How to read lines of a file in Ruby

Question

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  lt  file txt  where I can t assume what the line-ending character is that the file uses  How can I handle it

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

Ruby does have a method for this   File readlines  foo   each do  line    http   ruby-doc org core-1 9 3 IO html method-c-readlines

User · Answer

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

User · Answer

how about gets    myFile File open  paths to file   r   while line myFile gets     do stuff with line end

[ruby] How to read lines of a file in Ruby

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