On Windows, shell/[1,2]
executes the command using the CreateProcess() API and waits for the
command to terminate. If the command ends with a
& sign, the command is handed to the WinExec() API,
which does not wait for the new task to terminate. See also win_exec/2
and
win_shell/2.
Please note that the CreateProcess() API does not imply the
Windows command interpreter (cmd.exe and therefore commands that
are built in the command interpreter can only be activated using the
command interpreter. For example, a file can be compied using the
command below.
?- shell('cmd.exe /C copy file1.txt file2.txt').
Note that many of the operations that can be achieved using the shell
built-in commands can easily be achieved using Prolog primitives. See
make_directory/1, delete_file/1, rename_file/2,
etc. The clib package provides library(filesex),
implementing various high level file operations such as copy_file/2.
Using Prolog primitives instead of shell commands improves the
portability of your program.
The library library(process) provides process_create/3
and several related primitives that support more fine-grained
interaction with processes, including I/O redirection and management of
asynchronous processes.
shell(Command, 0)'./bin/sh; the
environment variable SHELL overrides this default. Not
available for Win32 platforms.SW_*
constants written in lowercase without the SW_*:
hide
maximize
minimize
restore
show
showdefault
showmaximized
showminimized
showminnoactive
showna
shownoactive
shownormal. In addition, iconic is a synonym
for minimize and
normal for shownormal.open, print
or explore or another operation registered with the shell
for the given document type. On modern systems it is also possible to
pass a URL as File, opening the
URL in Windows default browser. This call interfaces to the Win32 API
ShellExecute(). The Show argument determines the initial
state of the opened window (if any). See win_exec/2
for defined values.win_shell(Operation, File, normal)DWORD, the value is returned as an integer. If the value is
a string, it is returned as a Prolog atom. Other types are currently not
supported. The default `root' is HKEY_CURRENT_USER. Other
roots can be specified explicitly as HKEY_CLASSES_ROOT,
HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE or
HKEY_USERS. The example below fetches the extension to use
for Prolog files (see README.TXT on the Windows version):
?- win_registry_get_value(
'HKEY_LOCAL_MACHINE/Software/SWI/Prolog',
fileExtension,
Ext).
Ext = pl
CSIDL_
and mapping the constant to lowercase. Check the Windows documentation
for the function SHGetSpecialFolderPath() for a description of the
defined constants. This example extracts the `My Documents' folder:
?- win_folder(personal, MyDocuments). MyDocuments = 'C:/Documents and Settings/jan/My Documents'
all, collate, ctype, messages,
monetary, numeric or time. For
details, please consult the C library locale documentation. See also section
2.18.1. Please note that the locale is shared between all threads
and thread-safe usage of setlocale/3
is in general not possible. Do locale operations before starting threads
or thoroughly study threading aspects of locale support in your
environment before using in multi-threaded environments. Locale settings
are used by format_time/3, collation_key/2
and locale_sort/2.~--. Integer
arguments are passed as Prolog integers, float arguments and Prolog
floating point numbers and all other arguments as Prolog atoms. New
applications should use the Prolog flag argv.
See also the Prolog flag
argv.
A stand-alone program could use the following skeleton to handle command line arguments. See also section 2.10.2.4.
main :-
current_prolog_flag(argv, Argv),
append(_PrologArgs, [--|AppArgs], Argv), !,
main(AppArgs).
Representing time in a computer system is surprisingly complicated. There are a large number of time representations in use, and the correct choice depends on factors such as compactness, resolution and desired operations. Humans tend to think about time in hours, days, months, years or centuries. Physicists think about time in seconds. But, a month does not have a defined number of seconds. Even a day does not have a defined number of seconds as sometimes a leap-second is introduced to synchronise properly with our earth's rotation. At the same time, resolution demands a range from better than pico-seconds to millions of years. Finally, civilizations have a wide range of calendars. Although there exist libraries dealing with most if this complexity, our desire to keep Prolog clean and lean stops us from fully supporting these.
For human-oriented tasks, time can be broken into years, months, days, hours, minutes, seconds and a timezone. Physicists prefer to have time in an arithmetic type representing seconds or fraction thereof, so basic arithmetic deals with comparison and durations. An additional advantage of the physicist's approach is that it requires much less space. For these reasons, SWI-Prolog uses an arithmetic type as its prime time representation.
Many C libraries deal with time using fixed-point arithmetic, dealing with a large but finite time interval at constant resolution. In our opinion, using a floating point number is a more natural choice as we can use a natural unit and the interface does not need to be changed if a higher resolution is required in the future. Our unit of choice is the second as it is the scientific unit.86Using Julian days is a choice made by the Eclipse team. As conversion to dates is needed for a human readable notation of time and Julian days cannot deal naturally with leap seconds, we decided for the second as our unit. We have placed our origin at 1970-1-1T0:0:0Z for compatibility with the POSIX notion of time as well as with older time support provided by SWI-Prolog.
Where older versions of SWI-Prolog relied on the POSIX conversion functions, the current implementation uses libtai to realise conversion between time-stamps and calendar dates for a period of 10 million years.
We use the following time representations
-true if daylight saving time applies to the current
time, false if daylight saving time is relevant but not
effective, and -local to extract the local
time, 'UTC' to extract a UTC time or an integer describing
the seconds west of Greenwich.?- date_time_stamp(date(2006,7,214,0,0,0,0,-,-), Stamp), stamp_date_time(Stamp, D, 0), date_time_value(date, D, Date). Date = date(2007, 1, 30)
When computing a time stamp from a local time specification, the UTC offset (arg 7), TZ (arg 8) and DST (arg 9) argument may be left unbound and are unified with the proper information. The example below, executed in Amsterdam, illustrates this behaviour. On the 25th of March at 01:00, DST does not apply. At 02.00, the clock is advanced by one hour and thus both 02:00 and 03:00 represent the same time stamp.
1 ?- date_time_stamp(date(2012,3,25,1,0,0,UTCOff,TZ,DST),
Stamp).
UTCOff = -3600,
TZ = 'CET',
DST = false,
Stamp = 1332633600.0.
2 ?- date_time_stamp(date(2012,3,25,2,0,0,UTCOff,TZ,DST),
Stamp).
UTCOff = -7200,
TZ = 'CEST',
DST = true,
Stamp = 1332637200.0.
3 ?- date_time_stamp(date(2012,3,25,3,0,0,UTCOff,TZ,DST),
Stamp).
UTCOff = -7200,
TZ = 'CEST',
DST = true,
Stamp = 1332637200.0.
Note that DST and offset calculation are based on the POSIX function
mktime(). If mktime() returns an error, a representation_error
dst is generated.
| key | value |
year | Calendar year as an integer |
month | Calendar month as an integer 1..12 |
day | Calendar day as an integer 1..31 |
hour | Clock hour as an integer 0..23 |
minute | Clock minute as an integer 0..59 |
second | Clock second as a float 0.0..60.0 |
utc_offset | Offset to UTC in seconds (positive is west) |
time_zone | Name of timezone; fails if unknown |
daylight_saving | Bool daylight_savingtrue)
if dst is in effect |
date | Term date(Y,M,D) |
time | Term time(H,M,S) |
date(Y,M,D,H,M,S,O,TZ,DST) or a term date(Y,M,D).
aAbBcCdDeEff can be prefixed by an integer
to print the desired number of digits. E.g., %3f prints
milliseconds. This format is not covered by any standard, but available
with different format specifiers in various incarnations of the
strftime() function.
FgGVhHIjklmMnOpPrRsStTuUwWxXyYzZ+%The table below gives some format strings for popular time
representations. RFC1123 is used by HTTP. The full implementation of
http_timestamp/2
as available from library(http/http_header) is here.
http_timestamp(Time, Atom) :-
stamp_date_time(Time, Date, 'UTC'),
format_time(atom(Atom),
'%a, %d %b %Y %T GMT',
Date, posix).
| Standard | Format string |
| xsd | '%FT%T%:z' |
| ISO8601 | '%FT%T%z' |
| RFC822 | '%a, %d %b %Y %T %z' |
| RFC1123 | '%a, %d %b %Y %T GMT' |
posix, which
currently only modifies the behaviour of the a, A, b
and B format specifiers. The predicate is used to be able
to emit POSIX locale week and month names for emitting standardised
time-stamps such as RFC1123.parse_time(Text, _Format, Stamp). See parse_time/3.
| Name | Example |
| rfc_1123 | Fri, 08 Dec 2006 15:29:44 GMT |
| iso_8601 | 2006-12-08T17:29:44+02:00 |
| 20061208T172944+0200 | |
| 2006-12-08T15:29Z | |
| 2006-12-08 | |
| 20061208 | |
| 2006-12 | |
| 2006-W49-5 | |
| 2006-342 |
Date = date(Year,Month,Day).
Days of the week are numbered from one to seven: Monday = 1, Tuesday =
2, ... , Sunday = 7.
The Windows executable swipl-win.exe console has a number of predicates to control the appearance of the console. Being totally non-portable, we do not advise using it for your own application, but use XPCE or another portable GUI platform instead. We give the predicates for reference here.
win_window_title for
consistent naming.bottom, top, topmost and notopmost.
Topmost windows are displayed above all other windows.
true, show the window, if false hide the
window.
&
is underlined and defines the associated accelerator key. Before
is the label before which this one must be inserted. Using -
win_insert_menu('&Application', '&Help')
-