optstr_get —
Options string management
#include <sys/optstr.h>
bool
  
  optstr_get(const
    char *optstr, const char
    *key, char *buf,
    size_t bufsize);
An options string is a list of key/value pairs represented in textual form. Each
  pair is expressed as ‘'key=value'’ and is separated from other
  pairs by one or more spaces. For example:
key1=value1 key2=value2 key3=value3
 
Options strings are used to pass information between userland
    programs and the kernel in a binary-agnostic way. This makes them endianness
    and ABI independent.
The following functions are provided to manage options strings:
  - optstr_get(optstr,
    key, buf,
    bufsize)
- Scans the optstr options string looking for the key
      key and stores its value in the buffer pointed to by
      buf copying a maximum of
      bufsize bytes. Returns ‘true’ if the
      key was found or ‘false’ otherwise, in which case
      buf is left unmodified.
The options string management functions are implemented within the files
  sys/kern/subr_optstr.c and
  sys/sys/optstr.h.
Options strings appeared in NetBSD 4.0.