How to read the first line from a file?

[Aleksey Tsalolikhin]

Is there a simpler way to do this in native CFEngine code?

{{{

vars:

   "os"

       slist => splitstring(readfile("/etc/issue", 99), "\n", 1);

}}}

I was kind of thinking readline("/path/to/file", 1) but there is no readline() function

--

Aleksey Tsalolikhin

CFEngine Training & Consulting

Vertical Sysadmin, Inc.

+1-323-393-0779

[Neil Watson]

On Wed, Sep 02, 2015 at 06:10:46PM -0700, Aleksey Tsalolikhin wrote:
> Is there a simpler way to do this in native CFEngine code?
> {{{
> vars:
>    "os"
>        slist => splitstring(readfile("/etc/issue", 99), "\n", 1);
> }}}
> I was kind of thinking readline("/path/to/file", 1) but there is no
> readline() function

readstringlist?

https://docs.cfengine.com/latest/reference-functions-readintrealstringlist.html

--
Neil H Watson
Sr. Partner, Architecture and Infrastructure
CFEngine reporting: https://github.com/evolvethinking/delta_reporting
CFEngine policy: https://github.com/evolvethinking/evolve_cfengine_freelib
CFEngine and vim: https://github.com/neilhwatson/vim_cf3
CFEngine support: http://evolvethinking.com

[Aleksey Tsalolikhin]

On Wed, Sep 2, 2015 at 6:19 PM, Neil Watson <cfen...@watson-wilson.ca> wrote:

On Wed, Sep 02, 2015 at 06:10:46PM -0700, Aleksey Tsalolikhin wrote:

  Is there a simpler way to do this in native CFEngine code?
  {{{
  vars:
     "os"
         slist => splitstring(readfile("/etc/issue", 99), "\n", 1);
  }}}
  I was kind of thinking readline("/path/to/file", 1) but there is no
  readline() function

readstringlist?

https://docs.cfengine.com/latest/reference-functions-readintrealstringlist.html

Yeah, I thought so too but I couldn't understand how to use it.  :(

The example is incomplete, it shows the RHS but not the LHS:

Example:

    readintarray("array_name","/tmp/array","#[^\n]*",":",10,4000);

Aside: If I didn't have to sleep, I would go through the documentation and make the examples (more) comprehensible by making them runnable.

I tried to work it out, and this is what I got:

{{{

# cat test.cf

bundle agent example 

{

vars:

   "some_integer"

       int => readintarray("array_name","/tmp/array","#[^\n]*",":",10,4000);

   "indices"

       slist => getindices("array_name");

reports:

  "Indices = $(indices)";

  "Array contents = $(array_name[$(indices)])";

}

# cf-agent -f ./test.cf -b example -K

R: Indices = 4

R: Indices = 3

R: Indices = 1

R: Indices = 2

R: Array contents = $(array_name[4])

R: Array contents = $(array_name[3])

R: Array contents = $(array_name[1])

R: Array contents = $(array_name[2])

#

}}}

I feel like I'm halfway there...

[Nick Anderson]

On 09/03/2015 01:37 PM, Aleksey Tsalolikhin wrote:
> "Array contents = $(array_name[$(indices)])";

Can you provide the sample input data?

Without trying myself, perhaps $(array_name[$(indices)][0]) or
$(array_name[$(indices)][1])

[Aleksey Tsalolikhin]

Thanks, Nick, I think that did it:

# cat /tmp/array 

1: 5:7:21:13

2:19:8:14:14

3:45:1:78:22

4:64:2:98:99

# cat test.cf 

bundle agent example 

{

vars:

   "some_integer"

       int => readintarray("array_name","/tmp/array","#[^\n]*",":",10,4000);

   "indices"

       slist => getindices("array_name");

reports:

  "Indices = $(indices)";

  "First element = $(array_name[$(indices)][0])";

  "Second element = $(array_name[$(indices)][1])";

  "Third element = $(array_name[$(indices)][2])";

}

# cf-agent -f ./test.cf -b example -K

R: Indices = 4

R: Indices = 3

R: Indices = 1

R: Indices = 2

R: First element = 4

R: First element = 3

R: First element = 1

R: First element = 2

R: Second element = 64

R: Second element = 45

R: Second element = 5

R: Second element = 19

R: Third element = 2

R: Third element = 1

R: Third element = 7

R: Third element = 8

# 

[Neil Watson]

I may not understand your desire, but:

body common control
{
bundlesequence => { "main", };
}

bundle agent main
{
vars:
"hosts_line_one" slist => readstringlist(
"/etc/hosts",
"^\s#",
"\n",
"1",
"10"
);

reports:
"line => ${hosts_line_one}";
}

Produces:
R: line => 127.0.0.1

[Aleksey Tsalolikhin]

Lovely, thanks, Neil!

Now I can harvest the OS id (e.g. 'CentOS release 6.6 (Final)') to add to inventory.

(I don't have "lsb_release" command so I have to harvest the OS name and version from /etc/issue.)

{{{

  vars:

     "etc_issue_line_one"

       slist => readstringlist(

                               "/etc/issue", 

                               "^\s#", # regex matching comments

                               "\n",   # regex to split lines into fields

                               "1",    # maxentries

                               "80"    # maximum bytes to read

                               ),

       comment => "Read the first line from the OS banner in

                   /etc/issue to get OS name and version";

     "os_banner"

       comment => "Convert slist to string so it looks pretty in Inventory UI",

       string => join("", "etc_issue_line_one"),

       meta => { "inventory", "attribute_name=OS Name and Version" };

}}}

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[Neil Watson]

On Thu, Sep 03, 2015 at 12:13:46PM -0700, Aleksey Tsalolikhin wrote:
> Lovely, thanks, Neil!
> Now I can harvest the OS id (e.g. 'CentOS release 6.6 (Final)') to add
> to inventory.
> (I don't have "lsb_release" command so I have to harvest the OS name and
> version from /etc/issue.)

Issue is often changed by sysadmins. It should not be relied on. Why are
trying to get this? Isn't it already a hard class: centos_6_6?

[Aleksey Tsalolikhin]

On Sep 3, 2015 12:19 PM, "Neil Watson" <cfen...@watson-wilson.ca> wrote:

Issue is often changed by sysadmins. It should not be relied on. Why are
trying to get this? Isn't it already a hard class: centos_6_6?

I did try using hard classes originally (a few months ago) but it didn't work on all the kinds servers I have to support.  I don't remember what the outlier was but I resorted to parsing /etc/issue, which, as you say, is liable to being modified by local staff.

I may revisit this.  I was under a lot of pressure at the time to get the thing working quickly. The advantage of using all hard classes would be the policy would run faster and we'd get rid of this potential liability.

[Brian Bennett]

Is $(sys.os) not correct?

-- 

Brian Bennett

Looking for CFEngine training?

http://www.verticalsysadmin.com/

--

[Aleksey Tsalolikhin]

On Fri, Sep 4, 2015 at 9:45 AM, Brian Bennett <brian....@verticalsysadmin.com> wrote:

Is $(sys.os) not correct?

sys.os

The name of the operating system according to the kernel.

# os = linux

 

Oh, it's correct, but all my operating systems are "linux", Brian.   :-)  I need to know the distribution name (e.g. RHEL or CentOS or Oracle Enterprise Linux, etc.) and the version of the distribution.

Do I smell the need for $(sys.os_name) and $(sys.os_version) ?   I bet that would be useful in inventory in many sites.

[Eystein Måløy Stenberg]

There is $(inventory_os.description) that uses LSB if available. Or you
can use $(sys.flavor).

On 04/09/15 11:06, Aleksey Tsalolikhin wrote:
> On Fri, Sep 4, 2015 at 9:45 AM, Brian Bennett
> <brian....@verticalsysadmin.com

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[Aleksey Tsalolikhin]

On Fri, Sep 4, 2015 at 11:09 AM, Eystein Måløy Stenberg <eystein.mal...@cfengine.com> wrote:

There is $(inventory_os.description) that uses LSB if available.

Thank you, but LSB is not available.  =)  

 

Or you can use $(sys.flavor).

sys.flavor, sys.flavour

A variable containing an operating system identification string that is used to determine the current release of the operating system in a form that can be used as a label in naming. This is used, for instance, to detect which package name to choose when updating software binaries for CFEngine.

 

$ cf-agent -f ./temp.cf -b example

R: redhat_6

$ cat /etc/redhat-release

Red Hat Enterprise Linux Server release 6.2 (Santiago)

$

# cf-agent -f ./temp.cf -b example

R: centos_6

# cat /etc/centos-release 

CentOS release 6.6 (Final)

# 

I need to inventory the release of the operating system (i.e. number of RHEL 6.2 versus number of RHEL 6.6).

I would expect a CFEngine system variable that would provide the release version of the operating system (such as 6.6). =)  

 

[Brian Bennett]

I would go for sys.distribution.

In the mean time, I'd recommend making a module that can emit extra variables. Something similar to what I do for Triton/SmartOS metadata (https://github.com/bahamat/cfengine-smartos-metadata).

-- 

Brian Bennett

Looking for CFEngine training?

http://www.verticalsysadmin.com/

[Brian Bennett]

In the past I used classes for that kind of thing. E.G., redhat_6_2 vs redhat_6_6.

-- 

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Looking for CFEngine training?

http://www.verticalsysadmin.com/

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[Aleksey Tsalolikhin]

On Fri, Sep 4, 2015 at 12:02 PM, Brian Bennett <brian....@verticalsysadmin.com> wrote:

In the past I used classes for that kind of thing. E.G., redhat_6_2 vs redhat_6_6.

Right.  Here's what I've concocted to inventory the OS distribution (name and major.minor version number):

      "os_name"

        slist => { "redhat", "centos", "oracle" };

      "major"

        slist  => { "4", "5", "6", "7" };

      "minor"

        slist  => { "1", "2", "3", "4" , "5", "6", "7", "8", "9", "10" };

      "detailed_flavor"

        string => "$(os_name) $(major).$(minor)",

        ifvarclass => "$(os_name)_$(major)_$(minor)",

        meta => { "inventory", "attribute_name=OS Flavor by Name and Major.Minor" };

In action:

R:      DEBUG inventory_redhat_version: Added to inventory: 'OS Flavor by Name and Major.Minor' = 'redhat 6.2'

Thanks for the help, all!

Best,

-at