FileCache

Section: Perl Programmers Reference Guide (3pm)
Updated: 2021-03-31
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NAME

FileCache - keep more files open than the system permits

SYNOPSIS

    no strict 'refs';

    use FileCache;
    # or
    use FileCache maxopen => 16;

    cacheout $mode, $path;
    # or
    cacheout $path;
    print $path @data;

    $fh = cacheout $mode, $path;
    # or
    $fh = cacheout $path;
    print $fh @data;

DESCRIPTION

The "cacheout" function will make sure that there's a filehandle open for reading or writing available as the pathname you give it. It automatically closes and re-opens files if you exceed your system's maximum number of file descriptors, or the suggested maximum maxopen.

cacheout EXPR

The 1-argument form of cacheout will open a file for writing ('>') on it's first use, and appending ('>>') thereafter.

Returns EXPR on success for convenience. You may neglect the return value and manipulate EXPR as the filehandle directly if you prefer.

cacheout MODE, EXPR

The 2-argument form of cacheout will use the supplied mode for the initial and subsequent openings. Most valid modes for 3-argument "open" are supported namely; '>', '+>', '<', '<+', '>>', '|-' and '-|'

To pass supplemental arguments to a program opened with '|-' or '-|' append them to the command string as you would system EXPR.

Returns EXPR on success for convenience. You may neglect the return value and manipulate EXPR as the filehandle directly if you prefer.

CAVEATS

While it is permissible to "close" a FileCache managed file, do not do so if you are calling "FileCache::cacheout" from a package other than which it was imported, or with another module which overrides "close". If you must, use "FileCache::cacheout_close".

Although FileCache can be used with piped opens ('-|' or '|-') doing so is strongly discouraged. If FileCache finds it necessary to close and then reopen a pipe, the command at the far end of the pipe will be reexecuted - the results of performing IO on FileCache'd pipes is unlikely to be what you expect. The ability to use FileCache on pipes may be removed in a future release.

FileCache does not store the current file offset if it finds it necessary to close a file. When the file is reopened, the offset will be as specified by the original "open" file mode. This could be construed to be a bug.

The module functionality relies on symbolic references, so things will break under 'use strict' unless 'no strict ``refs''' is also specified.

BUGS

sys/param.h lies with its "NOFILE" define on some systems, so you may have to set maxopen yourself.