Tk_ParseArgv(3) Tk Library Procedures Tk_ParseArgv(3)

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NAME

Tk_ParseArgv - process command-line options

SYNOPSIS

#include <tk.h>

int
Tk_ParseArgv(interp, tkwin, argcPtr, argv, argTable, flags)

ARGUMENTS

Tcl_Interp *interp (in) Interpreter to use for returning
error messages.

Tk_Window tkwin (in) Window to use when arguments
specify Tk options. If NULL,
then no Tk options will be
processed.

int argcPtr (in/out) Pointer to number of arguments in
argv; gets modified to hold
number of unprocessed arguments
that remain after the call.

const char **argv (in/out) Command line arguments passed to
main program. Modified to hold
unprocessed arguments that remain
after the call.

Tk_ArgvInfo *argTable (in) Array of argument descriptors,
terminated by element with type
TK_ARGV_END.

int flags (in) If non-zero, then it specifies
one or more flags that control
the parsing of arguments.
Different flags may be OR'ed
together. The flags currently
defined are
TK_ARGV_DONT_SKIP_FIRST_ARG,
TK_ARGV_NO_ABBREV,
TK_ARGV_NO_LEFTOVERS, and
TK_ARGV_NO_DEFAULTS.
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DESCRIPTION

Tk_ParseArgv processes an array of command-line arguments according
to a table describing the kinds of arguments that are expected. Each
of the arguments in argv is processed in turn: if it matches one of
the entries in argTable, the argument is processed according to that
entry and discarded. The arguments that do not match anything in
argTable are copied down to the beginning of argv (retaining their
original order) and returned to the caller. At the end of the call
Tk_ParseArgv sets *argcPtr to hold the number of arguments that are
left in argv, and argv[*argcPtr] will hold the value NULL. Normally,
Tk_ParseArgv assumes that argv[0] is a command name, so it is treated
like an argument that does not match argTable and returned to the
caller; however, if the TK_ARGV_DONT_SKIP_FIRST_ARG bit is set in
flags then argv[0] will be processed just like the other elements of
argv.

Tk_ParseArgv normally returns the value TCL_OK. If an error occurs
while parsing the arguments, then TCL_ERROR is returned and
Tk_ParseArgv will leave an error message in the result of interpreter
interp in the standard Tcl fashion. In the event of an error return,
*argvPtr will not have been modified, but argv could have been
partially modified. The possible causes of errors are explained
below.

The argTable array specifies the kinds of arguments that are
expected; each of its entries has the following structure:
typedef struct {
const char *key;
int type;
char *src;
char *dst;
const char *help;
} Tk_ArgvInfo;
The key field is a string such as "-display" or "-bg" that is
compared with the values in argv. Type indicates how to process an
argument that matches key (more on this below). Src and dst are
additional values used in processing the argument. Their exact usage
depends on type, but typically src indicates a value and dst
indicates where to store the value. The char * declarations for src
and dst are placeholders: the actual types may be different.
Lastly, help is a string giving a brief description of this option;
this string is printed when users ask for help about command-line
options.

When processing an argument in argv, Tk_ParseArgv compares the
argument to each of the key's in argTable. Tk_ParseArgv selects the
first specifier whose key matches the argument exactly, if such a
specifier exists. Otherwise Tk_ParseArgv selects a specifier for
which the argument is a unique abbreviation. If the argument is a
unique abbreviation for more than one specifier, then an error is
returned. If there is no matching entry in argTable, then the
argument is skipped and returned to the caller.

Once a matching argument specifier is found, Tk_ParseArgv processes
the argument according to the type field of the specifier. The
argument that matched key is called "the matching argument" in the
descriptions below. As part of the processing, Tk_ParseArgv may also
use the next argument in argv after the matching argument, which is
called "the following argument". The legal values for type, and the
processing that they cause, are as follows:

TK_ARGV_END
Marks the end of the table. The last entry in argTable must
have this type; all of its other fields are ignored and it
will never match any arguments.

TK_ARGV_CONSTANT
Src is treated as an integer and dst is treated as a pointer
to an integer. Src is stored at *dst. The matching argument
is discarded.

TK_ARGV_INT
The following argument must contain an integer string in the
format accepted by strtol (e.g. "0" and "0x" prefixes may be
used to specify octal or hexadecimal numbers, respectively).
Dst is treated as a pointer to an integer; the following
argument is converted to an integer value and stored at *dst.
Src is ignored. The matching and following arguments are
discarded from argv.

TK_ARGV_FLOAT
The following argument must contain a floating-point number in
the format accepted by strtol. Dst is treated as the address
of a double-precision floating point value; the following
argument is converted to a double-precision value and stored
at *dst. The matching and following arguments are discarded
from argv.

TK_ARGV_STRING
In this form, dst is treated as a pointer to a (char *);
Tk_ParseArgv stores at *dst a pointer to the following
argument, and discards the matching and following arguments
from argv. Src is ignored.

TK_ARGV_UID
This form is similar to TK_ARGV_STRING, except that the
argument is turned into a Tk_Uid by calling Tk_GetUid. Dst is
treated as a pointer to a Tk_Uid; Tk_ParseArgv stores at *dst
the Tk_Uid corresponding to the following argument, and
discards the matching and following arguments from argv. Src
is ignored.

TK_ARGV_CONST_OPTION
This form causes a Tk option to be set (as if the option
command had been invoked). The src field is treated as a
pointer to a string giving the value of an option, and dst is
treated as a pointer to the name of the option. The matching
argument is discarded. If tkwin is NULL, then argument
specifiers of this type are ignored (as if they did not
exist).

TK_ARGV_OPTION_VALUE
This form is similar to TK_ARGV_CONST_OPTION, except that the
value of the option is taken from the following argument
instead of from src. Dst is used as the name of the option.
Src is ignored. The matching and following arguments are
discarded. If tkwin is NULL, then argument specifiers of this
type are ignored (as if they did not exist).

TK_ARGV_OPTION_NAME_VALUE
In this case the following argument is taken as the name of a
Tk option and the argument after that is taken as the value
for that option. Both src and dst are ignored. All three
arguments are discarded from argv. If tkwin is NULL, then
argument specifiers of this type are ignored (as if they did
not exist).

TK_ARGV_HELP
When this kind of option is encountered, Tk_ParseArgv uses the
help fields of argTable to format a message describing all the
valid arguments. The message is placed in interpreter
interp's result and Tk_ParseArgv returns TCL_ERROR. When this
happens, the caller normally prints the help message and
aborts. If the key field of a TK_ARGV_HELP specifier is NULL,
then the specifier will never match any arguments; in this
case the specifier simply provides extra documentation, which
will be included when some other TK_ARGV_HELP entry causes
help information to be returned.

TK_ARGV_REST
This option is used by programs or commands that allow the
last several of their options to be the name and/or options
for some other program. If a TK_ARGV_REST argument is found,
then Tk_ParseArgv does not process any of the remaining
arguments; it returns them all at the beginning of argv
(along with any other unprocessed arguments). In addition,
Tk_ParseArgv treats dst as the address of an integer value,
and stores at *dst the index of the first of the TK_ARGV_REST
options in the returned argv. This allows the program to
distinguish the TK_ARGV_REST options from other unprocessed
options that preceded the TK_ARGV_REST.

TK_ARGV_FUNC
For this kind of argument, src is treated as the address of a
procedure, which is invoked to process the following argument.
The procedure should have the following structure:
int
func(dst, key, nextArg)
char *dst;
char *key;
char *nextArg;
{
}
The dst and key parameters will contain the corresponding
fields from the argTable entry, and nextArg will point to the
following argument from argv (or NULL if there are not any
more arguments left in argv). If func uses nextArg (so that
Tk_ParseArgv should discard it), then it should return 1.
Otherwise it should return 0 and TkParseArgv will process the
following argument in the normal fashion. In either event the
matching argument is discarded.

TK_ARGV_GENFUNC
This form provides a more general procedural escape. It
treats src as the address of a procedure, and passes that
procedure all of the remaining arguments. The procedure
should have the following form:
int
genfunc(dst, interp, key, argc, argv)
char *dst;
Tcl_Interp *interp;
char *key;
int argc;
char **argv;
{
}
The dst and key parameters will contain the corresponding
fields from the argTable entry. Interp will be the same as
the interp argument to Tcl_ParseArgv. Argc and argv refer to
all of the options after the matching one. Genfunc should
behave in a fashion similar to Tk_ParseArgv: parse as many of
the remaining arguments as it can, then return any that are
left by compacting them to the beginning of argv (starting at
argv[0]). Genfunc should return a count of how many arguments
are left in argv; Tk_ParseArgv will process them. If genfunc
encounters an error then it should leave an error message in
interpreter interp's result, in the usual Tcl fashion, and
return -1; when this happens Tk_ParseArgv will abort its
processing and return TCL_ERROR.

FLAGS

TK_ARGV_DONT_SKIP_FIRST_ARG
Tk_ParseArgv normally treats argv[0] as a program or command
name, and returns it to the caller just as if it had not
matched argTable. If this flag is given, then argv[0] is not
given special treatment.

TK_ARGV_NO_ABBREV
Normally, Tk_ParseArgv accepts unique abbreviations for key
values in argTable. If this flag is given then only exact
matches will be acceptable.

TK_ARGV_NO_LEFTOVERS
Normally, Tk_ParseArgv returns unrecognized arguments to the
caller. If this bit is set in flags then Tk_ParseArgv will
return an error if it encounters any argument that does not
match argTable. The only exception to this rule is argv[0],
which will be returned to the caller with no errors as long as
TK_ARGV_DONT_SKIP_FIRST_ARG is not specified.

TK_ARGV_NO_DEFAULTS
Normally, Tk_ParseArgv searches an internal table of standard
argument specifiers in addition to argTable. If this bit is
set in flags, then Tk_ParseArgv will use only argTable and not
its default table.

EXAMPLE

Here is an example definition of an argTable and some sample command
lines that use the options. Note the effect on argc and argv;
arguments processed by Tk_ParseArgv are eliminated from argv, and
argc is updated to reflect reduced number of arguments.
/*
* Define and set default values for globals.
*/
int debugFlag = 0;
int numReps = 100;
char defaultFileName[] = "out";
char *fileName = defaultFileName;
Boolean exec = FALSE;

/*
* Define option descriptions.
*/
Tk_ArgvInfo argTable[] = {
{"-X", TK_ARGV_CONSTANT, (char *) 1, (char *) &debugFlag,
"Turn on debugging printfs"},
{"-N", TK_ARGV_INT, NULL, (char *) &numReps,
"Number of repetitions"},
{"-of", TK_ARGV_STRING, NULL, (char *) &fileName,
"Name of file for output"},
{"x", TK_ARGV_REST, NULL, (char *) &exec,
"File to exec, followed by any arguments (must be last argument)."},
{NULL, TK_ARGV_END, NULL, NULL,
NULL}
};

main(argc, argv)
int argc;
char *argv[];
{
...

if (Tk_ParseArgv(interp, tkwin, &argc, argv, argTable, 0) != TCL_OK) {
fprintf(stderr, "%s\n", Tcl_GetString(Tcl_GetObjResult(interp)));
exit(1);
}

/*
* Remainder of the program.
*/
}

Note that default values can be assigned to variables named in
argTable: the variables will only be overwritten if the particular
arguments are present in argv. Here are some example command lines
and their effects.
prog -N 200 infile # just sets the numReps variable to 200
prog -of out200 infile # sets fileName to reference "out200"
prog -XN 10 infile # sets the debug flag, also sets numReps
In all of the above examples, argc will be set by Tk_ParseArgv to 2,
argv[0] will be "prog", argv[1] will be "infile", and argv[2] will be
NULL.

KEYWORDS

arguments, command line, options

Tk Tk_ParseArgv(3)