is it possible to do something like this?
File.open('/etc/logo', 'r') do |f|
f.each_line{ |line| puts line }
end
But I don't want the content of lines to be printed as text but rather figured out as arguments to the puts command. To make myself clear, this is the example /etc/logo:
"\e[34m" + 'BLUE COLOR' + "\e[31m" + 'RED COLOR'
I want to separate the ASCII logo from my code. Thank you for your ideas.
File.open('/etc/logo', 'r') do |f|
f.each_line{ |line| eval "puts #{line}" }
end
Don't let anyone edit that file.
If you want a more secure way to do it, try this:
File.open('/etc/logo', 'r') do |f|
f.each_line{ |line|
puts line.gsub(/\\e/, "\e")
}
end
For this, you should use a file like:
\e[34mBLUE COLOR\e[31mRED COLOR
This just replaces the escaped \e with the real character.
Related
I'm a newbie! I have a text file that contains lines and lines of text. I want to try to create a code that only allows the lines that have the phrase "larry.bird" show while the others are deleted. This is my current code...
File.open("HM.txt").each do |line|
puts line
if line.include? "larry.bird"
puts "larye.bird " + line
end
end
File.readlines('HM.txt') do |li|
puts li if (li['larry.bird'])
end
If you can help me out, that would be awesome!
You're pretty close. You're opening and reading the file correctly; you're just accidentally printing every line before performing the check. The puts line on the second line of your code is ensuring that this occurs.
File.open("HM.txt") do |file|
file.each_line do |line|
if line.include? "larry.bird"
puts "larry.bird " + line
end
end
end
We can also shorten one-line if statements in Ruby, using suffix notation that often makes code more concise.
File.open("HM.txt") do |file|
file.each_line do |line|
puts "larry.bird " + line if line.include? "larry.bird"
end
end
This is equivalent to the first example.
I know that I can replace text as below in a file
File.write(file, File.read(file).gsub(/text/, "text_to_replace"))
Can we also use sub/gsub to:-
Replace a string on a particular line number (useful when there is a same string at different locations in a file)
Example
root#vikas:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
correct minor mistakes
add related resources or links
root#box27:~#
I want to insert some text at 3rd line
root#vikas:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
Hello, how are you ?
correct minor mistakes
add related resources or links
root#box27:~
Replace a string on the line just before/after matching a pattern
Example
root#vikas:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
correct minor mistakes
add related resources or links
root#box27:~#
I want to search 'minor mistakes' and put text 'Hello, how are you ?' before that.
root#vikas:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
Hello, how are you ?
correct minor mistakes
add related resources or links
root#box27:~
Here is the answer.
File.open("file.txt", "r").each_line do |line|
if line =~ /minor mistakes/
puts "Hello, how are you ?"
end
puts "#{line}"
end
Here is ruby one-liner.
ruby -pe 'puts "Hello, how are you ?" if $_ =~ /minor mistakes/' < file.txt
You can find this functionality in a gem like Thor. Check out the documentation for the inject_into_file method here:
http://www.rubydoc.info/github/erikhuda/thor/master/Thor/Actions#inject_into_file-instance_method.
Here is the source code for the method:
https://github.com/erikhuda/thor/blob/067f6638f95bd000b0a92cfb45b668bca5b0efe3/lib/thor/actions/inject_into_file.rb#L24-L32
If you wish to match on line n (offset from zero):
def match_line_i(fname, linenbr regex)
IO.foreach(fname).with_index { |line,i|
return line[regex] if i==line_nbr }
end
or
return scan(regex) if i==line_nbr }
depending on your requirements.
If you wish to match on a given line, then return the previous line, for application of gsub (or whatever):
def return_previous_line(fname, regex)
last_line = nil
IO.foreach(fname) do |line|
line = f.readline
return last_line if line =~ regex
last_line = line
end
end
Both methods return nil if there is no match.
Okay, as there is no such option available with sub/gsub, I am pasting here my code (with slight modifications to BMW's code) for all three options. Hopefully, this helps someone in a similar situation.
Insert text before a pattern
Insert text after a pattern
Insert text at a specific line number
root#box27:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
correct minor mistakes
add related resources or links
always respect the original author
root#box27:~#
root#box27:~# cat ruby_script
puts "#### Insert text before a pattern"
pattern = 'minor mistakes'
File.open("file.txt", "r").each_line do |line|
puts "Hello, how are you ?" if line =~ /#{pattern}/
puts "#{line}"
end
puts "\n\n#### Insert text after a pattern"
pattern = 'meaning without'
File.open("file.txt", "r").each_line do |line|
found = 'no'
if line =~ /#{pattern}/
puts "#{line}"
puts "Hello, how are you ?"
found = 'yes'
end
puts "#{line}" if found == 'no'
end
puts "\n\n#### Insert text at a particular line"
insert_at_line = 3
line_number = 1
File.open("file.txt", "r").each_line do |line|
puts "Hello, how are you ?" if line_number == insert_at_line
line_number += 1
puts "#{line}"
end
root#box27:~#
How can I delete a single, specific line from a text file? For example the third line, or any other line. I tried this:
line = 2
file = File.open(filename, 'r+')
file.each { last_line = file.pos unless file.eof? }
file.seek(last_line, IO::SEEK_SET)
file.close
Unfortunately, it does nothing. I tried a lot of other solutions, but nothing works.
I think you can't do that safely because of file system limitations.
If you really wanna do a inplace editing, you could try to write it to memory, edit it, and then replace the old file. But beware that there's at least two problems with this approach. First, if your program stops in the middle of rewriting, you will get an incomplete file. Second, if your file is too big, it will eat your memory.
file_lines = ''
IO.readlines(your_file).each do |line|
file_lines += line unless <put here your condition for removing the line>
end
<extra string manipulation to file_lines if you wanted>
File.open(your_file, 'w') do |file|
file.puts file_lines
end
Something along those lines should work, but using a temporary file is a much safer and the standard approach
require 'fileutils'
File.open(output_file, "w") do |out_file|
File.foreach(input_file) do |line|
out_file.puts line unless <put here your condition for removing the line>
end
end
FileUtils.mv(output_file, input_file)
Your condition could be anything that showed it was the unwanted line, like, file_lines += line unless line.chomp == "aaab" for example, would remove the line "aaab".
I was trying to use the following code to read lines from a file. But when reading a file, the contents are all in one line:
line_num=0
File.open('xxx.txt').each do |line|
print "#{line_num += 1} #{line}"
end
But this file prints each line separately.
I have to use stdin, like ruby my_prog.rb < file.txt, where I can't assume what the line-ending character is that the file uses. How can I handle it?
Ruby does have a method for this:
File.readlines('foo').each do |line|
puts(line)
end
http://ruby-doc.org/core-1.9.3/IO.html#method-c-readlines
File.foreach(filename).with_index do |line, line_num|
puts "#{line_num}: #{line}"
end
This will execute the given block for each line in the file without slurping the entire file into memory. See: IO::foreach.
I believe my answer covers your new concerns about handling any type of line endings since both "\r\n" and "\r" are converted to Linux standard "\n" before parsing the lines.
To support the "\r" EOL character along with the regular "\n", and "\r\n" from Windows, here's what I would do:
line_num=0
text=File.open('xxx.txt').read
text.gsub!(/\r\n?/, "\n")
text.each_line do |line|
print "#{line_num += 1} #{line}"
end
Of course this could be a bad idea on very large files since it means loading the whole file into memory.
Your first file has Mac Classic line endings (that’s "\r" instead of the usual "\n"). Open it with
File.open('foo').each(sep="\r") do |line|
to specify the line endings.
I'm partial to the following approach for files that have headers:
File.open(file, "r") do |fh|
header = fh.readline
# Process the header
while(line = fh.gets) != nil
#do stuff
end
end
This allows you to process a header line (or lines) differently than the content lines.
It is because of the endlines in each lines.
Use the chomp method in ruby to delete the endline '\n' or 'r' at the end.
line_num=0
File.open('xxx.txt').each do |line|
print "#{line_num += 1} #{line.chomp}"
end
how about gets ?
myFile=File.open("paths_to_file","r")
while(line=myFile.gets)
//do stuff with line
end
Don't forget that if you are concerned about reading in a file that might have huge lines that could swamp your RAM during runtime, you can always read the file piece-meal. See "Why slurping a file is bad".
File.open('file_path', 'rb') do |io|
while chunk = io.read(16 * 1024) do
something_with_the chunk
# like stream it across a network
# or write it to another file:
# other_io.write chunk
end
end
How do I make \n actually work in my output? At the moment it just writes it all in 1 long block. Thanks for any help
Dir.chdir 'C:/Users/name/Music'
music = Dir['C:/Users/name/Music/*.{mp3, MP3}']
puts 'what would you like to call the playlist?'
#new = ''
playlist_name = gets.chomp + '.m3u'
music.each do |z|
#new += z + '\n'
end
File.open playlist_name, 'w' do |f|
f.write #new
end
Use "\n" instead of '\n'
I would like to share my experience with \n
I came to notice that "\n" works as-
puts "\n\n" // to provide 2 new lines
but not
p "\n\n"
also
puts '\n\n'
Doesn't works.
Hope will work for you!!
You can do this all in the File.open block:
Dir.chdir 'C:/Users/name/Music'
music = Dir['C:/Users/name/Music/*.{mp3, MP3}']
puts 'what would you like to call the playlist?'
playlist_name = gets.chomp + '.m3u'
File.open playlist_name, 'w' do |f|
music.each do |z|
f.puts z
end
end
Actually you don't even need the block:
Dir.chdir 'C:/Users/name/Music'
music = Dir['C:/Users/name/Music/*.{mp3, MP3}']
puts 'what would you like to call the playlist?'
playlist_name = gets.chomp + '.m3u'
File.open(playlist_name, 'w').puts(music)
For me it didn't work with adding "\n" to the end of an existing argument to puts, so as a workaround I called print on the next line with "\n" as an argument, although I suppose I could have just called puts again.
This did not produce the desired result:
puts "Coach says: #{coach_answer(user_input)}\n"
But this did:
puts "Coach says: #{coach_answer(user_input)}"
print "\n"