---
name: sysopen
status: documented
runtime: pp
source: src/runtime/pp/fileio.rs
---
```{index} single: sysopen; Perl built-in (pp runtime)
```

# sysopen

## Synopsis

```perl
use Fcntl;
sysopen(my $fh, $filename, O_RDWR | O_CREAT, 0644);
sysopen(FH, $path, O_WRONLY | O_TRUNC);
```

## Description

Opens a file using POSIX open(2) flags for precise mode control.

Unlike the high-level `open`, `sysopen` takes explicit POSIX mode
flags (from `Fcntl`) and an optional permissions mask.  The flags
are passed directly to the underlying `open(2)` system call.

Arguments on the stack (via mark): filehandle target, filename,
mode flags, and optional permissions (defaults to 0666, modified
by umask).

Returns 1 on success (the filehandle is stored in the first
argument) or undef on failure.

## See also

open, close, Fcntl