GENWiki

PROFIL(3) Linux Programmer's Manual PROFIL(3)

NAME

     profil - execution time profile

SYNOPSIS

     #include <unistd.h>

     int profil(unsigned short *buf, size_t bufsiz,
                size_t offset, unsigned int scale);

 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

     profil():
         Since glibc 2.21:
             _DEFAULT_SOURCE
         In glibc 2.19 and 2.20:
             _DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
         Up to and including glibc 2.19:
             _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)

DESCRIPTION

     This  routine  provides  a means to find out in what areas your program
     spends most of its time.  The argument buf points to  bufsiz  bytes  of
     core.   Every  virtual 10 milliseconds, the user's program counter (PC)
     is examined: offset is subtracted and the result is multiplied by scale
     and divided by 65536.  If the resulting value is less than bufsiz, then
     the corresponding entry in buf is incremented.  If buf is NULL, profil-
     ing is disabled.

RETURN VALUE

     Zero is always returned.

ATTRIBUTES

     For   an   explanation   of   the  terms  used  in  this  section,  see
     attributes(7).

     +----------+---------------+-----------+
     |Interface | Attribute     | Value     |
     +----------+---------------+-----------+
     |profil()  | Thread safety | MT-Unsafe |
     +----------+---------------+-----------+

CONFORMING TO

     Similar to a call in SVr4 (but not POSIX.1).

BUGS

     profil() cannot be used on a program that also uses ITIMER_PROF  inter-
     val timers (see setitimer(2)).

     True  kernel  profiling  provides more accurate results.  Libc 4.4 con-
     tained a kernel patch providing a system call profil.