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Tk_ParseArgv(3) Tk Library Procedures Tk_ParseArgv(3)
____________________________________________________________________________________________________________
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.
____________________________________________________________________________________________________________
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[_] 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[_] 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 interp->result 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 {
char *key;
int type;
char *src;
char *dst;
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 addi-tional additional
tional 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 argu-ment argument
ment 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 argu-ments arguments
ments 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 argu-ment argument
ment 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 argu-ments arguments
ments 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 for-mat format
mat a message describing all the valid arguments. The message is placed in interp->result and
Tk_ParseArgv returns TCL_ERROR. When this happens, the caller normally prints the help mes-sage message
sage 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 documenta-tion, documentation,
tion, 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 proce-dure, procedure,
dure, 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 interp->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[_] 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[_] 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[_], 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, (char *) NULL, (char *) &numReps,
"Number of repetitions"},
{"-of", TK_ARGV_STRING, (char *) NULL, (char *) &fileName,
"Name of file for output"},
{"x", TK_ARGV_REST, (char *) NULL, (char *) &exec,
"File to exec, followed by any arguments (must be last argument)."},
{(char *) NULL, TK_ARGV_END, (char *) NULL, (char *) NULL,
(char *) NULL}
};
main(argc, argv)
int argc;
char *argv[];
{
...
if (Tk_ParseArgv(interp, tkwin, &argc, argv, argTable, 0) != TCL_OK) {
fprintf(stderr, "%s\n", interp->result);
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)
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