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.IX Title "nbdkit_timestamp 3"
.TH nbdkit_timestamp 3 2026-07-28 nbdkit-1.48.0 NBDKIT
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.SH NAME
nbdkit_timestamp \- generate a timestamp for log messages
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <nbdkit\-plugin.h>
\&
\& const char *nbdkit_timestamp (void);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\f(CW\*(C`nbdkit_timestamp\*(C'\fR generates a timestamp as a printable string which
may be added to debug or error messages (see \fBnbdkit_debug\fR\|(3),
\&\fBnbdkit_error\fR\|(3)).
.PP
It can be used like this:
.PP
.Vb 1
\& nbdkit_debug ("%s: this is a debug message", nbdkit_timestamp ());
.Ve
.PP
which would produce a debug message like this:
.PP
.Vb 1
\& debug: 2026\-01\-01 12:00:00.000333: this is a debug message
.Ve
.PP
The timestamps show the wallclock time in approximately ISO 8601
format, but less ugly.  They are always shown in UTC, in 24 hour
notation, to the nearest microsecond.  (On Windows, timestamps use the
same format but are rounded to the nearest millisecond.)
.PP
You can also separate the \fBnbdkit_timestamp()\fR call from the place where
it is used, allowing you to accurately timestamp, for example, the
point when a system call was invoked:
.PP
.Vb 7
\& const char *ts = nbdkit_timestamp ();
\& int r = pwrite (fd, ...);
\& if (r == \-1) {
\&   /* The error message shows the time that pwrite started. */
\&   nbdkit_error ("%s: pwrite: %m", ts);
\&   return \-1;
\& }
.Ve
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
The function returns a constant string allocated in thread\-local
storage.  The string is valid until the next call to
\&\f(CW\*(C`nbdkit_timestamp\*(C'\fR in the same thread.
.PP
It never returns \f(CW\*(C`NULL\*(C'\fR.  In the (very unlikely) case that there was
an error generating the timestamp, the string \f(CW"!"\fR is returned.
.SH "LANGUAGE BINDINGS"
.IX Header "LANGUAGE BINDINGS"
In \fBnbdkit\-ocaml\-plugin\fR\|(3):
.PP
.Vb 1
\& NBDKit.timestamp : unit \-> string
.Ve
.PP
In \fBnbdkit\-python\-plugin\fR\|(3):
.PP
.Vb 2
\& import nbdkit
\& ts = nbdkit.timestamp()
.Ve
.PP
In \fBnbdkit\-rust\-plugin\fR\|(3):
.PP
.Vb 2
\& use nbdkit::*;
\& pub fn timestamp() \-> String
.Ve
.SH HISTORY
.IX Header "HISTORY"
\&\f(CW\*(C`nbdkit_timestamp\*(C'\fR was added in nbdkit 1.48.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit_debug\fR\|(3),
\&\fBnbdkit_error\fR\|(3),
\&\fBnbdkit\-plugin\fR\|(3),
\&\fBnbdkit\-filter\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP \(bu 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS \*(Aq\*(AqAS IS\*(Aq\*(Aq AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.