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CORE(5)                  DragonFly File Formats Manual                 CORE(5)


NAME

     core -- memory image file format


SYNOPSIS

     #include <sys/param.h>


DESCRIPTION

     A small number of signals which cause abnormal termination of a process
     also cause a record of the process's in-core state to be written to disk
     for later examination by one of the available debuggers.  (See
     sigaction(2).)  This memory image is written to a file named by default
     programname.core in the working directory; provided the terminated
     process had write permission in the directory, and provided the abnormal-
     ity did not cause a system crash.  (In this event, the decision to save
     the core file is arbitrary, see savecore(8).)

     The maximum size of a core file is limited by setrlimit(2).  Files which
     would be larger than the limit are not created.

     The name of the file is controlled via the sysctl(8) variable
     kern.corefile.  The contents of this variable describes a filename to
     store the core image to.  This filename can be absolute, or relative
     (which will resolve to the current working directory of the program gen-
     erating it).  Any sequence of %N in this filename template will be
     replaced by the process name, %P by the processes PID, and %U by the UID.
     The name defaults to %N.core, yielding the traditional DragonFly behav-
     iour.

     By default, a process that changes user or group credentials whether real
     or effective will not create a corefile.  This behaviour can be changed
     to generate a core dump by setting the sysctl(8) variable
     kern.sugid_coredump to 1.

     The core file consists of the u. area, whose size (in pages) is defined
     by the UPAGES manifest in the <sys/param.h> file.  The u. area starts
     with a user structure as given in <sys/user.h>.  The remainder of the
     core file consists of the data pages followed by the stack pages of the
     process image.  The amount of data space image in the core file is given
     (in pages) by the variable u_dsize in the u. area.  The amount of stack
     image in the core file is given (in pages) by the variable u_ssize in the
     u. area.  The size of a ``page'' is given by the constant PAGE_SIZE (also
     from <sys/param.h>).


EXAMPLES

     In order to store all core images in per-user private areas under
     /var/coredumps, the following sysctl(8) command can be used:

           sysctl kern.corefile="/var/coredumps/%U/%N.core"


SEE ALSO

     gdb(1), kgdb(1), setrlimit(2), sigaction(2), sysctl(8)


HISTORY

     A core file format appeared in Version 6 AT&T UNIX.

DragonFly 3.5                   January 9, 2002                  DragonFly 3.5

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