Tribblix: manual page: popt.3

POPT(3) Linux Programmer's Manual POPT(3)

NAME

popt - Parse command line options

SYNOPSIS

#include <popt.h>

poptContext poptGetContext(const char * name, int argc,
const char ** argv,
const struct poptOption * options,
unsigned int flags);

void poptFreeContext(poptContext con);

void poptResetContext(poptContext con);

int poptGetNextOpt(poptContext con);

const char * poptGetOptArg(poptContext con);

const char * poptGetArg(poptContext con);

const char * poptPeekArg(poptContext con);

const char ** poptGetArgs(poptContext con);

const char *const poptStrerror(const int error);

const char * poptBadOption(poptContext con, int flags);

int poptReadDefaultConfig(poptContext con, int flags);

int poptReadConfigFile(poptContext con, char * fn);

int poptAddAlias(poptContext con, struct poptAlias alias,
int flags);

int poptParseArgvString(char * s, int * argcPtr,
const char *** argvPtr);

int poptDupArgv(int argc, const char ** argv, int * argcPtr,
const char *** argvPtr);

int poptStuffArgs(poptContext con, const char ** argv);

DESCRIPTION

The popt library exists essentially for parsing command-line options.
It is found superior in many ways when compared to parsing the argv
array by hand or using the getopt functions getopt() and
getopt_long() [see getopt(3)]. Some specific advantages of popt are:
it does not utilize global variables, thus enabling multiple passes
in parsing argv ; it can parse an arbitrary array of argv-style
elements, allowing parsing of command-line-strings from any source;
it provides a standard method of option aliasing (to be discussed at
length below.); it can exec external option filters; and, finally, it
can automatically generate help and usage messages for the
application.

Like getopt_long(), the popt library supports short and long style
options. Recall that a short option consists of a - character
followed by a single alphanumeric character. A long option, common
in GNU utilities, consists of two - characters followed by a string
made up of letters, numbers and hyphens. Long options are optionally
allowed to begin with a single -, primarily to allow command-line
compatibility between popt applications and X toolkit applications.
Either type of option may be followed by an argument. A space
separates a short option from its arguments; either a space or an =
separates a long option from an argument.

The popt library is highly portable and should work on any POSIX
platform. The latest version is distributed with rpm and is always
available from: ftp://ftp.rpm.org/pub/rpm/dist.

It may be redistributed under the X consortium license, see the file
COPYING in the popt source distribution for details.

BASIC POPT USAGE

1. THE OPTION TABLE
Applications provide popt with information on their command-line
options by means of an "option table," i.e., an array of struct
poptOption structures:

#include <popt.h>

struct poptOption {
const char * longName; /* may be NULL */
char shortName; /* may be '\0' */
unsigned int argInfo; /* type of argument expected after the option */
void * arg; /* depends on argInfo */
int val; /* 0 means don't return, just update arg */
const char * descrip; /* description for autohelp -- may be NULL */
const char * argDescrip; /* argument description for autohelp -- may be NULL*/
};

Each member of the table defines a single option that may be passed
to the program. Long and short options are considered a single
option that may occur in two different forms. The first two members,
longName and shortName, define the names of the option; the first is
a long name, while the latter is a single character.

The argInfo member tells popt what type of argument is expected after
the option. If no argument is expected, POPT_ARG_NONE should be
used. The valid values of argInfo are shown in the following table:

Value Description arg Type
POPT_ARG_NONE No argument expected int
POPT_ARG_STRING No type checking to be performed char *
POPT_ARG_ARGV No type checking to be performed char **
POPT_ARG_SHORT A short argument is expected short
POPT_ARG_INT An integer argument is expected int
POPT_ARG_LONG A long integer is expected long
POPT_ARG_LONGLONG A long long integer is expected long long
POPT_ARG_VAL Integer value taken from val int
POPT_ARG_FLOAT A float argument is expected float
POPT_ARG_DOUBLE A double argument is expected double

For numeric values, if the argInfo value is bitwise or'd with one of
POPT_ARGFLAG_OR, POPT_ARGFLAG_AND, or POPT_ARGFLAG_XOR, the value is
saved by performing an OR, AND, or XOR. If the argInfo value is
bitwise or'd with POPT_ARGFLAG_NOT, the value will be negated before
saving. For the common operations of setting and/or clearing bits,
POPT_BIT_SET and POPT_BIT_CLR have the appropriate flags set to
perform bit operations.

If the argInfo value is bitwise or'd with POPT_ARGFLAG_ONEDASH, the
long argument may be given with a single - instead of two. For
example, if --longopt is an option with POPT_ARGFLAG_ONEDASH, is
specified, -longopt is accepted as well.

The next element, arg, allows popt to automatically update program
variables when the option is used. If arg is NULL, it is ignored and
popt takes no special action. Otherwise it should point to a
variable of the type indicated in the right-most column of the table
above. A POPT_ARG_ARGV arg will (re-)allocate an array of char *
string pointers, append the string argument, and add a NULL sentinel
at the end of the array as needed. The target char ** address of a
POPT_ARG_ARGV arg should be initialized to NULL.

If the option takes no argument (argInfo is POPT_ARG_NONE), the
variable pointed to by arg is set to 1 when the option is used.
(Incidentally, it will perhaps not escape the attention of hunt-and-
peck typists that the value of POPT_ARG_NONE is 0.) If the option
does take an argument, the variable that arg points to is updated to
reflect the value of the argument. Any string is acceptable for
POPT_ARG_STRING and POPT_ARG_ARGV arguments, but POPT_ARG_INT,
POPT_ARG_SHORT, POPT_ARG_LONG, POPT_ARG_LONGLONG, POPT_ARG_FLOAT, and
POPT_ARG_DOUBLE are converted to the appropriate type, and an error
returned if the conversion fails.

POPT_ARG_VAL causes arg to be set to the (integer) value of val when
the argument is found. This is most often useful for mutually-
exclusive arguments in cases where it is not an error for multiple
arguments to occur and where you want the last argument specified to
win; for example, "rm -i -f". POPT_ARG_VAL causes the parsing
function not to return a value, since the value of val has already
been used.

If the argInfo value is bitwise or'd with POPT_ARGFLAG_OPTIONAL, the
argument to the long option may be omitted. If the long option is
used without an argument, a default value of zero or NULL will be
saved (if the arg pointer is present), otherwise behavior will be
identical to a long option with argument.

The next option, val, is the value popt's parsing function should
return when the option is encountered. If it is 0, the parsing
function does not return a value, instead parsing the next command-
line argument.

The last two options, descrip and argDescrip are only required if
automatic help messages are desired (automatic usage messages can be
generated without them). descrip is a text description of the
argument and argDescrip is a short summary of the type of arguments
the option expects, or NULL if the option doesn't require any
arguments.

If popt should automatically provide --usage and --help (-?) options,
one line in the table should be the macro POPT_AUTOHELP. This macro
includes another option table (via POPT_ARG_INCLUDE_TABLE ; see
below) in the main one which provides the table entries for these
arguments. When --usage or --help are passed to programs which use
popt's automatic help, popt displays the appropriate message on
stderr as soon as it finds the option, and exits the program with a
return code of 0. If you want to use popt's automatic help generation
in a different way, you need to explicitly add the option entries to
your programs option table instead of using POPT_AUTOHELP.

If the argInfo value is bitwise or'd with POPT_ARGFLAG_DOC_HIDDEN,
the argument will not be shown in help output.

If the argInfo value is bitwise or'd with POPT_ARGFLAG_SHOW_DEFAULT,
the initial value of the arg will be shown in help output.

The final structure in the table should have all the pointer values
set to NULL and all the arithmetic values set to 0, marking the end
of the table. The macro POPT_TABLEEND is provided to do that.

There are two types of option table entries which do not specify
command line options. When either of these types of entries are used,
the longName element must be NULL and the shortName element must be
'\0'.

The first of these special entry types allows the application to nest
another option table in the current one; such nesting may extend
quite deeply (the actual depth is limited by the program's stack).
Including other option tables allows a library to provide a standard
set of command-line options to every program which uses it (this is
often done in graphical programming toolkits, for example). To do
this, set the argInfo field to POPT_ARG_INCLUDE_TABLE and the arg
field to point to the table which is being included. If automatic
help generation is being used, the descrip field should contain an
overall description of the option table being included.

The other special option table entry type tells popt to call a
function (a callback) when any option in that table is found. This is
especially useful when included option tables are being used, as the
program which provides the top-level option table doesn't need to be
aware of the other options which are provided by the included table.
When a callback is set for a table, the parsing function never
returns information on an option in the table. Instead, options
information must be retained via the callback or by having popt set a
variable through the option's arg field. Option callbacks should
match the following prototype:

void poptCallbackType(poptContext con,
const struct poptOption * opt,
const char * arg, void * data);

The first parameter is the context which is being parsed (see the
next section for information on contexts), opt points to the option
which triggered this callback, and arg is the option's argument. If
the option does not take an argument, arg is NULL. The final
parameter, data is taken from the descrip field of the option table
entry which defined the callback. As descrip is a pointer, this
allows callback functions to be passed an arbitrary set of data
(though a typecast will have to be used).

The option table entry which defines a callback has an argInfo of
POPT_ARG_CALLBACK, an arg which points to the callback function, and
a descrip field which specifies an arbitrary pointer to be passed to
the callback.

2. CREATING A CONTEXT
popt can interleave the parsing of multiple command-line sets. It
allows this by keeping all the state information for a particular set
of command-line arguments in a poptContext data structure, an opaque
type that should not be modified outside the popt library.

New popt contexts are created by poptGetContext():

poptContext poptGetContext(const char * name, int argc,
const char ** argv,
const struct poptOption * options,
unsigned int flags);

The first parameter, name, is used only for alias handling (discussed
later). It should be the name of the application whose options are
being parsed, or should be NULL if no option aliasing is desired. The
next two arguments specify the command-line arguments to parse.
These are generally passed to poptGetContext() exactly as they were
passed to the program's main() function. The options parameter
points to the table of command-line options, which was described in
the previous section. The final parameter, flags, can be any bitwise
or combination of the following four values:

Value Description
POPT_CONTEXT_NO_EXEC Ignore exec expansions
POPT_CONTEXT_KEEP_FIRST Do not ignore argv[0]
POPT_CONTEXT_POSIXMEHARDER Options cannot follow arguments
POPT_CONTEXT_ARG_OPTS Return the arguments as options of value 0

A poptContext keeps track of which options have already been parsed
and which remain, among other things. If a program wishes to restart
option processing of a set of arguments, it can reset the poptContext
by passing the context as the sole argument to poptResetContext().

When argument processing is complete, the process should free the
poptContext as it contains dynamically allocated components. The
poptFreeContext() function takes a poptContext as its sole argument
and frees the resources the context is using.

Here are the prototypes of both poptResetContext() and
poptFreeContext():

#include <popt.h>
void poptFreeContext(poptContext con);
void poptResetContext(poptContext con);

3. PARSING THE COMMAND LINE
After an application has created a poptContext, it may begin parsing
arguments. poptGetNextOpt() performs the actual argument parsing.

#include <popt.h>
int poptGetNextOpt(poptContext con);

Taking the context as its sole argument, this function parses the
next command-line argument found. After finding the next argument in
the option table, the function fills in the object pointed to by the
option table entry's arg pointer if it is not NULL. If the val entry
for the option is non-0, the function then returns that value.
Otherwise, poptGetNextOpt() continues on to the next argument.

poptGetNextOpt() returns -1 when the final argument has been parsed,
and other negative values when errors occur. This makes it a good
idea to keep the val elements in the options table greater than 0.

If all of the command-line options are handled through arg pointers,
command-line parsing is reduced to the following line of code:

rc = poptGetNextOpt(poptcon);

Many applications require more complex command-line parsing than
this, however, and use the following structure:

while ((rc = poptGetNextOpt(poptcon)) > 0) {
switch (rc) {
/* specific arguments are handled here */
}
}

When returned options are handled, the application needs to know the
value of any arguments that were specified after the option. There
are two ways to discover them. One is to ask popt to fill in a
variable with the value of the option through the option table's arg
elements. The other is to use poptGetOptArg():

#include <popt.h>
char * poptGetOptArg(poptContext con);

This function returns the argument given for the final option
returned by poptGetNextOpt(), or it returns NULL if no argument was
specified. The calling function is responsible for deallocating this
string.

4. LEFTOVER ARGUMENTS
Many applications take an arbitrary number of command-line arguments,
such as a list of file names. When popt encounters an argument that
does not begin with a -, it assumes it is such an argument and adds
it to a list of leftover arguments. Three functions allow
applications to access such arguments:

const char * poptGetArg(poptContext con);
This function returns the next leftover argument and marks it
as processed.

const char * poptPeekArg(poptContext con);
The next leftover argument is returned but not marked as
processed. This allows an application to look ahead into the
argument list, without modifying the list.

const char ** poptGetArgs(poptContext con);
All the leftover arguments are returned in a manner identical
to argv. The final element in the returned array points to
NULL, indicating the end of the arguments.

5. AUTOMATIC HELP MESSAGES
The popt library can automatically generate help messages which
describe the options a program accepts. There are two types of help
messages which can be generated. Usage messages are a short messages
which lists valid options, but does not describe them. Help messages
describe each option on one (or more) lines, resulting in a longer,
but more useful, message. Whenever automatic help messages are used,
the descrip and argDescrip fields struct poptOption members should be
filled in for each option.

The POPT_AUTOHELP macro makes it easy to add --usage and --help
messages to your program, and is described in part 1 of this man
page. If more control is needed over your help messages, the
following two functions are available:

#include <popt.h>
void poptPrintHelp(poptContext con, FILE * f, int flags);
void poptPrintUsage(poptContext con, FILE * f, int flags);

poptPrintHelp() displays the standard help message to the stdio file
descriptor f, while poptPrintUsage() displays the shorter usage
message. Both functions currently ignore the flags argument; it is
there to allow future changes.

ERROR HANDLING

All of the popt functions that can return errors return integers.
When an error occurs, a negative error code is returned. The
following table summarizes the error codes that occur:

Error Description
POPT_ERROR_NOARG Argument missing for an option.
POPT_ERROR_BADOPT Option's argument couldn't be parsed.
POPT_ERROR_UNWANTEDARG Option does not take an argument.
POPT_ERROR_OPTSTOODEEP Option aliasing nested too deeply.
POPT_ERROR_BADQUOTE Quotations do not match.
POPT_ERROR_ERRNO errno set, use strerror(errno).
POPT_ERROR_BADNUMBER Option couldn't be converted to number.
POPT_ERROR_OVERFLOW A given number was too big or small.
POPT_ERROR_BADOPERATION Mutually exclusive logical operations requested.
POPT_ERROR_NULLARG opt->arg should not be NULL.
POPT_ERROR_MALLOC Memory allocation failed.
POPT_ERROR_BADCONFIG Config file failed sanity test.

Here is a more detailed discussion of each error:

POPT_ERROR_NOARG
An option that requires an argument was specified on the
command line, but no argument was given. This can be returned
only by poptGetNextOpt().

POPT_ERROR_BADOPT
An option was specified in argv but is not in the option
table. This error can be returned only from poptGetNextOpt().

POPT_ERROR_OPTSTOODEEP
A set of option aliases is nested too deeply. Currently, popt
follows options only 10 levels (POPT_OPTION_DEPTH) to prevent
infinite recursion. Only poptGetNextOpt() can return this
error.

POPT_ERROR_BADQUOTE
A parsed string has a quotation mismatch (such as a single
quotation mark). poptParseArgvString(), poptReadConfigFile(),
or poptReadDefaultConfig() can return this error.

POPT_ERROR_ERRNO
A system call returned with an error, and errno still contains
the error from the system call. Both poptReadConfigFile() and
poptReadDefaultConfig() can return this error.

POPT_ERROR_BADNUMBER
A conversion from a string to a number (int or long) failed
due to the string containing non-numeric characters. This
occurs when poptGetNextOpt() is processing an argument of type
POPT_ARG_INT, POPT_ARG_SHORT, POPT_ARG_LONG,
POPT_ARG_LONGLONG, POPT_ARG_FLOAT, or POPT_ARG_DOUBLE.

POPT_ERROR_OVERFLOW
A string-to-number conversion failed because the number was
too large or too small. Like POPT_ERROR_BADNUMBER, this error
can occur only when poptGetNextOpt() is processing an
argument of type POPT_ARG_INT, POPT_ARG_SHORT, POPT_ARG_LONG,
POPT_ARG_LONGLONG, POPT_ARG_FLOAT, or POPT_ARG_DOUBLE.

POPT_ERROR_BADOPERATION
More than one logical operation (AND, OR, XOR) was specified
for an option, or POPT_ARGFLAG_RANDOM was specified but the
platform does not support the random() function. This can be
returned only by poptSaveLongLong(), poptSaveLong(),
poptSaveInt(), poptSaveShort() and poptGetNextOpt().

POPT_ERROR_NULLARG
An operation was invoked on a null target arg (including zero-
length string arguments). In the poptBitsArgs() case, this
includes an empty leftover argv array. This can only be
returned by the poptBits*() and poptSave*() functions,
poptConfigFileToString() and poptGetNextOpt().

POPT_ERROR_MALLOC
Memory allocation failed. This can only be returned by
poptReadFile(), poptDupArgv(), poptParseArgvString(),
poptConfigFileToString() and poptGetNextOpt().

POPT_ERROR_BADCONFIG
The popt configuration files are corrupted. This can only be
returned by poptReadConfigFile() and poptReadConfigFiles().

Two functions are available to make it easy for applications to
provide good error messages.

const char *const poptStrerror(const int error);
This function takes a popt error code and returns a string
describing the error, just as with the standard strerror()
function.

const char * poptBadOption(poptContext con, int flags);
If an error occurred during poptGetNextOpt(), this function
returns the option that caused the error. If the flags
argument is set to POPT_BADOPTION_NOALIAS, the outermost
option is returned. Otherwise, flags should be 0, and the
option that is returned may have been specified through an
alias.

These two functions make popt error handling trivial for most
applications. When an error is detected from most of the functions,
an error message is printed along with the error string from
poptStrerror(). When an error occurs during argument parsing, code
similar to the following displays a useful error message:

fprintf(stderr, "%s: %s\n",
poptBadOption(optCon, POPT_BADOPTION_NOALIAS),
poptStrerror(rc));

OPTION ALIASING

One of the primary benefits of using popt over getopt() is the
ability to use option aliasing. This lets the user specify options
that popt expands into other options when they are specified. If the
standard grep program made use of popt, users could add a --text
option that expanded to -i -n -E -2 to let them more easily find
information in text files.

1. SPECIFYING ALIASES
Aliases are normally specified in two places: /etc/popt and the .popt
file in the user's home directory (found through the HOME
environment variable). Both files have the same format, an arbitrary
number of lines formatted like this:

appname alias newoption expansion

The appname is the name of the application, which must be the same
as the name parameter passed to poptGetContext(). This allows each
file to specify aliases for multiple programs. The alias keyword
specifies that an alias is being defined; currently popt
configuration files support only aliases, but other abilities may be
added in the future. The next option is the option that should be
aliased, and it may be either a short or a long option. The rest of
the line specifies the expansion for the alias. It is parsed
similarly to a shell command, which allows \, ", and ' to be used for
quoting. If a backslash is the final character on a line, the next
line in the file is assumed to be a logical continuation of the line
containing the backslash, just as in shell.

The following entry would add a --text option to the grep command,
as suggested at the beginning of this section.

grep alias --text -i -n -E -2

2. ENABLING ALIASES
An application must enable alias expansion for a poptContext before
calling poptGetNextArg() for the first time. There are three
functions that define aliases for a context:

int poptReadDefaultConfig(poptContext con, int flags);
This function reads aliases from /etc/popt and the .popt file
in the user's home directory. Currently, flags should be
NULL, as it is provided only for future expansion.

int poptReadConfigFile(poptContext con, char * fn);
The file specified by fn is opened and parsed as a popt
configuration file. This allows programs to use program-
specific configuration files.

int poptAddAlias(poptContext con, struct poptAlias alias,
int flags);
Occasionally, processes want to specify aliases without having
to read them from a configuration file. This function adds a
new alias to a context. The flags argument should be 0, as it
is currently reserved for future expansion. The new alias is
specified as a struct poptAlias, which is defined as:

struct poptAlias {
const char * longName; /* may be NULL */
char shortName; /* may be '\0' */
int argc;
const char ** argv; /* must be free()able */
};

The first two elements, longName and shortName, specify the
option that is aliased. The final two, argc and argv, define
the expansion to use when the aliases option is encountered.

PARSING ARGUMENT STRINGS

Although popt is usually used for parsing arguments already divided
into an argv-style array, some programs need to parse strings that
are formatted identically to command lines. To facilitate this, popt
provides a function that parses a string into an array of strings,
using rules similar to normal shell parsing.

#include <popt.h>
int poptParseArgvString(char * s, int * argcPtr,
char *** argvPtr);
int poptDupArgv(int argc, const char ** argv, int * argcPtr,
const char *** argvPtr);

The string s is parsed into an argv-style array. The integer pointed
to by the argcPtr parameter contains the number of elements parsed,
and the final argvPtr parameter contains the address of the newly
created array. The routine poptDupArgv() can be used to make a copy
of an existing argument array.

The argvPtr created by poptParseArgvString() or poptDupArgv() is
suitable to pass directly to poptGetContext(). Both routines return
a single dynamically allocated contiguous block of storage and should
be free()ed when the application is finished with the storage.

HANDLING EXTRA ARGUMENTS

Some applications implement the equivalent of option aliasing but
need to do so through special logic. The poptStuffArgs() function
allows an application to insert new arguments into the current
poptContext.

#include <popt.h>
int poptStuffArgs(poptContext con, const char ** argv);

The passed argv must have a NULL pointer as its final element. When
poptGetNextOpt() is next called, the "stuffed" arguments are the
first to be parsed. popt returns to the normal arguments once all the
stuffed arguments have been exhausted.

EXAMPLE

The following example is a simplified version of the program "robin"
which appears in Chapter 15 of the text cited below. Robin has been
stripped of everything but its argument-parsing logic, slightly
reworked, and renamed "parse." It may prove useful in illustrating at
least some of the features of the extremely rich popt library.

#include <popt.h>
#include <stdio.h>
#include <stdlib.h>

void usage(poptContext optCon, int exitcode, char *error, char *addl) {
poptPrintUsage(optCon, stderr, 0);
if (error) fprintf(stderr, "%s: %s\n", error, addl);
exit(exitcode);
}

int main(int argc, char *argv[]) {
int c; /* used for argument parsing */
int i = 0; /* used for tracking options */
int speed = 0; /* used in argument parsing to set speed */
int raw = 0; /* raw mode? */
int j;
char buf[BUFSIZ+1];
const char *portname;
poptContext optCon; /* context for parsing command-line options */

struct poptOption optionsTable[] = {
{ "bps", 'b', POPT_ARG_INT, &speed, 0,
"signaling rate in bits-per-second", "BPS" },
{ "crnl", 'c', 0, 0, 'c',
"expand cr characters to cr/lf sequences", NULL },
{ "hwflow", 'h', 0, 0, 'h',
"use hardware (RTS/CTS) flow control", NULL },
{ "noflow", 'n', 0, 0, 'n',
"use no flow control", NULL },
{ "raw", 'r', 0, &raw, 0,
"don't perform any character conversions", NULL },
{ "swflow", 's', 0, 0, 's',
"use software (XON/XOF) flow control", NULL } ,
POPT_AUTOHELP
{ NULL, 0, 0, NULL, 0 }
};

optCon = poptGetContext(NULL, argc, argv, optionsTable, 0);
poptSetOtherOptionHelp(optCon, "[OPTIONS]* <port>");

if (argc < 2) {
poptPrintUsage(optCon, stderr, 0);
exit(1);
}

/* Now do options processing, get portname */
while ((c = poptGetNextOpt(optCon)) >= 0) {
switch (c) {
case 'c':
buf[i++] = 'c';
break;
case 'h':
buf[i++] = 'h';
break;
case 's':
buf[i++] = 's';
break;
case 'n':
buf[i++] = 'n';
break;
}
}
portname = poptGetArg(optCon);
if((portname == NULL) || !(poptPeekArg(optCon) == NULL))
usage(optCon, 1, "Specify a single port", ".e.g., /dev/cua0");

if (c < -1) {
/* an error occurred during option processing */
fprintf(stderr, "%s: %s\n",
poptBadOption(optCon, POPT_BADOPTION_NOALIAS),
poptStrerror(c));
return 1;
}

/* Print out options, portname chosen */
printf("Options chosen: ");
for(j = 0; j < i ; j++)
printf("-%c ", buf[j]);
if(raw) printf("-r ");
if(speed) printf("-b %d ", speed);
printf("\nPortname chosen: %s\n", portname);

poptFreeContext(optCon);
exit(0);
}

RPM, a popular Linux package management program, makes heavy use of
popt's features. Many of its command-line arguments are implemented
through popt aliases, which makes RPM an excellent example of how to
take advantage of the popt library. For more information on RPM, see
http://www.rpm.org. The popt source code distribution includes test
program(s) which use all of the features of the popt libraries in
various ways. If a feature isn't working for you, the popt test code
is the first place to look.

BUGS

None presently known.

AUTHOR

Erik W. Troan <ewt@redhat.com>

This man page is derived in part from Linux Application Development
by Michael K. Johnson and Erik W. Troan, Copyright (c) 1998 by
Addison Wesley Longman, Inc., and included in the popt documentation
with the permission of the Publisher and the appreciation of the
Authors.

Thanks to Robert Lynch for his extensive work on this man page.