PerlIO::mmap(3pm) Perl Programmers Reference Guide PerlIO::mmap(3pm)

# [NAME](#NAME)

PerlIO::mmap - Memory mapped IO

# [SYNOPSIS](#SYNOPSIS)

```
 open my $fh, '<:mmap', $filename;
```

# [DESCRIPTION](#DESCRIPTION)

This layer does "read" and "write" operations by **mmap()**ing the file if possible, but falls back to the default behavior if not.

# [IMPLEMENTATION NOTE](#IMPLEMENTATION_NOTE)

"PerlIO::mmap" only exists to use XSLoader to load C code that provides support for using memory mapped IO. One does not need to explicitly "use PerlIO::mmap;".

2026-10-26 perl v5.44.0

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Document: PerlIO::mmap(3pm) from perl 5.44.0-r3 (Chainguard OS)
Source: https://github.com/Perl/perl5.git