SIGINFO
Encyclopedia
On some Unix-like
platforms, SIGINFO is the signal
sent to computer program
s when a status request is received from the keyboard. The symbolic constant
for SIGINFO is defined in the header file
As SIGINFO is not defined by the POSIX
standard, its availability and meaning can vary from system to system. It is most commonly found on BSD-like operating systems.
On some versions of Linux, SIGINFO is defined as a synonym for SIGPWR
, however this is not consistent even between different Linux platforms, and most Linux systems do not define SIGINFO at all.
When the status key is typed on a tty, by default the kernel will print the current load average, active process on that tty and how much cpu it has used since launch.
A program may also catch the signal to print additional information, for example dd prints the number of bytes copied so far.
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
platforms, SIGINFO 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 computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
s when a status request is received from the keyboard. 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 SIGINFO 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. Symbolic signal names are used because signal numbers can vary across platforms.As SIGINFO is not defined by the 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...
standard, its availability and meaning can vary from system to system. It is most commonly found on BSD-like operating systems.
On some versions of Linux, SIGINFO is defined as a synonym for SIGPWR
SIGPWR
On some Unix-like platforms, SIGPWR is the signal sent to computer programs when the system experiences a power failure. The symbolic constant for SIGPWR is defined in the header file signal.h...
, however this is not consistent even between different Linux platforms, and most Linux systems do not define SIGINFO at all.
Usage
By default SIGINFO is mapped to the control-t key sequence on the keyboard. This can be changed via "stty status ..."When the status key is typed on a tty, by default the kernel will print the current load average, active process on that tty and how much cpu it has used since launch.
A program may also catch the signal to print additional information, for example dd prints the number of bytes copied so far.