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тАО06-04-2010 01:17 AM
тАО06-04-2010 01:17 AM
ksh limits - Max # of Env Variables and Contents
And the apps crew are complaining they're unable to at a certain point.
ulimit is set to:
opsuser@SRV001> ulimit -a
time(seconds) unlimited
file(blocks) unlimited
data(kbytes) 3145728
stack(kbytes) 376832
memory(kbytes) unlimited
coredump(blocks) 4194303
I am thinking of bumping of kernel param to the 32bit maxdsiz value of 4GB.
But is there a limit to the above? Accdg to our apps crew, this new environment is more than twice as big as the previous where they have around ~2000 environment variables declared @ maxdsiz of 3GB.
TIA!
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тАО06-04-2010 01:33 AM
тАО06-04-2010 01:33 AM
Re: ksh limits - Max # of Env Variables and Contents
it would be around
(4096*10000)/1024/1024 ~40MB
and I suppose the current default maxdsiz value
1GB should be OK you have 3GB I guess.
Apps crew said new environment is twise as big as previous, I suppose it mean database is big or it can support more user or whatever apps for.
Did apps owner see any error while they faced the issue.
BR,
Kapil+
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тАО06-04-2010 01:49 AM
тАО06-04-2010 01:49 AM
Re: ksh limits - Max # of Env Variables and Contents
Is there a limit to the value of a korn shell variable?
Coz one of their issues is they're claiming there scripts are doing:
Envar="$Envar newstr"
(in some loop).
Thanks.
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тАО06-04-2010 01:50 AM
тАО06-04-2010 01:50 AM
Re: ksh limits - Max # of Env Variables and Contents
>>One-dimensional arrays are supported by the Korn shell. Arrays can have a maximum of
4096 elements
How can the variable more than 4096.
I am not sure if ksh93 also support more than that.
BR,
Kapil+
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тАО06-04-2010 06:59 AM
тАО06-04-2010 06:59 AM
Re: ksh limits - Max # of Env Variables and Contents
Time to use files or a database.
Or even shared memory?
At process creation the environ(5) is put on the stack.
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тАО06-05-2010 04:59 AM
тАО06-05-2010 04:59 AM
Re: ksh limits - Max # of Env Variables and Contents
Dennis gave you a better option. DO
not use such large Shell-based arrays. Very inefficient, not portable and prone
to hit limits in various Shells.
Some Shells offer larger array supports and
some do not even have such features.
For example, HP's POSIX-compliant Shell does
not offer such feature.
Here are the ones I know or heard of:
Bash: unlimited
Solaris /usr/xpg4/bin/sh: 4096
Ksh88: 1024
Ksh93: 4096
For example, HP-UX 11.23 Ksh is Ksh88.
Cheers,
VK2COT
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тАО06-05-2010 05:10 AM
тАО06-05-2010 05:10 AM
Re: ksh limits - Max # of Env Variables and Contents
One more surprise. I just tested it
on my Fedora 11 server at home.
According to the manual page, Ksh on this server supports maximum of 4194304 elements
in indexed (one-dimensional) array.
Looked too big, but test showed it was
actually correct:
Test script on Fedora 11:
#!/bin/ksh -x
set -A MyArr
MyArr[1023]="hola"
MyArr[4194303]="should-work-on Fedora-11"
MyArr[4194304]="should-fail-on Fedora-11"
Let's run it:
# myscript
+ set -A MyArr
+ MyArr[1023]=hola
+ MyArr[4194303]='should-work-on Fedora-11'
myscript: line 6: MyArr: subscript out of range
So, different Shells on different operating systems really have very different
maximum number of indices for arrays.
Cheers,
VK2COT
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тАО06-05-2010 07:37 AM
тАО06-05-2010 07:37 AM
Re: ksh limits - Max # of Env Variables and Contents
Arrays are very useful but as you have seen, there are too many variations on limits. I will use them for a few dozen items but would always switch to a file for larger values.
I do use variables to store large amounts of text (ie, VG=$(vgdisplay -v) which can then be reused as a memory-based resource with no further overhead. I have assigned 200 MBytes of text to a variable in the POSIX and ksh shell. Unfortunately, there does not appear to be any readable limits for each of the shells so you have to test big variables to see if it was successful. And of course, each variable's space is cumulative in the shell's work area, so you won't necessarily get 10 variables at 200 MB each.
> bumping of kernel param to the 32bit maxdsiz value of 4GB.
Won't do anything for any of the shells. They are compiled without the option to map additional quadrants. To expand heap memory will require changing the executable.
If the team really wants to use a shell with massive values (and does not care about portability), I would get Bash source code and compile it as a 64bit executable. Then 10 or 20 Gbytes can easily be allocated to the shell. But is it the appropriate tool? After all, shells (including Perl and even Java) are interpreters with a lot of overhead to run the scripts.
Bill Hassell, sysadmin
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тАО06-05-2010 09:32 AM
тАО06-05-2010 09:32 AM
Re: ksh limits - Max # of Env Variables and Contents
> Bill: After all, shells (including Perl and even Java) are interpreters with a lot of overhead to run the scripts.
As for Perl, it is actually both a compiler and an interpreter. Perl has no built-in size limits and allocates and deallocates memory automatically. It lies closer to C (upon which it is built) than any shell.
Regards!
...JRF...
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тАО06-05-2010 01:59 PM
тАО06-05-2010 01:59 PM
Re: ksh limits - Max # of Env Variables and Contents
Make sure you don't export these huge variables.