Can ruby's puts or print draw horizontal line kind of like bash does with printf+tr does ?
printf '%20s\n' | tr ' ' -
this will draw:
--------------------
You can use the following snippet
puts "-"*20
Check this for more help.
You might be interested in formatting using ljust, rjust and center as well.
I use a quick puts "*"*80 for debug purposes. I'm sure there are better ways.
For fancy lines:
p 'MY_LINE'.center(80,'_-')
#=> "_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-MY_LINE_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_"
You could also have the following:
puts "".center(20, "-")
irb(main):005:0> puts "".center(20, '-')
=> "--------------------"
This could be more flexible if you wanted to add additional information:
irb(main):007:0> puts "end of task".center(20, "-")
----end of task-----
=> nil
You can also use String#ljust or String#rjust.
puts ''.rjust(20,"-")
# >> --------------------
puts ''.ljust(20,"-")
# >> --------------------
Related
I have a string that might have some of \n before the actual text. I want to add t-> after the new line character or characters. That means that once there is something else than '\n' in the string I want to insert 't->'.
Is there any simple way than
what = "\nrufus: ready" #result is "\nt->rufus: ready"
#what = "\n\nrufus: ready" #result is "\n\nt->rufus: ready"
#what = "\n\nrufus\n: ready" #result is "\n\nt->rufus: ready\n"
what.length.times do |i|
if (what[i,1] != "\n")
what.insert(i,"t->")
break
end
end
If I understand right, you want the following;
"abc def" => "t->abc def"
"\n\nabc def" => "\n\nt->abc def"
As such, I'd try;
string.sub(/^\n*/) do |newlines|
"#{newlines}t->"
end
If you want to insert some text at the end of every line:
original = "Hello\nWorld\nYay"
changed = original.gsub /$/, ' More!'
puts changed
#=> Hello More!
#=> World More!
#=> Yay More!
It's not a good idea to change the string as you iterate over it.
Presumably this is what you're looking for?
"\n\n".gsub("\n", "t->\n") # => "t->\nt->\n"
(substitute every instance of "\n" with "t->\n")
What could be the best way of getting the matching lines with the line numbers using Ruby's Enumerable#grep method. (as we use -n or --line-number switch with grep command).
Enumerable#grep doesn't let you do that, at least by default. Instead, I came up with:
text = 'now is the time
for all good men
to come to the aid
of their country'
regex = /aid/
hits = text.lines.with_index(1).inject([]) { |m,i| m << i if (i[0][regex]); m }
hits # => [["to come to the aid\n", 3]]
maybe something like this:
module Enumerable
def lgrep(pattern)
map.with_index.select{|e,| e =~ pattern}
end
end
This isn't elegant or efficient, but why not just number the lines before grepping?
You can kludge it in Ruby 1.8.6 like so:
require 'enumerator'
class Array
def grep_with_index(regex)
self.enum_for(:each_with_index).select {|x,i| x =~ regex}
end
end
arr = ['Foo', 'Bar', 'Gah']
arr.grep_with_index(/o/) # => [[0, 'Foo']]
arr.grep_with_index(/a/) # => [[1, 'Bar'], [2, 'Gah']]
Or if you're looking for tips on writing a grep-like utility in Ruby. Something like this should work:
def greplines(filename, regex)
lineno = 0
File.open(filename) do |file|
file.each_line do |line|
puts "#{lineno += 1}: #{line}" if line =~ regex
end
end
end
>> lines=["one", "two", "tests"]
=> ["one", "two", "tests"]
>> lines.grep(/test/){|x| puts "#{lines.index(x)+1}, #{x}" }
3, tests
To mash up the Tin Man's and ghostdog74's answers
text = 'now is the time
for all good men
to come to the aid
of their country'
regex = /aid/
text.lines.grep(/aid/){|x| puts "#{text.lines.find_index(x)+1}, #{x}" }
# => 3, to come to the aid
A modification to the solution given by the Tin Man. This snippet will return a hash having line numbers as keys, and matching lines as values. This one also works in ruby 1.8.7.
text = 'now is the time
for all good men
to come to the aid
of their country'
regex = /aid/
hits = text.lines.each_with_index.inject({}) { |m, i| m.merge!({(i[1]+1) => i[0].chomp}) if (i[0][regex]); m}
hits #=> {3=>"to come to the aid"}
Put text in a file
test.log
now is the time
for all good men
to come to the aid
of their country
Command line (alternative of grep or awk command )
ruby -ne ' puts $_ if $_=~/to the/' test.log
Try this also
ruby -na -e ' puts $F[2] if $_=~/the/' test.log
Similarly
ruby -na -e ' puts $_.split[2] if $_=~/the/' test.log
This is similar to awk command.
Another suggestion:
lines.find_index{ |l| l=~ regex }.
How can I get the first character in a string using Ruby?
Ultimately what I'm doing is taking someone's last name and just creating an initial out of it.
So if the string was "Smith" I just want "S".
You can use Ruby's open classes to make your code much more readable. For instance, this:
class String
def initial
self[0,1]
end
end
will allow you to use the initial method on any string. So if you have the following variables:
last_name = "Smith"
first_name = "John"
Then you can get the initials very cleanly and readably:
puts first_name.initial # prints J
puts last_name.initial # prints S
The other method mentioned here doesn't work on Ruby 1.8 (not that you should be using 1.8 anymore anyway!--but when this answer was posted it was still quite common):
puts 'Smith'[0] # prints 83
Of course, if you're not doing it on a regular basis, then defining the method might be overkill, and you could just do it directly:
puts last_name[0,1]
If you use a recent version of Ruby (1.9.0 or later), the following should work:
'Smith'[0] # => 'S'
If you use either 1.9.0+ or 1.8.7, the following should work:
'Smith'.chars.first # => 'S'
If you use a version older than 1.8.7, this should work:
'Smith'.split(//).first # => 'S'
Note that 'Smith'[0,1] does not work on 1.8, it will not give you the first character, it will only give you the first byte.
"Smith"[0..0]
works in both ruby 1.8 and ruby 1.9.
For completeness sake, since Ruby 1.9 String#chr returns the first character of a string. Its still available in 2.0 and 2.1.
"Smith".chr #=> "S"
http://ruby-doc.org/core-1.9.3/String.html#method-i-chr
In MRI 1.8.7 or greater:
'foobarbaz'.each_char.first
Try this:
>> a = "Smith"
>> a[0]
=> "S"
OR
>> "Smith".chr
#=> "S"
In Rails
name = 'Smith'
name.first
>> s = 'Smith'
=> "Smith"
>> s[0]
=> "S"
Another option that hasn't been mentioned yet:
> "Smith".slice(0)
#=> "S"
Because of an annoying design choice in Ruby before 1.9 — some_string[0] returns the character code of the first character — the most portable way to write this is some_string[0,1], which tells it to get a substring at index 0 that's 1 character long.
Try this:
def word(string, num)
string = 'Smith'
string[0..(num-1)]
end
If you're using Rails You can also use truncate
> 'Smith'.truncate(1, omission: '')
#=> "S"
or for additional formatting:
> 'Smith'.truncate(4)
#=> "S..."
> 'Smith'.truncate(2, omission: '.')
#=> "S."
While this is definitely overkill for the original question, for a pure ruby solution, here is how truncate is implemented in rails
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 66
def truncate(truncate_at, options = {})
return dup unless length > truncate_at
omission = options[:omission] || "..."
length_with_room_for_omission = truncate_at - omission.length
stop = if options[:separator]
rindex(options[:separator], length_with_room_for_omission) || length_with_room_for_omission
else
length_with_room_for_omission
end
"#{self[0, stop]}#{omission}"
end
Other way around would be using the chars for a string:
def abbrev_name
first_name.chars.first.capitalize + '.' + ' ' + last_name
end
Any of these methods will work:
name = 'Smith'
puts name.[0..0] # => S
puts name.[0] # => S
puts name.[0,1] # => S
puts name.[0].chr # => S
So I know in ruby that x.nil? will test if x is null.
What is the simplest way to test if x equals ' ', or ' '(two spaces), or ' '(three spaces), etc?
Basically, I'm wondering what the best way to test if a variable is all whitespace?
If you are using Rails, you can simply use:
x.blank?
This is safe to call when x is nil, and returns true if x is nil or all whitespace.
If you aren't using Rails you can get it from the activesupport gem. Install with gem install activesupport. In your file either require 'active_support/core_ext to get all active support extensions to the base classes, or require 'active_support/core_ext/string' to get just the extensions to the String class. Either way, the blank? method will be available after the require.
"best" depends on the context, but here is a simple way.
some_string.strip.empty?
s =~ /\A\s*\Z/
Regex solution. Here's a short ruby regex tutorial.
If x is all whitespace, then x.strip will be the empty string. So you can do:
if not x.nil? and x.strip.empty? then
puts "It's all whitespace!"
end
Alternatively, using a regular expression, x =~ /\S/ will return false if and only if x is all whitespace characters:
if not (x.nil? or x =~ /\S/) then
puts "It's all whitespace!"
end
a = " "
a.each_byte do |x|
if x == 32
puts "space"
end
end
Based on your comment I think you can extend the String class and define a spaces? method as follows:
$ irb
>> s = " "
=> " "
>> s.spaces?
NoMethodError: undefined method `spaces?' for " ":String
from (irb):2
>> class String
>> def spaces?
>> x = self =~ /^\s+$/
>> x == 0
>> end
>> end
=> nil
>> s.spaces?
=> true
>> s = ""
=> ""
>> s.spaces?
=> false
>>
s.include?(" ")
Examples:
s = "A B C D"
s.include?(" ") #=> true
s = "ABCD"
s.include?(" ") #=> false
Yet another :) string.all? { |c| c == ' ' }
I thought this code would work, but the regular expression doesn't ever match the \r\n. I have viewed the data I am reading in a hex editor and verified there really is a hex D and hex A pattern in the file.
I have also tried the regular expressions /\xD\xA/m and /\x0D\x0A/m but they also didn't match.
This is my code right now:
lines2 = lines.gsub( /\r\n/m, "\n" )
if ( lines == lines2 )
print "still the same\n"
else
print "made the change\n"
end
In addition to alternatives, it would be nice to know what I'm doing wrong (to facilitate some learning on my part). :)
Use String#strip
Returns a copy of str with leading and trailing whitespace removed.
e.g
" hello ".strip #=> "hello"
"\tgoodbye\r\n".strip #=> "goodbye"
Using gsub
string = string.gsub(/\r/," ")
string = string.gsub(/\n/," ")
Generally when I deal with stripping \r or \n, I'll look for both by doing something like
lines.gsub(/\r\n?/, "\n");
I've found that depending on how the data was saved (the OS used, editor used, Jupiter's relation to Io at the time) there may or may not be the newline after the carriage return. It does seem weird that you see both characters in hex mode. Hope this helps.
If you are using Rails, there is a squish method
"\tgoodbye\r\n".squish => "goodbye"
"\tgood \t\r\nbye\r\n".squish => "good bye"
What do you get when you do puts lines? That will give you a clue.
By default File.open opens the file in text mode, so your \r\n characters will be automatically converted to \n. Maybe that's the reason lines are always equal to lines2. To prevent Ruby from parsing the line ends use the rb mode:
C:\> copy con lala.txt
a
file
with
many
lines
^Z
C:\> irb
irb(main):001:0> text = File.open('lala.txt').read
=> "a\nfile\nwith\nmany\nlines\n"
irb(main):002:0> bin = File.open('lala.txt', 'rb').read
=> "a\r\nfile\r\nwith\r\nmany\r\nlines\r\n"
irb(main):003:0>
But from your question and code I see you simply need to open the file with the default modifier. You don't need any conversion and may use the shorter File.read.
modified_string = string.gsub(/\s+/, ' ').strip
lines2 = lines.split.join("\n")
"still the same\n".chomp
or
"still the same\n".chomp!
http://www.ruby-doc.org/core-1.9.3/String.html#method-i-chomp
How about the following?
irb(main):003:0> my_string = "Some text with a carriage return \r"
=> "Some text with a carriage return \r"
irb(main):004:0> my_string.gsub(/\r/,"")
=> "Some text with a carriage return "
irb(main):005:0>
Or...
irb(main):007:0> my_string = "Some text with a carriage return \r\n"
=> "Some text with a carriage return \r\n"
irb(main):008:0> my_string.gsub(/\r\n/,"\n")
=> "Some text with a carriage return \n"
irb(main):009:0>
I think your regex is almost complete - here's what I would do:
lines2 = lines.gsub(/[\r\n]+/m, "\n")
In the above, I've put \r and \n into a class (that way it doesn't matter in which order they might appear) and added the "+" qualifier (so that "\r\n\r\n\r\n" would also match once, and the whole thing replaced with "\n")
Just another variant:
lines.delete(" \n")
Why not read the file in text mode, rather than binary mode?
lines.map(&:strip).join(" ")
You can use this :
my_string.strip.gsub(/\s+/, ' ')
def dos2unix(input)
input.each_byte.map { |c| c.chr unless c == 13 }.join
end
remove_all_the_carriage_returns = dos2unix(some_blob)