---
name: "wnargp"
section: "3"
platform: "linux"
package: "libwn-dev"
version: "6.0-17"
release: "Debian 4.0 (Etch)"
platforms: ["linux"]
url: "https://new.carta.tech/wnargp"
---

# wnargp(3)

parse UNIX-style arguments

## NAME

wn\_parse\_args, wn\_push\_parse\_args\_error\_print, wn\_pop\_parse\_args\_error\_print - parse UNIX-style arguments

## SYNOPSIS

```
#include <wn/wnargp.h>

wn_parse_args(argc,argv,arg_format_array)
int argc;
char *argv[];
wn_arg_format arg_format_array[];

wn_push_parse_args_error_print(ppassed_print_error)
void (*ppassed_print_error)(/* string */);

wn_pop_parse_args_error_print()

```

## DESCRIPTION

This package allows one to easily parse *argc*-*argv* arguments in the standard UNIX way.

**wn\_parse\_args** parses *argv* according to the format specified in *arg\_format\_array*.  *argv* has *argc* arguments.  The following types of arguments are recognized:

1\)  Keyword boolean.  The presence or absence of a flag controls a boolean variable in your C program.  A \<flag\> is any string immediately preceded by a '-' character.  Specify a keyword boolean  by placing a **WN\_KEY\_BOOL** call in your format array. Position in the argument list is ignored.

2\)  Keyword string.  A keyword string is a flag followed by a string argument.  If this argument is present, a variable in your program is set to the value of the string argument. Position in the argument list is ignored.  Specify a keyword string by placing a **WN\_KEY\_STRING** call in your format array.

3\)  Positional string.  A positional string is a string argment with no associated flag.  Its meaning depends on its position relative to other positional strings.  If this argument is present, a variable in your program is set to the value of the string argument.  Specify a keyword boolean flag by placing  a **WN\_POS\_STRING** call in your format array.  The order in which **WN\_POS\_STRING** calls appear in the format array determine the order the positional string arguments are expected in the argument list.

Key strings or positional strings may be optional or required. Not including a required argument is an argument syntax error.

All argument syntax errors (that is, the user types in the wrong arguments to a command) cause a standard UNIX command usage  message to be printed.  By default, the message goes to  standard error and the program exits.  This may be changed  by pushing a different print routine using  **wn\_push\_parse\_args\_error\_print** and **wn\_pop\_parse\_args\_error\_print**.

## EXAMPLES

Consider the code fragment below.

```
#include <wn/wnargp.h>
bool recover;
char *control_filename,*error_filename,*in_filename,*out_filename;
main(argc,argv)
int argc;
char *argv[];
{
static wn_arg_format arg_format_array[] =
{
WN_KEY_BOOL(&recover,>r"),
WN_KEY_STRING(&control_filename,>g","control_file",WN_REQUIRED),
WN_KEY_STRING(&error_filename,>log","error_file",WN_OPTIONAL),
WN_POS_STRING(&in_filename,>in_file",WN_REQUIRED),
WN_POS_STRING(&out_filename,>out_file",WN_OPTIONAL),
WN_ARG_TERMINATE
};
error_filename = <dastoinf.log>;  /* defaults */
inf_filename = <net.inf>;
wn_parse_args(argc,argv,arg_format_array);
}
```

Typing bad arguments produces the message:

usage: command \[-r\] -g control\_file \[-log error\_file\] in\_file \[out\_file\]

## SEE ALSO

wnargv

## AUTHOR

Will Naylor