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NDBM_File (3)
  • NDBM_File (3) ( Solaris man: Библиотечные вызовы )
  • >> NDBM_File (3) ( Разные man: Библиотечные вызовы )
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    NAME

    NDBM_File - Tied access to ndbm files
     
    

    SYNOPSIS

      use Fcntl;   # For O_RDWR, O_CREAT, etc.
      use NDBM_File;
    
    

      tie(%h, 'NDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
        or die "Couldn't tie NDBM file 'filename': $!; aborting";
    
    

      # Now read and change the hash
      $h{newkey} = newvalue;
      print $h{oldkey};
      ...
    
    

      untie %h;
    
    
     

    DESCRIPTION

    "NDBM_File" establishes a connection between a Perl hash variable and a file in NDBM_File format;. You can manipulate the data in the file just as if it were in a Perl hash, but when your program exits, the data will remain in the file, to be used the next time your program runs.

    Use "NDBM_File" with the Perl built-in "tie" function to establish the connection between the variable and the file. The arguments to "tie" should be:

    1.
    The hash variable you want to tie.
    2.
    The string "NDBM_File". (Ths tells Perl to use the "NDBM_File" package to perform the functions of the hash.)
    3.
    The name of the file you want to tie to the hash.
    4.
    Flags. Use one of:
    O_RDONLY
    Read-only access to the data in the file.
    O_WRONLY
    Write-only access to the data in the file.
    O_RDWR
    Both read and write access.

    If you want to create the file if it does not exist, add "O_CREAT" to any of these, as in the example. If you omit "O_CREAT" and the file does not already exist, the "tie" call will fail.

    5.
    The default permissions to use if a new file is created. The actual permissions will be modified by the user's umask, so you should probably use 0666 here. (See ``umask'' in perlfunc.)
     

    DIAGNOSTICS

    On failure, the "tie" call returns an undefined value and probably sets $! to contain the reason the file could not be tied.  

    ndbm store returned -1, errno 22, key ... at ...

    This warning is emitted when you try to store a key or a value that is too long. It means that the change was not recorded in the database. See BUGS AND WARNINGS below.  

    BUGS AND WARNINGS

    There are a number of limits on the size of the data that you can store in the NDBM file. The most important is that the length of a key, plus the length of its associated value, may not exceed 1008 bytes.

    See ``tie'' in perlfunc, perldbmfilter, Fcntl


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    DIAGNOSTICS
    ndbm store returned -1, errno 22, key ... at ...
    BUGS AND WARNINGS


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