Need signal handler that will rename core file.

[Rene' Seindal]

mcvic at prcrs.UUCP (David J. McVicar) writes:


> 	How can a process, while handling a core dumping signal, leave
> a core file in the current working directory (or other directory, if
> possible) that is not named 'core'.  It is often desirable to have a
> uniquely named core file, (ex. core.process.pid) for tracking problems and
> debugging executables in a production environment.  I have experimented with 
> signal handlers that will create a "dummy" core file in the current directory 
> when a signal is encountered, then set up a hard link to that core file using 
> the unique name.  But, upon process termination, our UNIX kernel (Ultrix 2.2) 
> will always create the "real" core using a different inode number than the 
> "dummy" core inode, resulting in a broken link with the unique name.

> 	The problem get's easier when you have a parent process that can
> come around after a child dies and rename it's childs core, but how can this
> be done in a process with no parent?

Here's a little function, that enables a process to dump core on the fly, and
continue execution afterwards.  It is for 4.3BSD, but it should be easy to
adapt it to another system.  Coredump are numbered core.1, core.2, ...

Not exactly what you asked for, but the idea might be useful.

Rene' Seindal (seindal at diku.dk).

------------------------------------------------------------------------
#include <signal.h>
#include <stdio.h>
#include <sys/wait.h>

#define COREFMT "core.%d"

int coredump()
{
    static int number = 0;
    char corename[100];		/* filename: core.number */
    register int pid, pid2;
    union wait status;

    number++;
    sprintf( corename, COREFMT, number );

    if ( (pid = vfork()) == 0 ) { /* Child */
	signal( SIGQUIT, SIG_DFL );
	kill( getpid(), SIGQUIT );
	sleep(1);		/* just for safetys sake */
	_exit(0);
    }
    if ( pid < 0 )		/* parent resumes after childs death */
	return -1;
    while( (pid2 = wait( &status )) > 0 && pid2 != pid )
	;
    if ( pid2 < 0 )		/* There were no dead children!! */
	return -1;
    if ( !status.w_coredump )	/* No coredump made */
	return -1;
    if ( rename( "core", corename ) < 0 )
	return -1;
    return number;
}
------------------------------------------------------------------------
.TH COREDUMP 3 LOCAL
.SH NAME
coredump \- make a coredump of the running process.
.SH SYNOPSIS
int coredump()
.SH DESCRIPTION 
.I coredump
will generate a coredump of the running process.
It attempts to 
.IR vfork (2)
and make the child dump core.  Core dumps are
numbered consecutivly, so 
.I coredump
can be called more than once.
.SH "RETURN VALUE"
.I coredump
returns -1 on failure, and the number of the core file if the core was
dumped succesfully.  Core files are numbered from 1 and up.
.SH BUGS
If your program has several children, and or uses SIGCHLD to wait for
them, it might break, since this routine forks and waits for the
child. 
.SH AUTHOR
Ren\'e Seindal, DIKU