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 Opening the database.
 *********************
 
    Initialize `gdbm' system. If the file has a size of zero bytes, a
 file initialization procedure is performed, setting up the initial
 structure in the file.
 
    The procedure for opening a `gdbm' file is:
 
      GDBM_FILE dbf;
      
      dbf = gdbm_open(name, block_size, flags, mode, fatal_func);
 
    The parameters are:
 
 char *name
      The name of the file (the complete name, `gdbm' does not append any
      characters to this name).
 
 int block_size
      It is used during initialization to determine the size of various
      constructs. It is the size of a single transfer from disk to
      memory. This parameter is ignored if the file has been previously
      initialized. The minimum size is 512.  If the value is less than
      512, the file system blocksize is used, otherwise the value of
      `block_size' is used.
 
 int flags
      If `flags' is set to GDBM_READER, the user wants to just read the
      database and any call to `gdbm_store' or `gdbm_delete' will fail.
      Many readers can access the database at the same time. If `flags'
      is set to GDBM_WRITER, the user wants both read and write access
      to the database and requires exclusive access. If `flags' is set
      to GDBM_WRCREAT, the user wants both read and write access to the
      database and if the database does not exist, create a new one. If
      `flags' is set to GDBM_NEWDB, the user want a new database
      created, regardless of whether one existed, and wants read and
      write access to the new database.  The following may also be
      logically or'd into the database flags: GDBM_SYNC, which causes
      all database operations to be synchronized to the disk, and
      GDBM_NOLOCK, which prevents the library from performing any
      locking on the database file.  The option GDBM_FAST is now
      obsolete, since `gdbm' defaults to no-sync mode.  Any error
      detected will cause a return value of NULL and an appropriate
      value will be in `gdbm_errno' (see Variables). If no errors occur,
      a pointer to the `gdbm' file descriptor will be returned.
 
 int mode
      File mode (see chmod(2) and open(2) if the file is created).
 
 void (*fatal_func) ()
      A function for `gdbm' to call if it detects a fatal error. The only
      parameter of this function is a string. If the value of NULL is
      provided, `gdbm' will use a default function.
 
    The return value, `dbf', is the pointer needed by all other
 functions to access that `gdbm' file. If the return is the NULL pointer,
 `gdbm_open' was not successful. The errors can be found in `gdbm_errno'
 for `gdbm' errors and in `errno' for file system errors (for error
 codes, see `gdbm.h').
 
    In all of the following calls, the parameter `dbf' refers to the
 pointer returned from `gdbm_open'.
 
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