What's the best way to do the semantic equivalent of the traditional sleep() system call from within an Informix SPL routine? In other words, simply "pause" for N seconds (or milliseconds or whatever, but seconds are fine). I'm looking for a solution that does not involve linking some new (perhaps written by me) C code or other library into the Informix server. This has to be something I can do purely from SPL. A solution for IDS 10 or 11 would be fine.
#RET - The "obvious" answer wasn't obvious to me! I didn't know about the SYSTEM command. Thank you! (And yes, I'm the guy you think I am.)
Yes, it's for debugging purposes only. Unfortunately, CURRENT within an SPL will always return the same value, set at the entry to the call:
"any call to CURRENT from inside the SPL function that an EXECUTE FUNCTION (or EXECUTE PROCEDURE) statement invokes returns the value of the system clock when the SPL function starts."
—IBM Informix Guide to SQL
Wrapping CURRENT in its own subroutine does not help. You do get a different answer on the first call to your wrapper (provided you're using YEAR TO FRACTION(5) or some other type with high enough resolution to show the the difference) but then you get that same value back on every single subsequent call, which ensures that any sort of loop will never terminate.
There must be some good reason you're not wanting the obvious answer:
SYSTEM "sleep 5". If all you're wanting is for the SPL to pause while you check various values etc, here are a couple of thoughts (all of which are utter hacks, of course):
Make the TRACE FILE a named pipe (assuming Unix back-end), so it blocks until you choose to read from it, or
Create another table that your SPL polls for a particular entry from a WHILE loop, and insert said row from elsewhere (horribly inefficient)
Make SET LOCK MODE your friend: execute "SET LOCK MODE TO WAIT n" and deliberately requery a table you're already holding a cursor open on. You'll need to wrap this in an EXCEPTION handler, of course.
Hope that is some help (and if you're the same JS of Ars and Rose::DB fame, it's the least I could do ;-)
I'm aware that the answer is too late. However I've recently encountered the same problem and this site shows as the first one. So it is beneficial for other people to place new anwser here.
Perfect solution was found by Eric Herber and published in April 2012 here: How to sleep (or yield) for a fixed time in a stored procedure
Unfortunately this site is down.
His solution is to use following function:
integer sysadmin:yieldn( integer nseconds )
I assume that you want this "pause" for debugging purposes, otherwise think about it, you'll always have some better tasks to do for your server than sleep ...
A suggestion: Maybe you could get CURRENT, add it a few seconds ( let mytimestamp ) then in a while loop select CURRENT while CURRENT <= mytimestamp . I've no informix setup around my desk to try it, so you'll have to figure the correct syntax. Again, do not put such a hack on a production server. You've been warned :D
Then you'll have to warp CURRENT in another function that you'll call from the first (but this is a hack on the previous hack ...).
Related
Context
So I finally give a try to Fish, and as one would expect I encounter some frictions due to differences with my usual routines.
The most astonishing for me, as for many other, was the absence of the bang operator. I'm fine with the lose of sudo !!, as the suggested function replacement seems even better to me, I named it gar which means "To make, compel (someone to do something); to cause (something to be done." However I'll need a replacement for !<abc><enter> which grab the last history line starting with <abc> and run it without further ado, suggestions are welcome.
Now, for the more personal things:
- I use a Typematrix 2030 keyboard
- I use a bépo layout
- I like to configure default finger position keys with the most used actions
Aims
As on my keybord <enter> is well positioned and is semantically relevant for that, ideally I would like to achieve the following key binding:
ctrl-enter: accept the whole suggestion and run it without further confirmation
ctrl-tab: accept the whole suggestion and wait for further edit
alt-enter: redo the last command without further confirmation
But according to xev it appears that, at least with Gnome-terminal, this combinations are not recognized. Are they terminal that supports it? For now I remapped these three to <ctrl>-i, <alt>-i and <alt>-I respectively:
bind --preset \ci forward-char execute
bind --preset \ei forward-char
bind --preset \eI forward-word
This works as expected, but it seems that now the tab key will also map to the first item. I guess that tab map to <alt>-i at some point in the shell stack. I wasn't aware of that, so I don't know yet if it will be possible for Fish to separate each of them.
To manage jobs, I also came with
bind --preset \es fg
bind --preset \eS bg
The first works as expected, but the second one doesn't. With application like vim, the binding should be operated in the application configuration itself of course. But for things as trivial as yes, <alt>-S won't work as expected while <crl>-z continue to operate normally.
I also would like to bind some commands like ls -alh and git status --short to a directly executed command, showing the result bellow the currently edited line, allowing to further type seamlessly, but didn't find the way to do it yet.
Summary of remaining question
So here are my more precise questions summarised:
how do I bind the sleep signal to <alt>-S?
is there a terminal I can use where <alt>-<enter> and <ctrl>-<enter> works?
how to seamlessly run command while maintaining the current line edition in place?
can you bind something to <alt>-i without altering <tab>?
how do I bind the sleep signal to -S?
What you are doing with bind \es fg is to alter a binding inside the shell.
But when you execute yes, the shell isn't currently in the foreground, so shell bindings don't apply.
What you'd have to do instead is change the terminal settings via stty susp \cs,
but fish resets the terminal settings when executing commands (so you can't accidentally break them and end up in an unusable environment), so there currently is no way to do this in fish.
can you bind something to <alt>-i without altering <tab>?
Sure. You bind \ei. Which is escape+i, which is alt-i (because in a terminal alt is escape).
Your problem is with ctrl-i, which in the way terminals encode control+character is tab. The application receives an actual tab character, and at that point the information has been lost.
is there a terminal I can use where - and - works?
Most terminals should send \e\r for alt-enter. ctrl-enter again is unencodable with the usual code (because \r is ctrl-m), just like ctrl-tab is.
Any fix to this requires the terminal to encode these combination differently.
how to seamlessly run command while maintaining the current line edition in place?
I don't know what you mean by this. I'm guessing you want fish to remain open and editable while a command also runs in the foreground. That can't work. There's no way to synchronize output from two commands to a terminal, not with cursor movement being what it is.
I'm currently working on a lua program.
I want to use it in Minecraft with a mod called "OpenComputers" which allows the use of lua scripts on emulated systems.
The programm I'm working on is relatively simple: you have a console and you enter a command to control a machine.
It looks like this:
while(true) do
io.write("Enter command\n>")
cmd = io.read()
-- running code to process the command
end
But the problem is: I need a routine running in the background which checks data given by the machine.
while(true) do
-- checking and reacting
end
How can I make this work?
I can't jump to a coroutine while waiting on io.read()
It's not enough to check after someone used a command (sometimes I don't use it for days but I still have to keep an eye on it)
I'm relatively new to lua so please try to give a simple solution and - if possible - one that does not rely on third party tools.
Thank you :)
If you have some experience with opencomputers, you can add a(n asynchronous) listener for "key_down", and store the user input in a string (or whatever you want).
For example:
local userstr = ""
function keyPressed(event_name, player_uuid, ascii)
local c = string.char(ascii)
if c=='\n' then
print(userstr)
userstr = ""
else
userstr=userstr..c
end
--stores keys typed by user and prints them as a string when you press enter
end
event.register("key_down", keyPressed)
Running multiple tasks is a very broad problem solved by the operating system, not something as simple as Lua interpreter. It is solved on a level much deeper than io.read and deals with troubles numerous enough to fill a couple of books. For lua vm instead of physical computer, it may be simpler but it would still need delving deep into how the letters of code are turned into operations performed by the computer.
That mod of yours seems to already emulate os functionality for you: 1,2. I believe you'll be better off by making use of the provided functionality.
Is it possible to abend your job intentionally through COBOL program.
suppose I have an Input file having Header,Detail and Trailer records. I will write a COBOL pgm which reads this file.If no Detail records are found in this file then I want to abend my job by giving some Abend Message and some Abend Code.Is it Possible?
Do you want to ABEND your program or just set a RETURN-CODE?
I suspect setting a RETURN-CODE, writing a message
and then terminating the program via a STOP RUN or GOBACK is all that
you really want to do. Causing an actual ABEND may not be necessary.
In an IBM batch environment, the RETURN-CODE set by your program becomes the
RC for the JCL job step the program was run under. This is typically what you
want to set and test for.
The RETURN-CODE is set by MOVEing a numeric value to it. For example:
DISPLAY 'No Detail Records found in file.'
MOVE 16 TO RETURN-CODE
GOBACK.
You may also issue a program dump from a program run under Language Environment (IBM
Mainframe option) using
the CEE3DMP--Generate dump
utility.
In older IBM Mainframe COBOL programs, you might see calls to the ILBOABN0 routine. This call
abended your program and issued a dump. This routine is now depreciated in favour of the
technique outlined above.
Finally, really old programs might have code in them to generate abends. This can be done in any number of ways, but division by zero was
often a favourite:
DIVIDE SOME-NUMBER BY ZERO GIVING SOME-NUMBER.
Works every time!
Personally, I recommend setting the RETURN-CODE over calling ILBOABN0 or data-exception tehcniques.
Note: The RETURN-CODE special-register is not part of the COBOL-85 standard. It is available as an IBM extention to the language. You may need to resort to a different mechanism if you are working in a non-IBM compatible environment.
see the following link on how to set the return code passed back to a JCL job step as well as force an Abened code.
http://www.tek-tips.com/viewthread.cfm?qid=1058302&page=22
First, you should check what is accepted by your own shop's/site's working standards. Most teams will already have an accepted way to deliberately abend a program for a 'logic' reason. One company I worked at has a very simple program called SYSABND2, which I believe is written in assembler, which is called just to abend the program.
That said, to ABEND (not just set return code), you should call module CEE3ABD (or previous version ILBOABN0, which is now deprecated).
For details, see:
https://www.ibm.com/support/knowledgecenter/SSLTBW_2.4.0/com.ibm.zos.v2r4.ceea300/clcdump.htm
http://publib.boulder.ibm.com/infocenter/zvm/v5r4/index.jsp?topic=/com.ibm.zos.r9.ceea400/ceea4150320.htm
One method for doing an abnormal end of run is to output a message to the user terminal or to the operator at a mainframe computer centre and possibly to a printer if necessary, all depending on the type of computer the program is to be run on. In cobol it is possible to use DISPLAY UPON .. and use an identifier for the terminal, operator console, or printer as defined in an entry in the SPECIAL-NAMES section of the ENVIRONMENT DIVISION. An example may be similar to this using the correct device names for your case
OPERATOR-CONSOLE IS OUT-OP2 in special-names with DISPLAY "RUN ERROR - NO DETAIL RECORDS, ABORTING" UPON OUT-OP2 and
DISPLAY "REPORT TO OPERATIONS MANAGER" UPON OUT-OP2 and STOP RUN. in procedure division.
A reference to the circumstance would need to be included in any job or macro and operating instructions.
Yes, it is possible to abend your job intentionally through COBOL program by simply calling one module which doesn't exist. It will give S806 abend code.
I have rewritten a VB6 application in Delphi. It should have only one instance running. How can I do this with minimum of code?
In VB6 we just have to use one single line of code
>
If App.PrevInstance Then
'Take some action
End If
On goggling I did find a solution but it is very length and we have to mess with .drp file.
I do not want to do that.
I want something simpler.
I have some code along the lines of:
var
AppMutex: THandle;
{ .... }
initialization
// Create the mutex
AppMutex := CreateMutex(nil, True, 'MY-APPLICATION-NAME');
if (AppMutex = 0) or (GetLastError = ERROR_ALREADY_EXISTS) then
begin
MessageDlg('My application is already running on this computer.'#13#10+
'You should close the other instance before starting a new one.',mtError,
[mbOK],0);
Halt;
end;
finalization
// Close the mutex
CloseHandle(AppMutex);
but I'm sure the answers in the thread that #mghie linked to are more helpful/richer features!
Edit: Note you can make this into a small unit in it's own right, then just use that unit in your project(s).
Note that in many cases, the user's expecation will be that launching the second instance results in the first instance being restored and brought to the foreground. Don't expect users to understand the difference between restoring a minimized/hidden app and launching from a shortcut or start menu.
In my experience one cannot decide in general wether an application my be started twice or not. It may be for instance perfectly valid to start the same application if it is started in another folder or under another user account or whatever. On the other hand it might be the case that two different applications may not run together if they are started in the same folder or so.
So besides the different approaches with mutexes and semaphores and handling race conditions, it is the wise selection of the mutex's or semaphore's name that handles the above combinations appropriately.
If an application may not run twice at all, take a GUID like name. You can even use the exe's filename if you can ignore that someone might rename it.
Restricting the one-time-start on a specific folder, you can take the exe path into account, but be aware that due to mappings different pathes may end up at the same exe.
Finding dead code in Delphi is usually real simple: just compile and then scan for routines missing their blue dots. The smart linker's very good about tracking them down, most of the time.
Problem is, this doesn't work for event handlers because they're published methods, which (theoretically) could be invoked via RTTI somehow, even though this almost never happens in actual practice.
I'm trying to clean up a large VCL form unit that's been bent, folded, spindled and mutilated various times throughout its history. It would sure be nice if I had some way to find event handlers that aren't actually referenced by the form's DFM and delete them. Is there any easy way to do this? A plug-in IDE Expert, for example?
This is a bit ugly (OK, it's a lot ugly), but for one unit it's close to foolproof, and requires no additional tools:
Make sure that the current version of the form is checked into source control!
Go to the top of the interface of the class where the event handlers are. Delete all of the event handler method interfaces.
Look at Code Explorer/Error Insight. The methods which have implementations but no interfaces will be highlighted. Delete the implementations.
Now save the unit. Delphi will, one at a time, complained about the missing event handler for each event that is actually handled. Write these down as the errors come up.
Check out the original version of the form, and remove the event handlers for anything not on your list.
Use the "Rename Method" refactoring to rename each event handler. Check the "View references before refactoring" checkbox.
Check the Refactoring window. If the event handler is linked to a control, there will be a "VCL Designer Updates" section show which control(s) are linked to the method.
This will also show if the method is called from any other units, or is assigned programmatically.
Note: this is for D2006, may be slightly different in later versions.
ModelMaker Code Explorer contains an so-called Event handler view. It also shows event handlers not connected to any component.
I dont think this is possible from an automatic point of view. event handlers are activated when a particular event occurs inside an object. That the even is not triggered in a given run doesnt mean that there isnt an execution pathway to lead to it.
also you can assign handlers dynamically at runtime so whats used in one situation is not garuanteed.
e.g.
button.onclick := DefaultClickHandler;
button.onClick := SpecialClickHandler;
Assuming that the click handlers match the onclick event signature, but you wouldnt get a compile if the signature was incorrect.
however, you can probably find all the abandoned handlers by looking for all the methods that find have a (Sender: TObject) method signature and comparing that his of methods to those in the .dfm (make sure you save it as text if you are working with an older version of delphi), antyhing not wired up automatically would be suspect in my book.
--
if you dont want to go down the cygwin path, you can load the src and dfm into two TStirngLists and rip out the name/idents from each and generate a list with a couple of loops and some string manipulations. my guess is about 20 minutes of work to get something you can live with .
There is no solution that is guaranteed to give a correct answer in the most general case (based, as you note, on the possibility of calling them via RTTI).
One solution would be to do code coverage tests and look carefully at handlers that were never reached.
I'm not aware of a preexisting app or plugin to do this, but it shouldn't be hard to script.
Assuming you're not using RTTI or manually assigning event handlers: (I'm a C++Builder user rather than Delphi, so the following may not be quite correct.)
Make a list of all published methods in your code.
The proper way to do this is to read *.pas. Find each text block that starts with a class declaration or a published directive and ends with a end, private, or public. Within each of these text blocks, extract each procedure.
The easy way to do this is to make a list of common event handler types and assume they're published.
Once you have this list, print everything from the list that's not found in your DFM file.
I'm most comfortable using Cygwin or Linux tools for scripting. Here's a bash script that works in Cygwin and should do what you want.
#!/bin/bash
for file in `find -name *.pas`; do
echo $file:
# Get a list of common event handling procedures.
# Add more types between the | symbols.
egrep '^[[:space:]]+procedure.*(Click|FormCreate|FormClose|Change|Execute)\(' $file |
awk '{print $2}' | cut -f 1 -d '(' > published.txt
# Get a list of used event procedures.
egrep '^[[:space:]]+On.* =' ${file%.pas}.dfm | awk '{print $3}' > used.txt
# Compare the two.
# Files listed in the left column are published but not used, so you can delete them.
# Files in the right column were not by our crude search for published event
# handlers, so you can update the first egrep command to find them.
comm -3 published.txt used.txt
echo
done
# Clean up.
rm published.txt used.txt
To actually use this, if you're not familiar with Cygwin:
Download and install Cygwin. I think the default install should give you all of the tools I used, but I'm not positive.
Save the script to your source directory as cleanup.sh.
Start a Cygwin command prompt.
If your source is in c:\MyApp, then type cd /cygdrive/c/myapp
Type ./cleanup.sh and press Enter.
There's a much easier approach than Craig's.
Go to a suspect event handler. Rename it in a consistent way--I do this by putting an x in front of the name, go down to the implementation and do the same thing. See what the compiler thinks of it.
If it's not happy you just change the names back.
You can use the same approach to eliminate data elements that no longer do anything.