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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, u_long offset, u_int scale);

DESCRIPTION
     The profil() function enables or disables program counter profiling of the current process.  If profil-ing profiling
     ing is enabled, then at every clock tick, the kernel updates an appropriate count in the samples
     buffer.

     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 clock
     tick occurred while profiling was enabled.  For a given program counter address, the number of the cor-responding corresponding
     responding bin is given by the relation:

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

     The offset parameter is the lowest address at which the kernel takes program counter samples.  The
     scale parameter 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
     If the scale value is nonzero and the buffer samples contains an illegal address, profil() returns -1,
     profiling is terminated and errno is set appropriately.  Otherwise profil() returns 0.

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