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Alphabetical listing for C

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core(4)
NAME
  core - Format of memory image file

SYNOPSIS
  #include <sys/core.h>

DESCRIPTION
  The system writes out a memory image of a terminated process when any of
  various errors occur. See sigaction(2) for the list of reasons; the most
  common are memory violations, illegal instructions, bus errors, and user-
  generated quit signals. The memory image is called core and is written in
  the process's working directory (provided that it can be; normal access
  controls apply).

  The maximum size of a core file is limited.  If a process exceeds this
  limit, any remaining data to be written to the core file is lost.

  Default behavior is for the system to create a file named core, overwriting
  any other file with that name in the working directory.

  You can enable enhanced core file naming, which causes the system to create
  unique names for core files. Core files are not overwritten, thereby
  preventing loss of valuable debugging information when the same program
  fails mulitiple times (and perhaps for mulitple reasons).

  When enhanced core file naming is enabled, the system produces core files
  with names in the following format:

  core.program_name.host_name.numeric_tag

  core
      The literal string core.

  program_name
      Up to sixteen characters taken from the program name as shown by the ps
      command.

  host_name
      The first portion of the system's network host name, or up to 16
      characters of the host name, taken from the part of the host name that
      precedes the first dot.

  numeric_tag
      This tag is assigned to the core file to make it unique among all of
      the core files generated by a program on a host. The maximum value for
      this tag, and thus the maximum number of core files for this program
      and host, is set by a system configuration parameter.

      Note the tag is not a literal version number. The system selects the
      first available unique tag for the core file. For example, if a
      program's core files have tags .0, .1, and .3, the system uses tag .2
      for the next core file it creates for that program.  If the system-
      configured limit for core file instances is reached, the system will
      not create any more core files for that program/host combination. By
      default, the system can create up to 16 versions of a core file.

      For example, the fourth core file generated on host buggy.net.ooze.com
      by the program dropsy would be:
	   core.dropsy.buggy.3

  Enhanced core file naming can be enabled at the system level or the program
  level:

  - At the system level, you can enable enhanced core file naming by setting
    the enhanced-core-name system configuration variable to 1 in the proc
    subsystem:
	 proc:
		 enhanced-core-name = 1

  - At the program level, you can enable enhanced core file naming by calling
    the uswitch system call with the USW_CORE flag set.	 See the EXAMPLE
    section.

  The system manager can limit the number of unique core file versions that a
  program can create on a specific host system by setting the system
  configuration variable enhanced-core-max-versions to the desired value:

       proc:
	       enhanced-core-name = 1
	       enhanced-core-max-versions = 8

  The miminum value is 1, the maximum is 99,999, and the default is 16.

EXAMPLE
  The following example shows a code fragment that calls the uswitch system
  call with the USW_CORE flag set:

       #include <signal.h>
       #include <sys/uswitch.h>

       /*
	* Request enhanced core file naming for
	* this process then create a core file.
	*/
       main()
       {
	       long uval = uswitch(USC_GET, 0);
	       uval = uswitch(USC_SET, uval | USW_CORE);
	       if (uval < 0) {
		      perror("uswitch");
		      exit(1);
	       }
	       raise(SIGQUIT);
       }

  In general, the debugger dbx(1) is sufficient to deal with core images.

RELATED INFORMATION
  sigaction(2), uswitch(2), sysconfigdb(8), dbx(1)

Index for Section 4

Alphabetical listing for C

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