Eric Schrock wrote:
> You have a couple different things in play here.
>
> First, MDB pipelines only work with uintptr_t's, not arbitrary text. So
> when you try to pipe something like "foo: X" or "X Y Z" to another dcmd,
> the parser will choke.
>
> Normally, the formatting commands ('/' and friends) recognize when you
> are in pipe context and omit any extraneous formatting characters.
> Since they only output numbers, they are safe to use in pipe context.
>
> However, under ::eval, any notion of pipe context is (intentionally)
> ignored. So ::eval '/Kn' will print the extra formatting characters
> (such as "swap_vnodes:") as it has no way of knowing it's being used in
> pipe context outside the eval context. One way to get around this is to
> do something like:
>
> ::array ... p | ::eval '<p/Kn | =Kn' | ::grep .==0
>
Hi Eric,
I really appreciate your kindness to explain this for me.
::array ... p | ::eval '<p/Kn | =Kn' gives pure uintptr_t's so it works well
with mdb pipeline. What I am suprized is that ::array ... p | /Kn *doesn't*
give pure uintptr_t's, as its output has an address in the first line, so I
expect it will break the mdb pipeline, but instead it works. Am I missing
anything here?
Many thanks,
Zhijun
------------------------------------------------
[The output of /Kn and ::eval '<p/Kn | =Kn']
> fffffffecb5bc000::array "struct vnode *" 10 p |/Kn
*0xfffffffecb5bc000: 0 // I think this will break the
pipeline, but it doesn't *
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> fffffffecb5bc000::array "struct vnode *" 10 p | ::eval '<p/Kn | =Kn'
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> That being said, for this particular case you do not need the '::eval
> <p' at all, since it's identical to the output from '::array'.
>
> - Eric
>
> On Fri, Aug 24, 2007 at 11:29:01PM +0800, zhijun wrote:
>
>> While I still have some doublt for my second question, in which,
>> fffffffecc47e000::array "struct vnode *" 0t2048 p|::eval <p/K|::grep
>> .==0 doesn't work.
>>
>> > swap_vnodes/K
>> swap_vnodes:
>> swap_vnodes: fffffffecb5bc000
>>
>> > fffffffecb5bc000::array "struct vnode *" 10
>> fffffffecb5bc000
>> fffffffecb5bc008
>> fffffffecb5bc010
>> fffffffecb5bc018
>> fffffffecb5bc020
>> fffffffecb5bc028
>> fffffffecb5bc030
>> fffffffecb5bc038
>> fffffffecb5bc040
>> fffffffecb5bc048
>> fffffffecb5bc050
>> fffffffecb5bc058
>> fffffffecb5bc060
>> fffffffecb5bc068
>> fffffffecb5bc070
>> fffffffecb5bc078
>>
>> Use ::grep pipelined with ::eval<p=K can work while with ::eval <p/K
>> doesn't work
>>
>> > fffffffecb5bc000::array "struct vnode *" 10 p|::eval <p=K|::grep
>> .==0 /* this works */
>> > fffffffecb5bc000::array "struct vnode *" 10 p|::eval <p/K|::grep
>> .==0 /* this doesn't work */
>> mdb: syntax error on line 1 of (pipeline) near ":"
>>
>> > fffffffecb5bc000::array "struct vnode *" 10 p|::eval <p=K
>> fffffffecb5bc000
>> fffffffecb5bc008
>> fffffffecb5bc010
>> fffffffecb5bc018
>> fffffffecb5bc020
>> fffffffecb5bc028
>> fffffffecb5bc030
>> fffffffecb5bc038
>> fffffffecb5bc040
>> fffffffecb5bc048
>> fffffffecb5bc050
>> fffffffecb5bc058
>> fffffffecb5bc060
>> fffffffecb5bc068
>> fffffffecb5bc070
>> fffffffecb5bc078
>> > fffffffecb5bc000::array "struct vnode *" 10 p|::eval <p/K
>> 0xfffffffecb5bc000: 0
>> 0xfffffffecb5bc008: 0
>> 0xfffffffecb5bc010: 0
>> 0xfffffffecb5bc018: 0
>> 0xfffffffecb5bc020: 0
>> 0xfffffffecb5bc028: 0
>> 0xfffffffecb5bc030: 0
>> 0xfffffffecb5bc038: 0
>> 0xfffffffecb5bc040: 0
>> 0xfffffffecb5bc048: 0
>> 0xfffffffecb5bc050: 0
>> 0xfffffffecb5bc058: 0
>> 0xfffffffecb5bc060: 0
>> 0xfffffffecb5bc068: 0
>> 0xfffffffecb5bc070: 0
>> 0xfffffffecb5bc078: 0
>>
>> Looking at the above output, I guess the reason is the output format, I
>> checked "Solaris Modular Debugger Guide" and on page 32 it says each
>> line in the output before '|' must consist of an arithmetic expression
>> terminated by a NEWLINE or semicolon. So it seems that the reason here
>> is that the output of ::eval <p=K doesn't conform to this thus breaks
>> the pipeline of dcmds. But let's look at the output of /Kn
>>
>> > fffffffecb5bc000::array "struct vnode *" 10 |/Kn
>> 0xfffffffecb5bc000: 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> > fffffffecb5bc000::array "struct vnode *" 10 |/Kn|::grep .==0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>> 0
>>
>> My two questions here:
>> While /n is added to make sure each expression occupies one line, here
>> the first line does not exactly consist of an arithmetic expression, and
>> it contains the address of the first entry in array, so I would expect
>> it will break the pineline, but instead, it works fine. I am somehow
>> puzzled about this. Could you give me some hint on this?
>> Another question is why the output of /Kn and ::eval <p/K are different?
>> Basically I think the output should be the same as they each takes an
>> address and dump the content one line a time.
>>
>> Thanks again,
>> Zhijun
>>
>>
>>
>>
>> _______________________________________________
>> mdb-discuss mailing list
>> mdb-discuss at opensolaris.org
>>
>
> --
> Eric Schrock, Solaris Kernel Development http://blogs.sun.com/eschrock
>
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