SIGSYS
Encyclopedia
On POSIX
-compliant platforms, SIGSYS is the signal
sent to a process
when it passes a bad argument to a system call. The symbolic constant
for SIGSYS is defined in the header file
.
does not exist). POSIX.1 has this to say about SIGSYS:
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, SIGSYS 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 it passes a bad argument to a system call. 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 SIGSYS 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.hSignal.hsignal.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. SYS refers to a system callSystem call
In computing, a system call is how a program requests a service from an operating system's kernel. This may include hardware related services , creating and executing new processes, and communicating with integral kernel services...
.
Usage
Theoretically, in POSIX SIGSYS may be sent when a process supplies an incorrect argument to a system call. In practice, conforming implementations return ENOSYS if a code number does not correspond to a system call, or another error if a later argument is invalid (e.g. EBADF if a file descriptorFile descriptor
In computer programming, a file descriptor is an abstract indicator for accessing a file. The term is generally used in POSIX operating systems...
does not exist). POSIX.1 has this to say about SIGSYS:
- There is very little that a conforming POSIX.1 application can do by catching, ignoring or masking ... SIGSYS. ...
- One portable use that does exist ... is that a command interpreter can recognize them as the cause of a process's termination.