the sub-tokens for any nested \fBTCL_TOKEN_SUB_EXPR\fR tokens. +.TP +\fBTCL_TOKEN_OPERATOR\fR +. +The token describes one operator of an expression +such as \fB&&\fR or \fBhypot\fR. +A \fBTCL_TOKEN_OPERATOR\fR token is always preceded by a +\fBTCL_TOKEN_SUB_EXPR\fR token +that describes the operator and its operands; +the \fBTCL_TOKEN_SUB_EXPR\fR token's \fInumComponents\fR field +can be used to determine the number of operands. +A binary operator such as \fB*\fR +is followed by two \fBTCL_TOKEN_SUB_EXPR\fR tokens +that describe its operands. +A unary operator like \fB\-\fR +is followed by a single \fBTCL_TOKEN_SUB_EXPR\fR token +for its operand. +If the operator is a math function such as \fBlog10\fR, +the \fBTCL_TOKEN_OPERATOR\fR token will give its name and +the following \fBTCL_TOKEN_SUB_EXPR\fR tokens will describe +its operands; +if there are no operands (as with \fBrand\fR), +no \fBTCL_TOKEN_SUB_EXPR\fR tokens follow. +There is one trinary operator, \fB?\fR, +that appears in if-then-else subexpressions +such as \fIx\fB?\fIy\fB:\fIz\fR; +in this case, the \fB?\fR \fBTCL_TOKEN_OPERATOR\fR token +is followed by three \fBTCL_TOKEN_SUB_EXPR\fR tokens for the operands +\fIx\fR, \fIy\fR, and \fIz\fR. +The \fInumComponents\fR field for a \fBTCL_TOKEN_OPERATOR\fR token +is always 0. +.PP +After \fBTcl_ParseCommand\fR returns, the first token pointed to by +the \fItokenPtr\fR field of the +Tcl_Parse structure always has type \fBTCL_TOKEN_WORD\fR or +\fBTCL_TOKEN_SIMPLE_WORD\fR or \fBTCL_TOKEN_EXPAND_WORD\fR. +It is followed by the sub-tokens +that must be concatenated to produce the value of that word. +The next token is the \fBTCL_TOKEN_WORD\fR or \fBTCL_TOKEN_SIMPLE_WORD\fR +of \fBTCL_TOKEN_EXPAND_WORD\fR token for the second word, +followed by sub-tokens for that +word, and so on until all \fInumWords\fR have been accounted +for. +.PP +After \fBTcl_ParseExpr\fR returns, the first token pointed to by +the \fItokenPtr\fR field of the +Tcl_Parse structure always has type \fBTCL_TOKEN_SUB_EXPR\fR. +It is followed by the sub-tokens that must be evaluated +to produce the value of the expression. +Only the token information in the Tcl_Parse structure +is modified: the \fIcommentStart\fR, \fIcommentSize\fR, +\fIcommandStart\fR, and \fIcommandSize\fR fields are not modified +by \fBTcl_ParseExpr\fR. +.PP +After \fBTcl_ParseBraces\fR returns, +the array of tokens pointed to by the \fItokenPtr\fR field of the +Tcl_Parse structure will contain a single \fBTCL_TOKEN_TEXT\fR token +if the braced string does not contain any backslash-newlines. +If the string does contain backslash-newlines, +the array of tokens will contain one or more +\fBTCL_TOKEN_TEXT\fR or \fBTCL_TOKEN_BS\fR sub-tokens +that must be concatenated to produce the value of the string. +If the braced string was just \fB{}\fR +(that is, the string was empty), +the single \fBTCL_TOKEN_TEXT\fR token will have a \fIsize\fR field +containing zero; +this ensures that at least one token appears +to describe the braced string. +Only the token information in the Tcl_Parse structure +is modified: the \fIcommentStart\fR, \fIcommentSize\fR, +\fIcommandStart\fR, and \fIcommandSize\fR fields are not modified +by \fBTcl_ParseBraces\fR. +.PP +After \fBTcl_ParseQuotedString\fR returns, +the array of tokens pointed to by the \fItokenPtr\fR field of the +Tcl_Parse structure depends on the contents of the quoted string. +It will consist of one or more \fBTCL_TOKEN_TEXT\fR, \fBTCL_TOKEN_BS\fR, +\fBTCL_TOKEN_COMMAND\fR, and \fBTCL_TOKEN_VARIABLE\fR sub-tokens. +The array always contains at least one token; +for example, if the argument \fIstart\fR is empty, +the array returned consists of a single \fBTCL_TOKEN_TEXT\fR token +with a zero \fIsize\fR field. +Only the token information in the Tcl_Parse structure +is modified: the \fIcommentStart\fR, \fIcommentSize\fR, +\fIcommandStart\fR, and \fIcommandSize\fR fields are not modified. +.PP +After \fBTcl_ParseVarName\fR returns, the first token pointed to by +the \fItokenPtr\fR field of the +Tcl_Parse structure always has type \fBTCL_TOKEN_VARIABLE\fR. It +is followed by the sub-tokens that make up the variable name as +described above. The total length of the variable name is +contained in the \fIsize\fR field of the first token. +As in \fBTcl_ParseExpr\fR, +only the token information in the Tcl_Parse structure +is modified by \fBTcl_ParseVarName\fR: +the \fIcommentStart\fR, \fIcommentSize\fR, +\fIcommandStart\fR, and \fIcommandSize\fR fields are not modified. +.PP +All of the character pointers in the +Tcl_Parse and Tcl_Token structures refer +to characters in the \fIstart\fR argument passed to +\fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, +\fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR. +.PP +There are additional fields in the Tcl_Parse structure after the +\fInumTokens\fR field, but these are for the private use of +\fBTcl_ParseCommand\fR, \fBTcl_ParseExpr\fR, \fBTcl_ParseBraces\fR, +\fBTcl_ParseQuotedString\fR, and \fBTcl_ParseVarName\fR; they should not be +referenced by code outside of these procedures. +.SH KEYWORDS +backslash substitution, braces, command, expression, parse, token, variable substitution |