- Reference manual
- SWI-Prolog C-library
- library(process): Create processes and redirect I/O
- library(filesex): Extended operations on files
- library(uid): User and group management on Unix systems
- library(syslog): Unix syslog interface
- library(socket): Network socket (TCP and UDP) library
- The stream_pool library
- library(uri): Process URIs
- CGI Support library
- Password encryption library
- library(uuid): Universally Unique Identifier (UUID) Library
- SHA* Secure Hash Algorithms
- library(md5): MD5 hashes
- library(hash_stream): Maintain a hash on a stream
- Memory files
- Time and alarm library
- library(unix): Unix specific operations
- Limiting process resources
- library(udp_broadcast): A UDP broadcast proxy
- library(prolog_stream): A stream with Prolog callbacks
- SWI-Prolog C-library
library(time) provides timing and alarm functions.
Alarms are thread-specific, i.e., creating an alarm causes the alarm
goal to be called in the thread that created it. The predicate current_alarm/4
only reports alarms that are related to the calling thread. If a thread
terminates, all remaining alarms are silently removed. Most applications
- alarm(+Time, :Callable, -Id, +Options)
- Schedule Callable to be called Time seconds from
Time is a number (integer or float). Callable is
called on the next pass through a call- or redo-port of the Prolog
engine, or a call to the PL_handle_signals() routine from
SWI-Prolog. Id is unified with a reference to the timer.
The resolution of the alarm depends on the underlying implementation, which is based on pthread_cond_timedwait() (on Windows on the pthread emulation thereof). Long-running foreign predicates that do not call PL_handle_signals() may further delay the alarm. The relation to blocking system calls (sleep, reading from slow devices, etc.) is undefined and varies between implementations.
Options is a list of
Name(Value)terms. Defined options are:
- alarm(+Time, :Callable, -Id)
- Same as
alarm(Time, Callable, Id,).
- alarm_at(+Time, :Callable, -Id, +Options)
- as alarm/3, but Time is the specification of an absolute point in time. Absolute times are specified in seconds after the Jan 1, 1970 epoch. See also date_time_stamp/2.
- Activate an alarm allocated using alarm/4
with the option
install(false)or stopped using uninstall_alarm/1.
- install_alarm(+Id, +Time)
- As install_alarm/1, but specifies a new (relative) timeout value.
- Deactivate a running alarm, but do not invalidate the alarm identifier. Later, the alarm can be reactivated using either install_alarm/1 or install_alarm/2. Reinstalled using install_alarm/1, it will fire at the originally scheduled time. Reinstalled using install_alarm/2 causes the alarm to fire at the specified time from now.
- Remove an alarm. If it is not yet fired, it will not be fired any more.
- current_alarm(?At, ?:Callable, ?Id, ?Status)
- Enumerate the not-yet-removed alarms. Status is one of
doneif the alarm has been called,
nextif it is the next to be fired and scheduled otherwise.
- call_with_time_limit(+Time, :Goal)
- True if Goal completes within Time seconds. Goal
is executed as in once/1.
If Goal doesn't complete within Time seconds (wall
time), exit using the exception
time_limit_exceeded. See catch/3.
Please note that this predicate uses alarm/4 and therefore its effect on long-running foreign code and system calls is undefined. Blocking I/O can be handled using the timeout option of set_stream/2 or waiting for input using wait_for_input/3.