Stderr stdout redirection with Ruby?

ruby-talk
1

i do have a shell script doing :

`man "#{arg}" 2> "#{tmp}/#{fm}" PIPE man2html > "#{tmp}/#{f1}"`

because i want to know if there is "No manual entry for "#{arg}""

then for the time being i'm using an tmp file "#{tmp}/#{fm}" which i
read after to know i i get the message :

"No manual entry for "#{arg}""

i'm sure there is a more elegant way doing that in Ruby, avoiding
shelling, BUT HOW TO ?

2

i do have a shell script doing :

`man "#{arg}" 2> "#{tmp}/#{fm}" PIPE man2html > "#{tmp}/#{f1}"`

because i want to know if there is "No manual entry for "#{arg}""

then for the time being i'm using an tmp file "#{tmp}/#{fm}" which i
read after to know i i get the message :

"No manual entry for "#{arg}""

i'm sure there is a more elegant way doing that in Ruby, avoiding
shelling, BUT HOW TO ?

If you want to do it completely within Ruby, you could first slurp the
output of man into a Ruby variable, i.e.

  man_page=%x(man #{arg})
  
and if it is OK, i.e.

  if man_page.length > 0
     ...
send this as stdin into man2html, i.e. something like:

  to_html=IO.popen("man2html >#{f1}","w")
  to_html.print(man_page)
  to_html.close

From a logical point of view, this solution has the advantage
that you don't overwrite your file f1 if the man page does not exist.

For a simpler solution (a bit dirty, but less keystrokes), you might
consider
the following idea, which however *does* use a shell:

  error_message=%x[(man #{arg}|man2html >#{f1}) 2>&1]

After this, error_message contains whatever man and/org man2html spilled
out onto stderr, but f1 is always overwritten (even if there is no man
page).

HTH,

Ronald

···

--
Ronald Fischer <ronald.fischer@venyon.com>
Phone: +49-89-452133-162

3

require 'rubygems'
require 'open4'

stdin = '', stdout = '', stderr = ''

Open4.spawn cmd, :stdin=>stdin, :stdout=>stdout, :stderr=>stderr

there are many example in the dist and postings on this list.

a @ http://drawohara.com/

···

On Aug 10, 2007, at 3:30 AM, unbewust wrote:

i'm sure there is a more elegant way doing that in Ruby, avoiding
shelling, BUT HOW TO ?

--
we can deny everything, except that we have the possibility of being better. simply reflect on that.
h.h. the 14th dalai lama

4

OK, fine thanks, in fact f1 is never overwritten the way i use it ...

thanks a lot !

···

On 10 août, 13:26, "Ronald Fischer" <ronald.fisc...@venyon.com> wrote:

> i do have a shell script doing :

> `man "#{arg}" 2> "#{tmp}/#{fm}" PIPE man2html > "#{tmp}/#{f1}"`

> because i want to know if there is "No manual entry for "#{arg}""

> then for the time being i'm using an tmp file "#{tmp}/#{fm}" which i
> read after to know i i get the message :

> "No manual entry for "#{arg}""

> i'm sure there is a more elegant way doing that in Ruby, avoiding
> shelling, BUT HOW TO ?

If you want to do it completely within Ruby, you could first slurp the
output of man into a Ruby variable, i.e.

  man_page=%x(man #{arg})

and if it is OK, i.e.

  if man_page.length > 0
     ...
send this as stdin into man2html, i.e. something like:

  to_html=IO.popen("man2html >#{f1}","w")
  to_html.print(man_page)
  to_html.close

From a logical point of view, this solution has the advantage
that you don't overwrite your file f1 if the man page does not exist.

For a simpler solution (a bit dirty, but less keystrokes), you might
consider
the following idea, which however *does* use a shell:

  error_message=%x[(man #{arg}|man2html >#{f1}) 2>&1]

After this, error_message contains whatever man and/org man2html spilled
out onto stderr, but f1 is always overwritten (even if there is no man
page).

5

By using 'man_page=%x(man #{arg})' you're shelling out as well. It's the
same as writing 'man_page = `man #{arg}`'. However, it's probably good to
do the checking / conversion stuff inside ruby and shell out multiple times
rather than having actual program flow / code in sh scripting :D.

···

On Friday 10 August 2007 04:26:00 am Ronald Fischer wrote:

> i do have a shell script doing :
>
> `man "#{arg}" 2> "#{tmp}/#{fm}" PIPE man2html > "#{tmp}/#{f1}"`
>
> because i want to know if there is "No manual entry for "#{arg}""
>
> then for the time being i'm using an tmp file "#{tmp}/#{fm}" which i
> read after to know i i get the message :
>
> "No manual entry for "#{arg}""
>
> i'm sure there is a more elegant way doing that in Ruby, avoiding
> shelling, BUT HOW TO ?

If you want to do it completely within Ruby, you could first slurp the
output of man into a Ruby variable, i.e.

  man_page=%x(man #{arg})
  
and if it is OK, i.e.

  if man_page.length > 0
     ...
send this as stdin into man2html, i.e. something like:

  to_html=IO.popen("man2html >#{f1}","w")
  to_html.print(man_page)
  to_html.close

From a logical point of view, this solution has the advantage
that you don't overwrite your file f1 if the man page does not exist.

For a simpler solution (a bit dirty, but less keystrokes), you might
consider
the following idea, which however *does* use a shell:

  error_message=%x[(man #{arg}|man2html >#{f1}) 2>&1]

After this, error_message contains whatever man and/org man2html spilled
out onto stderr, but f1 is always overwritten (even if there is no man
page).

HTH,

Ronald

--
Konrad Meyer <konrad@tylerc.org> http://konrad.sobertillnoon.com/

6

Fine ! thanks a lot !!!

···

On 10 août, 23:02, "ara.t.howard" <ara.t.how...@gmail.com> wrote:

On Aug 10, 2007, at 3:30 AM, unbewust wrote:

> i'm sure there is a more elegant way doing that in Ruby, avoiding
> shelling, BUT HOW TO ?

require 'rubygems'
require 'open4'

stdin = '', stdout = '', stderr = ''

Open4.spawn cmd, :stdin=>stdin, :stdout=>stdout, :stderr=>stderr

there are many example in the dist and postings on this list.

a @http://drawohara.com/

7

i've tested allready, unfortunately i get a " undefined method spawn
for main object" after having included it...

Yvon

···

On 10 août, 23:02, "ara.t.howard" <ara.t.how...@gmail.com> wrote:

On Aug 10, 2007, at 3:30 AM, unbewust wrote:

> i'm sure there is a more elegant way doing that in Ruby, avoiding
> shelling, BUT HOW TO ?

require 'rubygems'
require 'open4'

stdin = '', stdout = '', stderr = ''

Open4.spawn cmd, :stdin=>stdin, :stdout=>stdout, :stderr=>stderr

8

>
>
>
> > i'm sure there is a more elegant way doing that in Ruby, avoiding
> > shelling, BUT HOW TO ?
>
> require 'rubygems'
> require 'open4'
>
> stdin = '', stdout = '', stderr = ''
>
> Open4.spawn cmd, :stdin=>stdin, :stdout=>stdout, :stderr=>stderr

i've tested allready, unfortunately i get a " undefined method spawn
for main object" after having included it...

Did you do this?
include Open4

spawn cmd, ...

Because that's not going to work

spawn is a singleton method of the Open4 module.

Yvon

···

On 8/11/07, unbewust <yvon.thoraval@gmail.com> wrote:

On 10 août, 23:02, "ara.t.howard" <ara.t.how...@gmail.com> wrote:
> On Aug 10, 2007, at 3:30 AM, unbewust wrote: