312 lines
8.1 KiB
Groff
312 lines
8.1 KiB
Groff
.\" Copyright (c) 1999 Kungliga Tekniska Högskolan
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.\" $Id: getarg.3,v 1.3 2001/01/11 16:16:30 assar Exp $
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.Dd September 24, 1999
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.Dt GETARG 3
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.Os ROKEN
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.Sh NAME
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.Nm getarg ,
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.Nm arg_printusage
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.Nd collect command line options
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.Sh SYNOPSIS
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.Fd #include <getarg.h>
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.Ft int
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.Fn getarg "struct getargs *args" "size_t num_args" "int argc" "char **argv" "int *optind"
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.Ft void
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.Fn arg_printusage "struct getargs *args" "size_t num_args" "const char *progname" "const char *extra_string"
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.Sh DESCRIPTION
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.Fn getarg
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collects any command line options given to a program in an easily used way.
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.Fn arg_printusage
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pretty-prints the available options, with a short help text.
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.Pp
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.Fa args
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is the option specification to use, and it's an array of
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.Fa struct getargs
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elements.
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.Fa num_args
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is the size of
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.Fa args
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(in elements).
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.Fa argc
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and
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.Fa argv
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are the argument count and argument vector to extract option from.
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.Fa optind
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is a pointer to an integer where the index to the last processed
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argument is stored, it must be initialised to the first index (minus
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one) to process (normally 0) before the first call.
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.Pp
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.Fa arg_printusage
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take the same
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.Fa args
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and
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.Fa num_args
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as getarg;
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.Fa progname
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is the name of the program (to be used in the help text), and
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.Fa extra_string
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is a string to print after the actual options to indicate more
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arguments. The usefulness of this function is realised only be people
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who has used programs that has help strings that doesn't match what
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the code does.
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.Pp
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The
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.Fa getargs
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struct has the following elements.
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.Bd -literal
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struct getargs{
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const char *long_name;
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char short_name;
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enum { arg_integer,
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arg_string,
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arg_flag,
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arg_negative_flag,
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arg_strings,
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arg_double,
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arg_collect
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} type;
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void *value;
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const char *help;
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const char *arg_help;
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};
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.Ed
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.Pp
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.Fa long_name
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is the long name of the option, it can be
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.Dv NULL ,
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if you don't want a long name.
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.Fa short_name
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is the characted to use as short option, it can be zero. If the option
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has a value the
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.Fa value
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field gets filled in with that value interpreted as specified by the
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.Fa type
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field.
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.Fa help
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is a longer help string for the option as a whole, if it's
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.Dv NULL
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the help text for the option is omitted (but it's still displayed in
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the synopsis).
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.Fa arg_help
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is a description of the argument, if
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.Dv NULL
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a default value will be used, depending on the type of the option:
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.Pp
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.Bl -hang -width arg_negative_flag
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.It arg_integer
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the argument is a signed integer, and
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.Fa value
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should point to an
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.Fa int .
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.It Fa arg_string
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the argument is a string, and
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.Fa value
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should point to a
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.Fa char* .
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.It Fa arg_flag
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the argument is a flag, and
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.Fa value
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should point to a
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.Fa int .
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It gets filled in with either zero or one, depending on how the option
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is given, the normal case beeing one. Note that if the option isn't
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given, the value isn't altered, so it should be initialised to some
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useful default.
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.It Fa arg_negative_flag
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this is the same as
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.Fa arg_flag
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but it reverses the meaning of the flag (a given short option clears
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the flag), and the synopsis of a long option is negated.
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.It Fa arg_strings
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the argument can be given multiple times, and the values are collected
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in an array;
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.Fa value
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should be a pointer to a
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.Fa struct getarg_strings
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structure, which holds a length and a string pointer.
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.It Fa arg_double
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argument is a double precision floating point value, and
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.Fa value
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should point to a
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.Fa double .
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.It Fa arg_collect
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allows more fine-grained control of the option parsing process.
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.Fa value
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should be a pointer to a
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.Fa getarg_collect_info
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structure:
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.Bd -literal
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typedef int (*getarg_collect_func)(int short_opt,
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int argc,
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char **argv,
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int *optind,
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int *optarg,
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void *data);
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typedef struct getarg_collect_info {
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getarg_collect_func func;
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void *data;
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} getarg_collect_info;
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.Ed
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.Pp
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With the
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.Fa func
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member set to a function to call, and
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.Fa data
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to some application specific data. The parameters to the collect function are:
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.Bl -inset
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.It Fa short_flag
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non-zero if this call is via a short option flag, zero otherwise
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.It Fa argc , argv
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the whole argument list
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.It Fa optind
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pointer to the index in argv where the flag is
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.It Fa optarg
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pointer to the index in argv[*optind] where the flag name starts
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.It Fa data
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application specific data
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.El
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.Pp
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You can modify
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.Fa *optind ,
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and
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.Fa *optarg ,
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but to do this correct you (more or less) have to know about the inner
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workings of getarg.
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.Pp
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You can skip parts of arguments by increasing
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.Fa *optarg
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(you could
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implement the
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.Fl z Ns Ar 3
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set of flags from
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.Nm gzip
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with this), or whole argument strings by increasing
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.Fa *optind
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(let's say you want a flag
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.Fl c Ar x y z
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to specify a coordinate); if you also have to set
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.Fa *optarg
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to a sane value.
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.Pp
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The collect function should return one of
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.Dv ARG_ERR_NO_MATCH , ARG_ERR_BAD_ARG , ARG_ERR_NO_ARG
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on error, zero otherwise.
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.Pp
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For your convenience there is a function,
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.Fn getarg_optarg ,
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that returns the traditional argument string, and you pass it all
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arguments, sans data, that where given to the collection function.
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.Pp
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Don't use this more this unless you absolutely have to.
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.El
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.Pp
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Option parsing is similar to what
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.Xr getopt
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uses. Short options without arguments can be compressed
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.Pf ( Fl xyz
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is the same as
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.Fl x y z ) ,
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and short
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options with arguments take these as either the rest of the
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argv-string or as the next option
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.Pf ( Fl o Ns Ar foo ,
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or
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.Fl o Ar foo ) .
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.Pp
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Long option names are prefixed with -- (double dash), and the value
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with a = (equal),
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.Fl -foo= Ns Ar bar .
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Long option flags can either be specified as they are
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.Pf ( Fl -help ) ,
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or with an (boolean parsable) option
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.Pf ( Fl -help= Ns Ar yes ,
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.Fl -help= Ns Ar true ,
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or similar), or they can also be negated
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.Pf ( Fl -no-help
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is the same as
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.Fl -help= Ns no ) ,
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and if you're really confused you can do it multiple times
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.Pf ( Fl -no-no-help= Ns Ar false ,
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or even
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.Fl -no-no-help= Ns Ar maybe ) .
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.Sh EXAMPLE
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.Bd -literal
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#include <stdio.h>
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#include <string.h>
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#include <getarg.h>
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char *source = "Ouagadougou";
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char *destination;
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int weight;
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int include_catalog = 1;
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int help_flag;
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struct getargs args[] = {
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{ "source", 's', arg_string, &source,
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"source of shippment", "city" },
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{ "destination", 'd', arg_string, &destination,
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"destination of shippment", "city" },
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{ "weight", 'w', arg_integer, &weight,
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"weight of shippment", "tons" },
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{ "catalog", 'c', arg_negative_flag, &include_catalog,
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"include product catalog" },
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{ "help", 'h', arg_flag, &help_flag }
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};
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int num_args = sizeof(args) / sizeof(args[0]); /* number of elements in args */
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const char *progname = "ship++";
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int
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main(int argc, char **argv)
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{
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int optind = 0;
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if (getarg(args, num_args, argc, argv, &optind)) {
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arg_printusage(args, num_args, progname, "stuff...");
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exit (1);
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}
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if (help_flag) {
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arg_printusage(args, num_args, progname, "stuff...");
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exit (0);
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}
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if (destination == NULL) {
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fprintf(stderr, "%s: must specify destination\en", progname);
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exit(1);
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}
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if (strcmp(source, destination) == 0) {
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fprintf(stderr, "%s: destination must be different from source\en");
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exit(1);
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}
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/* include more stuff here ... */
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exit(2);
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}
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.Ed
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.Pp
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The output help output from this program looks like this:
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.Bd -literal
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$ ship++ --help
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Usage: ship++ [--source=city] [-s city] [--destination=city] [-d city]
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[--weight=tons] [-w tons] [--no-catalog] [-c] [--help] [-h] stuff...
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-s city, --source=city source of shippment
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-d city, --destination=city destination of shippment
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-w tons, --weight=tons weight of shippment
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-c, --no-catalog include product catalog
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.Ed
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.Sh BUGS
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It should be more flexible, so it would be possible to use other more
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complicated option syntaxes, such as what
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.Xr ps 1 ,
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and
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.Xr tar 1 ,
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uses, or the AFS model where you can skip the flag names as long as
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the options come in the correct order.
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.Pp
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Options with multiple arguments should be handled better.
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.Pp
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Should be integreated with SL.
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.Pp
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It's very confusing that the struct you pass in is called getargS.
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.Sh SEE ALSO
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.Xr getopt 3
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