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.\" ========================================================================
.\"
.IX Title "Fcntl 3perl"
.TH Fcntl 3perl "2018-11-29" "perl v5.24.1" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
Fcntl \- load the C Fcntl.h defines
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&    use Fcntl;
\&    use Fcntl qw(:DEFAULT :flock);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module is just a translation of the C \fIfcntl.h\fR file.
Unlike the old mechanism of requiring a translated \fIfcntl.ph\fR
file, this uses the \fBh2xs\fR program (see the Perl source distribution)
and your native C compiler.  This means that it has a 
far more likely chance of getting the numbers right.
.SH "NOTE"
.IX Header "NOTE"
Only \f(CW\*(C`#define\*(C'\fR symbols get translated; you must still correctly
pack up your own arguments to pass as args for locking functions, etc.
.SH "EXPORTED SYMBOLS"
.IX Header "EXPORTED SYMBOLS"
By default your system's F_* and O_* constants (eg, F_DUPFD and
O_CREAT) and the \s-1FD_CLOEXEC\s0 constant are exported into your namespace.
.PP
You can request that the \fIflock()\fR constants (\s-1LOCK_SH, LOCK_EX, LOCK_NB\s0
and \s-1LOCK_UN\s0) be provided by using the tag \f(CW\*(C`:flock\*(C'\fR.  See Exporter.
.PP
You can request that the old constants (\s-1FAPPEND, FASYNC, FCREAT,
FDEFER, FEXCL, FNDELAY, FNONBLOCK, FSYNC, FTRUNC\s0) be provided for
compatibility reasons by using the tag \f(CW\*(C`:Fcompat\*(C'\fR.  For new
applications the newer versions of these constants are suggested
(O_APPEND, O_ASYNC, O_CREAT, O_DEFER, O_EXCL, O_NDELAY, O_NONBLOCK,
O_SYNC, O_TRUNC).
.PP
For ease of use also the SEEK_* constants (for \fIseek()\fR and \fIsysseek()\fR,
e.g. \s-1SEEK_END\s0) and the S_I* constants (for \fIchmod()\fR and \fIstat()\fR) are
available for import.  They can be imported either separately or using
the tags \f(CW\*(C`:seek\*(C'\fR and \f(CW\*(C`:mode\*(C'\fR.
.PP
Please refer to your native \fIfcntl\fR\|(2), \fIopen\fR\|(2), \fIfseek\fR\|(3), \fIlseek\fR\|(2)
(equal to Perl's \fIseek()\fR and \fIsysseek()\fR, respectively), and \fIchmod\fR\|(2)
documentation to see what constants are implemented in your system.
.PP
See perlopentut to learn about the uses of the O_* constants
with \fIsysopen()\fR.
.PP
See \*(L"seek\*(R" in perlfunc and \*(L"sysseek\*(R" in perlfunc about the SEEK_* constants.
.PP
See \*(L"stat\*(R" in perlfunc about the S_I* constants.