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PRCTL(2)			    Linux Programmer's Manual				 PRCTL(2)

       prctl - operations on a process

       #include <sys/prctl.h>

       int  prctl(int  option,	unsigned  long	arg2,  unsigned  long  arg3 , unsigned long arg4,
       unsigned long arg5);

       prctl is called with a first argument describing  what  to  do  (with  values  defined  in
       <linux/prctl.h>),  and  further parameters with a significance depending on the first one.
       The first argument can be:

	      (since Linux 2.1.57) Set the parent process death signal of the current process  to
	      arg2  (either  a	signal value in the range 1..maxsig, or 0 to clear).  This is the
	      signal that the current process will get	when  its  parent  dies.  This	value  is
	      cleared upon a fork().

	      (since Linux 2.3.15) Read the current value of the parent process death signal into
	      the (int *) arg2.

	      (Since Linux 2.4) Set the state of the flag determining whether core dumps are pro-
	      duced for this process upon delivery of a signal whose default behaviour is to pro-
	      duce a core dump.  (Normally this flag is set for a process by default, but  it  is
	      cleared  when  a	set-UID or set-GID program is executed and also by various system
	      calls that manipulate process UIDs and GIDs).  arg2 must be either  0  (process  is
	      not dumapable) or 1 (process is dumpable).

	      (Since  Linux 2.4) Return (as the function result) the current state of the calling
	      process's dumpable flag.

	      Set the state of the process's "keep capabilities" flag, which  determines  whether
	      the  process's effective and permitted capability sets are cleared when a change is
	      made to the process's user IDs such that all of the process's real, effective,  and
	      saved  set  user	IDs  become non-zero when at least one of them previously had the
	      value 0.	(By default, these credential sets are cleared).  arg2 must be	either	0
	      (capabilities are cleared) or 1 (capabilities are kept).

	      Return  (as  the	function result) the current state of the calling process's "keep
	      capabilities" flag.

       PR_GET_DUMPABLE and PR_GET_KEEPCAPS return 0 or 1 on success.   All  other  option  values
       return 0 on success.  On error, -1 is returned, and errno is set appropriately.

       EINVAL The  value  of  option is not recognized, or it is PR_SET_PDEATHSIG and arg2 is not
	      zero or a signal number.

       This call is Linux-specific.  IRIX has a prctl  system  call  (also  introduced	in  Linux
       2.1.44 as irix_prctl on the MIPS architecture), with prototype

       ptrdiff_t prctl(int option, int arg2, int arg3);

       and  options  to  get  the maximum number of processes per user, get the maximum number of
       processors the calling process can use, find out whether a specified process is	currently
       blocked, get or set the maximum stack size, etc., etc.

       The  prctl()  systemcall was introduced in Linux 2.1.57.  There is no prctl() library call
       as yet.


Linux 2.4.18				    2002-06-27					 PRCTL(2)
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