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 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.

[edit] Etymology

SIG 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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