SIGPROF
Encyclopedia
On POSIX
POSIX
POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...

-compliant platforms, SIGPROF is the signal
Signal (computing)
A signal is a limited form of inter-process communication used in Unix, Unix-like, and other POSIX-compliant operating systems. Essentially it is an asynchronous notification sent to a process in order to notify it of an event that occurred. When a signal is sent to a process, the operating system...

 sent to a process
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...

 when the profiling timer expires. The symbolic constant
C preprocessor
The C preprocessor is the preprocessor for the C and C++ computer programming languages. The preprocessor handles directives for source file inclusion , macro definitions , and conditional inclusion ....

 for SIGPROF is defined in the header file
Header file
Some programming languages use header files. These files allow programmers to separate certain elements of a program's source code into reusable files. Header files commonly contain forward declarations of classes, subroutines, variables, and other identifiers...

 signal.h
Signal.h
signal.h is a header file defined in the C Standard Library to specify how a program handles signals while it executes. A signal can report some exceptional behavior within the program , or a signal can report some asynchronous event outside the program .A signal can be generated...

. Symbolic signal names are used because signal numbers can vary across platforms.

Etymology

SIG is a common prefix for signal names. PROF is an abbreviation
Abbreviation
An abbreviation is a shortened form of a word or phrase. Usually, but not always, it consists of a letter or group of letters taken from the word or phrase...

 for profiler.

Usage

SIGPROF is sent when a timer expires, like SIGVTALRM
SIGVTALRM
On POSIX-compliant platforms, SIGVTALRM is the signal sent to a process when a time limit has elapsed. In source code, SIGVTALRM is a symbolic constant defined in the header file signal.h. Symbolic signal names are used because signal numbers can vary across platforms.-Etymology:SIG is a common...

 and the more popular SIGALRM
SIGALRM
On POSIX-compliant platforms, SIGALRM is the signal sent to a process when a time limit has elapsed. The symbolic constant for SIGALRM is defined in the signal.h header file. Symbolic signal names are used because signal numbers can vary across platforms....

. The distinction of SIGPROF is that its timer counts time spent executing the process and by the system carrying out tasks on behalf of the process; SIGVTALRM measures only time spent by the process itself, while SIGALRM measures real time. It is suggested that SIGPROF be used with SIGVTALRM to profile the time spent by the process in user and kernel space.
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