# Let a user ESCAPE from a loop without input control **URL:** \ **Category:** Forum\ **Tags:** Adabas-Natural, Natural, Natural-on-Linux\ **Created:** [July 25, 2011, 12:59pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797 "2011-07-25T12:59:28Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Stefan3](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/stefan3/32/245_2.png) [@Stefan3](https://techcommunity.softwareag.com/u/Stefan3)\ **Post date:** [July 25, 2011, 12:59pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/1 "2011-07-25T12:59:28Z")
Dear fellow Natural developers! 🙂 In many of my programs I use some kind of loop (e.g. READ, FOR) that processes lots of entries and takes some time (hours) to run. To let the user see the progress of the program I print out the current iteration like this: ```auto FOR #N 1 50000 SET CONTROL 'N' INPUT (AD=IO) #N END-FOR ``` However, if the user wants to abort the program it does not respond to his inputs due to SET CONTROL ‘N’: ```auto SET KEY PF3 FOR #N 1 50000 SET CONTROL 'N' INPUT (AD=IO) #N IF *PF-KEY EQ 'PF3' /* this does not work ESCAPE BOTTOM END-IF END-FOR ``` Is there 1. a way to abort such a loop according to the user’s input or 2. any other way of keeping the user informed about the progress of the loop that can be aborted? Best regards, Stefan ---
**Author:** ![Steve\_Robinson](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/steve_robinson/32/107_2.png) [@Steve\_Robinson](https://techcommunity.softwareag.com/u/Steve_Robinson)\ **Post date:** [July 25, 2011, 4:21pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/2 "2011-07-25T16:21:20Z")
The problem, of course, is that you want to use SET CONTROL ‘N’ to apprise the user of what is happening, and this does not allow for interaction with the user. If you add an INPUT without SET CONTROL ‘N’, you permit the user to interact, but you slow things down ( the user, of course, will be the slowest part of the processing). The following code is as close as I think you will get to satisfying both of your requirements: define data local 1 #loop (n8) 1 redefine #loop 2 filler 4x 2 #ten-thousand (a1) 2 #one-thousand (a1) 1 #end (a1) 1 #delay (i2) init \<1\> end-define \* for #loop = 1 to 100000 perform break processing - check for a thousands break at break of #one-thousand call ‘cmroll’ #delay set control ‘n’ input 'up to iteration: ’ #loop (ad=o) end-break - now check if a ten thousand break at break of #ten-thousand input ‘do you wish to end processing? Y or N ==\>’ #end if #end = ‘Y’ stop end-if end-break end-for - end The CALL CMROLL is just to slow things down so you can see what is happening. If you remove it, the up tp iteration message will be just a blur. Of course, you would have to set the conditions for the two breaks. If you were reading through a file in logical sequence, by name, you might use the first letter of the name to control the second input and a counter within that break to control the first break. Lots of variations of the code are possible, BUT, as noted above, you will have to establish the conditions for the two breaks. steve ---
**Author:** ![Stefan3](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/stefan3/32/245_2.png) [@Stefan3](https://techcommunity.softwareag.com/u/Stefan3)\ **Post date:** [July 26, 2011, 1:51pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/3 "2011-07-26T13:51:11Z")
Dear Steve, your solution does not work for me, because under normal circumstances the loop should run through without any user interaction at all (think of a program that runs really long, e.g. 40h like mine: nobody can sit in front of it that long). Only if the user spontaneously decides he wants to abort it (e.g. because he found a bug) it should be stopped. What I’ve done before is to stow the program while it’s running or simply to close its session, but that leads to a hard abort without any possibility to clean up (e.g. close work files, end transactions). I’ve come up with this solution (and it’s working fine for me), but I still would like to know if there is any other way to do this. Function ABORT ```auto DEFINE FUNCTION ABORT RETURNS (L) ABORT := FALSE END-FUNCTION END ``` Loop ```auto F1. FOR... IF ABORT(<>) PERFORM CLEAN-UP ESCAPE BOTTOM (F1.) END-IF /* normal loop processing END-FOR ``` Now I can change the return value of ABORT to TRUE and stow the function during the loop’s runtine and have it abort cleanly. However, there are two tradeoffs with this approach: 1. the overhead of calling ABORT in every loop iteration 2. a normal user without access to the source code can still not abort the program Best regards, Stefan ---
**Author:** ![system](https://global.discourse-cdn.com/techcommunity/original/3X/c/d/cd19967bb605d28a72d77eb83a1cae22f3df2eb8.svg) [@system](https://techcommunity.softwareag.com/u/system)\ **Post date:** [July 26, 2011, 2:22pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/4 "2011-07-26T14:22:45Z")
Hi Stefan, 1. You could do the IF ABORT only for the e.g. 10k iteration. This would limit the overhead. ---
**Author:** ![Steve\_Robinson](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/steve_robinson/32/107_2.png) [@Steve\_Robinson](https://techcommunity.softwareag.com/u/Steve_Robinson)\ **Post date:** [July 26, 2011, 4:43pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/5 "2011-07-26T16:43:57Z")
Hi Stefan; Instead of your current approach (which requires access to source code), How about having an external file? The user would have the responsibility to alter a value in what would be a work file. This could be combined with Mogens idea of a counter controlling when to test for abort. steve ---
**Author:** ![system](https://global.discourse-cdn.com/techcommunity/original/3X/c/d/cd19967bb605d28a72d77eb83a1cae22f3df2eb8.svg) [@system](https://techcommunity.softwareag.com/u/system)\ **Post date:** [July 26, 2011, 5:46pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/6 "2011-07-26T17:46:47Z")
Hi Stefan, Perhaps the attention key (on unix I believe it is CTRL+C) can interrupt your program. On mf there must be an Adabas call in the loop to stop it. I do not have a unix available so I cannot test. ---
**Author:** ![Stefan3](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/stefan3/32/245_2.png) [@Stefan3](https://techcommunity.softwareag.com/u/Stefan3)\ **Post date:** [July 27, 2011, 1:41pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/7 "2011-07-27T13:41:55Z")
Hi Steve. > [@Steve Robinson](#): > > How about having an external file? This could be combined with Mogens idea of a counter controlling when to test for abort. Yes, that would be a possibility. The overhead for reading the file could be compensated by only doing it evey nth iteration. Thanks for the idea. Although I would rather find a more “natural” way for the user to abort the program. I think I’ll take a closer look at what Morgens wrote: > [@Morgens](#): > > Perhaps the attention key (on unix I believe it is CTRL+C) can interrupt your program. Best regards, Stefan ---
**Author:** ![Stefan3](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/stefan3/32/245_2.png) [@Stefan3](https://techcommunity.softwareag.com/u/Stefan3)\ **Post date:** [July 27, 2011, 3:14pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/8 "2011-07-27T15:14:37Z")
Mh… does anyone know how to enter attention keys in linux? What are the default key combinations used for them? CTRL-C and all the other usual suspects don’t seem to work (not recognized by \*PF-KEY). I’ve tried it using our own terminal emulation and PuTTY. Best regards, Stefan ---
**Author:** ![system](https://global.discourse-cdn.com/techcommunity/original/3X/c/d/cd19967bb605d28a72d77eb83a1cae22f3df2eb8.svg) [@system](https://techcommunity.softwareag.com/u/system)\ **Post date:** [April 2, 2021, 3:00pm UTC](https://techcommunity.softwareag.com/t/let-a-user-escape-from-a-loop-without-input-control/97797/9 "2021-04-02T15:00:38Z")