---
name: alarm
status: documented
runtime: pp
source: src/runtime/pp/process.rs
---
```{index} single: alarm; Perl built-in (pp runtime)
```

# alarm

## Synopsis

```perl
my $remaining = alarm(30);   # fire SIGALRM in 30 seconds
alarm(0);                    # cancel any pending alarm
```

## Description

Schedules a `SIGALRM` signal to be delivered after a given number
of seconds.

Arranges for a `SIGALRM` to be delivered to the process after
the specified number of seconds.  If an alarm was already pending,
the old alarm is cancelled and the number of seconds that were
remaining is returned.  Calling `alarm(0)` cancels the current
alarm without setting a new one.

Commonly used with `eval`/`die` or `$SIG{ALRM}` to implement
timeouts:

```perl
eval {
    local $SIG{ALRM} = sub { die "timeout\n" };
    alarm(10);
    # ... long operation ...
    alarm(0);
};
```
Negative values are clamped to 0.

## See also

sleep, alarm, POSIX