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PROFIL(2)		    BSD	System Calls Manual		     PROFIL(2)

NAME
     profil -- control process profiling

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     profil(char *samples, size_t size,	vm_offset_t offset, int	scale);

DESCRIPTION
     The profil() system call enables or disables program counter profiling of
     the current process.  If profiling	is enabled, then at every profiling
     clock tick, the kernel updates an appropriate count in the	samples	buf-
     fer.  The frequency of the	profiling clock	is recorded in the header in
     the profiling output file.

     The buffer	samples	contains size bytes and	is divided into	a series of
     16-bit bins.  Each	bin counts the number of times the program counter was
     in	a particular address range in the process when a profiling clock tick
     occurred while profiling was enabled.  For	a given	program	counter	ad-
     dress, the	number of the corresponding bin	is given by the	relation:

	   [(pc	- offset) / 2] * scale / 65536

     The offset	argument is the	lowest address at which	the kernel takes pro-
     gram counter samples.  The	scale argument ranges from 1 to	65536 and can
     be	used to	change the span	of the bins.  A	scale of 65536 maps each bin
     to	2 bytes	of address range; a scale of 32768 gives 4 bytes, 16384	gives
     8 bytes and so on.	 Intermediate values provide approximate intermediate
     ranges.  A	scale value of 0 disables profiling.

RETURN VALUES
     The profil() function returns the value 0 if successful; otherwise	the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

FILES
     /usr/lib/gcrt0.o  profiling C run-time startup file
     gmon.out	       conventional name for profiling output file

ERRORS
     The following error may be	reported:

     [EFAULT]		The buffer samples contains an invalid address.

SEE ALSO
     gprof(1)

HISTORY
     The profil() function appeared in Version 7 AT&T UNIX.

BUGS
     This routine should be named profile().

     The samples argument should really	be a vector of type unsigned short.

     The format	of the gmon.out	file is	undocumented.

BSD				 June 4, 1993				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | FILES | ERRORS | SEE ALSO | HISTORY | BUGS

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