Ruby script to read file line by line and do if statments with puts?

Question

I am trying to write a script that will fill out a mapping of equipment by using if statments on a text file.

Here is the code I have tried:

input.txt:

SWITCH
ROUTER
FIREWALL
ROUTER
ROUTER
FIREWALL
SWITCH
SWITCH

Ruby code:

IO.foreach("input.txt") do |type_equipment|
  if type_equipment = "SWITCH"
    puts "SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch"
  elsif type_equipment = "ROUTER"
    puts "ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router"
  elsif type_equipment = "FIREWALL"
    puts "FIREWALL,BMC_COMPUTERSYSTEM,Network,Appliance,Firewall"
  end
end

The code runs but it is outputting this:

SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
main.rb:6: warning: found = in conditional, should be ==
main.rb:4: warning: found = in conditional, should be ==
main.rb:2: warning: found = in conditional, should be ==

I want it to evaluate each line in the file and if it matches an if statement, then output the associated puts.

I have also tied the == for the if statements but it only displays the result for the first line only with no warnings.

score 3 · Accepted Answer · answered Aug 21 '14 at 18:03

Please indent your code properly
As the error message suggests, you must use == instead of = for comparison (= is variable assignment)
There is a newline at the end of type_equipment which you can remove with String#chomp
Conditionals have the last expression as return value, so you can write a single puts in front of the if instead of repeating it inside the blocks
I recommend using case instead of repetitive if statements

These suggestions would result in:

IO.foreach("input.txt") do |type_equipment|
  puts case type_equipment.chomp
    when "SWITCH"   then "SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch"
    when "ROUTER"   then "ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router"
    when "FIREWALL" then "FIREWALL,BMC_COMPUTERSYSTEM,Network,Appliance,Firewall"
  end
end

score 2 · Answer 2 · edited Aug 21 '14 at 19:10

2

main.rb:6: warning: found = in conditional, should be ==

The answer is right in front of you.

When comparing two things you use var1==var2.

var1=var2 is an assignment operator, it sets the value of var1 equal to the value of var2, so your code should be:

IO.foreach("input.txt") do |type_equipment|
if type_equipment == "SWITCH"
  puts "SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch"
 elsif type_equipment == "ROUTER"
  puts "ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router"
 elsif type_equipment == "FIREWALL"
   puts "FIREWALL,BMC_COMPUTERSYSTEM,Network,Appliance,Firewall"
  end
end

edited Aug 21 '14 at 19:10

the Tin Man

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answered Aug 21 '14 at 17:40

QuinnFTW

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No this only outputs 1 result: SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch – emvee Aug 21 '14 at 17:43
Im not sure, but I usually loop through a file in ruby like this: http://alvinalexander.com/blog/post/ruby/how-process-line-text-file-ruby – QuinnFTW Aug 21 '14 at 17:46
I think it doesn't work because there's a newline at the end of `type_equipment`. – Patrick Oscity Aug 21 '14 at 18:05
you can do type_equipment.delete("\n")==var then – QuinnFTW Aug 21 '14 at 18:31
"I think it doesn't work because there's a newline at the end of type_equipment". `foreach` strips trailing new-lines when the record is read from a file. – the Tin Man Aug 21 '14 at 19:11
Yes, you're correct. I was thinking of the result after splitting a line, which normally won't return the line-end. – the Tin Man Aug 22 '14 at 16:58
@theTinMan, I just deleted my comment. You might want to delete your last two, just to clean this up. I'll delete this comment later... – Cary Swoveland Aug 23 '14 at 20:07

Cary Swoveland · Answer 3 · 2014-08-21T20:49:42.960

To make it easier to maintain your code when new equipment is added or existing equipment retired, consider using a hash:

hash = {"SWITCH" => "SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch",
        "ROUTER" => "ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router",
        "FIREWALL" => "FIREWALL,BMC_COMPUTERSYSTEM,Network,Appliance,Firewall"}

equipment =
"SWITCH
ROUTER
FIREWALL
ROUTER
PINGER
ROUTER
FIREWALL
SWITCH
SWITCH"

equipment.each_line do |l|
  equip = l.strip
  puts hash[equip] if hash.key?(equip)
end
  # SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
  # ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router
  # ...
  # SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch

or, if you prefer:

equipment.each_line do |l|
  equip = l.strip
  puts (hash.key?(equip) ? hash[equip] : "***What the heck is a '#{equip}'??")
end
  # SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch
  # ...
  # ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router
  # ***What the heck is a 'PINGER'??
  # ROUTER,BMC_COMPUTERSYSTEM,Network,Router,Ethernet Router
  # ...
  # SWITCH,BMC_COMPUTERSYSTEM,Network,Switch,Ethernet Switch

You could use String#chomp rather than String#strip, but I chose the latter because it removes any spaces fore and aft as well as the newline character. When reading from a file, you will want to use the enumerator IO#foreach.

Ruby script to read file line by line and do if statments with puts?

3 Answers3