[Crash-utility] How to use scripts in crash?

[Dave Anderson]

----- Original Message -----
> 
> 
> > -----Original Message-----
> > From: crash-utility-bounces at redhat.com [mailto:crash-utility-
> > bounces at redhat.com] On Behalf Of Lei Wen
> > Sent: Wednesday, March 07, 2012 10:58 AM
> > To: Discussion list for crash utility usage, maintenance and development
> > Subject: [Crash-utility] How to use scripts in crash?
> > 
> > Hi Dave,
> > 
> > Do you have some guide doc that describe how to use the scripts in crash?
> > Like the example, I want to print out current filesystems registered.
> > I then need do following
> > 1. using "p" to get "file_systems" symbol value 2. using "list" with command as
> > "list -o file_system_type.next -s file_system_type.name,fs_flags <the file_systems  symbol value>"
> > 
> > So if the previous file_systems symbol value could be stored, and then I don't
> > need to copy the "p" result to "list" command by hand, but could let script do
> > such kind of thing.
> > 
> > I also notice there is "sial" script support in crash, but that is too complex for
> > me... I don't know how to start a basic usage with that... Is there any detailed
> > doc that could help me from a start?
> > 
> > Thanks,
> > Lei
> > 
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
> > https://www.redhat.com/mailman/listinfo/crash-utility
> 
> 
> Sial is a C interpreter with a few twists like the string type and its 
> associated operators.

> The ps example  is a good one. Using args and callbacks, including
> printing recursively (parent->siblings)  the process tree.
> Let me know if you have questions. I tried to comment the example as
> much as I could at the time. And yes, check out the readme files.
> 
> It also has a built in preprocessor which enables you to write/modify
> debugging code that easily adapts to the linux version of the core you
> are looking at.
> 
> All of the type and symbol information from kernel space is available in
> sial through the dwarf interface.
> You can combine these 2 features with the built in 'exists' operators on
> member and variables to enable yet better portability across various linux flavors.
> 
> SGI and other engineering outfits have been cut&pasting kernel code into
> sial scripts for years.
> 
> The hello worl skeleton for a sial command :
> ==
> string foo_opt(){ return "lt:h"; }
> string foo_usage() { return "[-l] [-t counter] [-h]\n"; }
> string foo_help(){return "  This is the help for command foo\n"}
> int
> foo()
> {
>     if(tflag) tval=atoi(targ)
>     if(lflag) {
>         printf("lflag is set, targ=[%s], targ);
>     }
>     printf("Hello world!\n");
> }
> ==
> By load'ing this file into crash you automatically create a callable
> foo command in crash, complete with help and usage.
> 
> Sial can be extended with 'sial builtins' and associated APis.
> If there are native crash functions (like back traces and fast searches)
> that can be useful as a function in sial, we can do that.
> 
>   -Luc

Thanks Luc -- that's exactly what we-the-uninitiated could use to
gain some traction in using sial, a solid but simple example script,
perhaps less sophisticated than the ps.c example.

The one above is a great start, although it's missing a couple of ";"
line endings and the first printf is missing the enclosing parenthesis.
And it seems to be missing some declarations for targ and tval?

  crash> help foo

  NAME
    foo - 

  SYNOPSIS
    foo [-l] [-t counter] [-h]


  DESCRIPTION
    This is the help for command foo


  crash> foo -l
  File script, line 9, Error: Unknown variable [targ]
  crash> foo -t 100
  File script, line 7, Error: Unknown variable [tval]
  crash> foo -h
  Hello world!
  crash> foo
  Hello world!
  crash>   

In any case, a very simple example that shows the basics such as
the above, as well as kernel-data access, and any other fundamentals
to get someone on their way would be *really* helpful to put on
the extensions page.  I've asked folks to forward me their sial
scripts on a number of occasions, but for whatever reason, nobody
has.

Thanks,
  Dave