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.\" Copyright (c) 1983, 1990, 1992, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"
.\"	@(#)gcore.1	8.2 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd April 24, 2021
.Dt GCORE 1
.Os
.Sh NAME
.Nm gcore
.Nd get core images of running process
.Sh SYNOPSIS
.Nm
.Op Fl f
.Op Fl k
.Op Fl c Ar core
.Op Ar executable
.Ar pid
.Sh DESCRIPTION
The
.Nm
utility creates a core image of the specified process,
suitable for use with
.Xr gdb 1 .
By default, the core is written to the file
.Dq Pa core.<pid> .
The process identifier,
.Ar pid ,
must be given on the command line.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl c
Write the core file to the specified file instead of
.Dq Pa core.<pid> .
.It Fl f
Dumps all available segments, excluding only malformed and undumpable
segments.
Unlike the default invocation, this flag dumps mappings of devices which
may invalidate the state of device transactions or trigger other unexpected
behavior.
As a result, this flag should only be used when the behavior of the
application and any devices it has mapped is fully understood and any side
effects can be controlled or tolerated.
.It Fl k
Use the
.Xr ptrace 2
.Dv PT_COREDUMP
kernel facility to write the core dump, instead of reading the process'
memory and constructing the dump file in
.Nm
itself.
This is faster, and the dump is written by the
same kernel code that writes core dumps upon fatal signals.
.El
.Sh FILES
.Bl -tag -width /var/log/messages -compact
.It Pa core.<pid>
the core image
.El
.Sh HISTORY
A
.Nm
utility appeared in
.Bx 4.2 .
.Sh BUGS
Because of the
.Xr ptrace 2
usage
.Nm
may not work with processes which are actively being investigated with
.Xr truss 1
or
.Xr gdb 1 .
Additionally, interruptable sleeps may exit with EINTR.
.Pp
The
.Nm
utility is not compatible with the original
.Bx 4.2
version.