core(4)                          UNIX System V                          core(4)


NAME
      core - core image file

DESCRIPTION
      The UNIX system writes out a core image of a process when it is
      terminated due to the receipt of some signals.  The core image is called
      core and is written in the process's working directory (provided it can
      be; normal access controls apply).  A process with an effective user ID
      different from the real user ID will not produce a core image.

      The core file contains all the process information pertinent to
      debugging: contents of hardware registers, process status and process
      data.  The format of a core file is object file specific.

      For ELF executable programs [see a.out(4)], the core file generated is
      also an ELF file, containing ELF program and file headers.  The etype
      field in the file header has type ETCORE.  The program header contains
      an entry for every loadable and writable segment that was part of the
      process address space, including shared library segments.  The contents
      of the segments themselves are also part of the core image.

      The program header of an ELF core file also contains a NOTE segment.
      This segment may contain the following entries.  Each has entry name
      "CORE" and presents the contents of a system structure:

      prstatust
            The entry containing this structure has a NOTE type of 1.  This
            structure contains things of interest to a debugger from the
            operating system's u-area, such as the general registers, signal
            dispositions, state, reason for stopping, process ID and so forth.
            The structure is defined in sys/procfs.h.

      fpregsett
            This entry is present only if the process used the floating-point
            hardware.  It has a NOTE type of 2 and contains the floating-point
            registers.  The fpregsett structure is defined in sys/regset.h.

      prpsinfot
            The entry containing this structure has a NOTE type of 3.  It
            contains information of interest to the ps(1) command, such as
            process status, cpu usage, "nice" value, controlling terminal, user
            ID, process ID, the name of the executable and so forth.  The
            structure is defined in sys/procfs.h.

      COFF executable programs produce core files consisting of two parts: the
      first section is a copy of the system's per-user data for the process,
      including the general registers.  The format of this section is defined
      in the header files sys/user.h and sys/reg.h.  The remainder of a COFF
      core image represents the actual contents of the process data space.





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core(4)                          UNIX System V                          core(4)


      The size of the core file created by a process may be controlled by the
      user [see getrlimit(2)].

SEE ALSO
      sdb(1), getrlimit(2), setuid(2), elf(3E), a.out(4), signal(5)
      crash(1M) in the System Administrator's Reference Manual
      The ``Object Files'' chapter in the Programmer's Guide: ANSI C and
      Programming Support Tools














































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