path: root/doc/ParseArgs.3

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.TH Tcl_ParseArgsObjv 3 8.6 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_ParseArgsObjv \- parse arguments according to a tabular description
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
int
\fBTcl_ParseArgsObjv\fR(\fIinterp, argTable, objcPtr, objv, remObjv\fR)
.SH ARGUMENTS
.AS "const Tcl_ArgvInfo" ***remObjv in/out
.AP Tcl_Interp *interp out
Where to store error messages.
.AP "const Tcl_ArgvInfo" *argTable in
Pointer to array of option descriptors.
.AP int *objcPtr in/out
A pointer to variable holding number of arguments in \fIobjv\fR. Will be
modified to hold number of arguments left in the unprocessed argument list
stored in \fIremObjv\fR.
.AP "Tcl_Obj *const" *objv in
The array of arguments to be parsed.
.AP Tcl_Obj ***remObjv out
Pointer to a variable that will hold the array of unprocessed arguments.
Should be NULL if no return of unprocessed arguments is required. If
\fIobjcPtr\fR is updated to a non-zero value, the array returned through this
must be deallocated using \fBckfree\fR.
.BE
.SH DESCRIPTION
.PP
The \fBTcl_ParseArgsObjv\fR function provides a system for parsing argument
lists of the form
.QW "\fB\-someName \fIsomeValue\fR ..." .
Such argument lists are commonly found both in the arguments to a program and
in the arguments to an individual Tcl command. This parser assumes that the
order of the arguments does not matter, other than in so far as later copies
of a duplicated option overriding earlier ones.
.PP
The argument array is described by the \fIobjcPtr\fR and \fIobjv\fR
parameters, and an array of unprocessed arguments is returned through the
\fIobjcPtr\fR and \fIremObjv\fR parameters; if no return of unprocessed
arguments is desired, the \fIremObjv\fR parameter should be NULL. If any
problems happen, including if the
.QW "generate help"
option is selected, an error message is left in the interpreter result and
TCL_ERROR is returned. Otherwise, the interpreter result is left unchanged and
TCL_OK is returned.
.PP
The collection of arguments to be parsed is described by the \fIargTable\fR
parameter. This points to a table of descriptor structures that is terminated
by an entry with the \fItype\fR field set to TCL_ARGV_END. As convenience, the
following prototypical entries are provided:
.TP
\fBTCL_ARGV_AUTO_HELP\fR
.
Enables the argument processor to provide help when passed the argument
.QW \fB\-help\fR .
.TP
\fBTCL_ARGV_AUTO_REST\fR
.
Instructs the argument processor that arguments after
.QW \fB\-\-\fR
are to be unprocessed.
.TP
\fBTCL_ARGV_TABLE_END\fR
.
Marks the end of the table of argument descriptors.
.SS "ARGUMENT DESCRIPTOR ENTRIES"
.PP
Each entry of the argument descriptor table must be a structure of type
\fBTcl_ArgvInfo\fR. The structure is defined as this:
.PP
.CS
typedef struct {
    int \fItype\fR;
    const char *\fIkeyStr\fR;
    void *\fIsrcPtr\fR;
    void *\fIdstPtr\fR;
    const char *\fIhelpStr\fR;
    ClientData \fIclientData\fR;
} \fBTcl_ArgvInfo\fR;
.CE
.PP
The \fIkeyStr\fR field contains the name of the option; by convention, this
will normally begin with a
.QW \fB\-\fR
character. The \fItype\fR, \fIsrcPtr\fR, \fIdstPtr\fR and \fIclientData\fR
fields describe the interpretation of the value of the argument, as described
below. The \fIhelpStr\fR field gives some text that is used to provide help to
users when they request it.
.PP
As noted above, the \fItype\fR field is used to describe the interpretation of
the argument's value. The following values are acceptable values for
\fItype\fR:
.TP
\fBTCL_ARGV_CONSTANT\fR
.
The argument does not take any following value argument. If this argument is
present, the int pointed to by the \fIsrcPtr\fR field is copied to the
\fIdstPtr\fR field. The \fIclientData\fR field is ignored.
.TP
\fBTCL_ARGV_END\fR
.
This value marks the end of all option descriptors in the table. All other
fields are ignored.
.TP
\fBTCL_ARGV_FLOAT\fR
.
This argument takes a following floating point value argument. The value (once
parsed by \fBTcl_GetDoubleFromObj\fR) will be stored as a double-precision
value in the variable pointed to by the \fIdstPtr\fR field. The \fIsrcPtr\fR
and \fIclientData\fR fields are ignored.
.TP
\fBTCL_ARGV_FUNC\fR
.
This argument optionally takes a following value argument; it is up to the
handler callback function passed in \fIsrcPtr\fR to decide. That function will
have the following signature:
.RS
.PP
.CS
typedef int (\fBTcl_ArgvFuncProc\fR)(
        ClientData \fIclientData\fR,
        Tcl_Obj *\fIobjPtr\fR,
        void *\fIdstPtr\fR);
.CE
.PP
The result is a boolean value indicating whether to consume the following
argument. The \fIclientData\fR is the value from the table entry, the
\fIobjPtr\fR is the value that represents the following argument or NULL if
there are no following arguments at all, and the \fIdstPtr\fR argument to the
\fBTcl_ArgvFuncProc\fR is the location to write the parsed value to.
.RE
.TP
\fBTCL_ARGV_GENFUNC\fR
.
This argument takes zero or more following arguments; the handler callback
function passed in \fIsrcPtr\fR returns how many (or a negative number to
signal an error, in which case it should also set the interpreter result). The
function will have the following signature:
.RS
.PP
.CS
typedef int (\fBTcl_ArgvGenFuncProc\fR)(
        ClientData \fIclientData\fR,
        Tcl_Interp *\fIinterp\fR,
        int \fIobjc\fR,
        Tcl_Obj *const *\fIobjv\fR,
        void *\fIdstPtr\fR);
.CE
.PP
The \fIclientData\fR is the value from the table entry, the \fIinterp\fR is
where to store any error messages, the \fIkeyStr\fR is the name of the
argument, \fIobjc\fR and \fIobjv\fR describe an array of all the remaining
arguments, and \fIdstPtr\fR argument to the \fBTcl_ArgvGenFuncProc\fR is the
location to write the parsed value (or values) to.
.RE
.TP
\fBTCL_ARGV_HELP\fR
.
This special argument does not take any following value argument, but instead
causes \fBTcl_ParseArgsObjv\fR to generate an error message describing the
arguments supported. All other fields except the \fIhelpStr\fR field are
ignored.
.TP
\fBTCL_ARGV_INT\fR
.
This argument takes a following integer value argument. The value (once parsed
by \fBTcl_GetIntFromObj\fR) will be stored as an int in the variable pointed
to by the \fIdstPtr\fR field. The \fIsrcPtr\fR field is ignored.
.TP
\fBTCL_ARGV_REST\fR
.
This special argument does not take any following value argument, but instead
marks all following arguments to be left unprocessed. The \fIsrcPtr\fR,
\fIdstPtr\fR and \fIclientData\fR fields are ignored.
.TP
\fBTCL_ARGV_STRING\fR
.
This argument takes a following string value argument. A pointer to the string
will be stored at \fIdstPtr\fR; the string inside will have a lifetime linked
to the lifetime of the string representation of the argument value that it
came from, and so should be copied if it needs to be retained. The
\fIsrcPtr\fR and \fIclientData\fR fields are ignored.
.SH "SEE ALSO"
Tcl_GetIndexFromObj(3), Tcl_Main(3), Tcl_CreateObjCommand(3)
.SH KEYWORDS
argument, parse
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