SIGALRM

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SIGALRM
Description Alarm clock
Default action Abnormal termination of the process
SA_SIGINFO macros
None

On POSIX-compliant platforms, SIGALRM is the signal thrown by computer programs 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.

[edit] Etymology

SIGs is a common prefix for signal names. ALRM stands for alarm.

[edit] Usage

Computer programs often use SIGALRM to make a long-running action time out, or to provide a way of performing an action at regular intervals.

SIGALRM is generally raised a whole number of seconds after an alarm system call is made. It is sometimes used to implement the sleep function; consequently, programs cannot reliably use alarm to "wake up" from a delay caused by sleep [1].

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Computing signals
POSIX
SIGABRT · SIGALRM · SIGFPE · SIGHUP · SIGILL · SIGINT · SIGKILL · SIGPIPE · SIGQUIT · SIGSEGV · SIGTERM · SIGUSR1 · SIGUSR2 · SIGCHLD · SIGCONT · SIGSTOP · SIGTSTP · SIGTTIN · SIGTTOU · SIGBUS · SIGPOLL · SIGPROF · SIGSYS · SIGTRAP · SIGURG · SIGVTALRM · SIGXCPU · SIGXFSZ · Realtime signals are user definable (SIGRTMIN+n through SIGRTMAX)
non-POSIX