Unable to write to file... (example from "pickaxe book", second edition, p128)

ruby-talk
1

Following the example from "pickaxe book", second edition, p128

#!/usr/bin/ruby
File.open("testfile", "r") do |file|
  while line = file.gets
    puts line
  end
end

produces
copy.rb:2:in `initialize': No such file or directory - testfile (Errno::ENOENT)
        from copy.rb:2

···

--
John Maclean
MSc (DIC)
07739 171 531

2

The problem is clear. You are trying to read a file which does not exist. So,
to solve the `problem', you create a file named testfile, put some text in
it, and there you go,

···

On Thursday 19 January 2006 11:49, John Maclean wrote:

Following the example from "pickaxe book", second edition, p128

#!/usr/bin/ruby
File.open("testfile", "r") do |file|
  while line = file.gets
    puts line
  end
end

produces
copy.rb:2:in `initialize': No such file or directory - testfile
(Errno::ENOENT) from copy.rb:2

--
HT de Beer

3

John Maclean wrote:

Following the example from "pickaxe book", second edition, p128

#!/usr/bin/ruby File.open("testfile", "r") do |file|
  while line = file.gets
    puts line
  end
end

produces
copy.rb:2:in `initialize': No such file or directory - testfile (Errno::ENOENT)
        from copy.rb:2

John, you need the file named "testfile" to exist before you can run that code. It can't open a file if it doesn't exist!

Zach

4

Thanks! The light shines. So how can i -write- to a file using the code below as an example?

···

On Thu, 19 Jan 2006 19:56:55 +0900 zdennis <zdennis@mktec.com> wrote:

John Maclean wrote:
> Following the example from "pickaxe book", second edition, p128
>
> #!/usr/bin/ruby
> File.open("testfile", "r") do |file|
> while line = file.gets
> puts line
> end
> end
>
> produces
> copy.rb:2:in `initialize': No such file or directory - testfile (Errno::ENOENT)
> from copy.rb:2
>

John, you need the file named "testfile" to exist before you can run that code. It can't open a file
if it doesn't exist!

Zach

--
John Maclean
MSc (DIC)
07739 171 531

5

John Maclean escribió:

Thanks! The light shines. So how can i -write- to a file using the code below as an example?

Change
>>> File.open("testfile", "r") do |file|
to
>>> File.open("testfile", "w") do |file|

Read:
http://www.ruby-doc.org/core/classes/File.html
http://www.ruby-doc.org/core/classes/IO.html

Diego

···

On Thu, 19 Jan 2006 19:56:55 +0900 > zdennis <zdennis@mktec.com> wrote:

John Maclean wrote:

Following the example from "pickaxe book", second edition, p128

#!/usr/bin/ruby File.open("testfile", "r") do |file|
  while line = file.gets
    puts line
  end
end

produces
copy.rb:2:in `initialize': No such file or directory - testfile (Errno::ENOENT)
        from copy.rb:2

John, you need the file named "testfile" to exist before you can run that code. It can't open a file if it doesn't exist!

Zach

6

Well you need more than that. For one thing the file.gets will fail if
file was opened in write mode. Also the puts is going to STDOUT, not
the file. You probably want something like this:

#!/usr/bin/ruby
File.open("testfile", "w") do |file|
  while line = gets
    file.puts line
  end
end

This will get input from STDIN and write it out to test file. Program
terminates on EOF marker (CTRL-D when run interactively).

Jacob Fugal

···

On 1/19/06, Diego Algorta Casamayou <ruby@dac.e4ward.com> wrote:

Change
>>> File.open("testfile", "r") do |file|
to
>>> File.open("testfile", "w") do |file|

7

John Maclean wrote:

Thanks! The light shines. So how can i -write- to a file using the code
below as an example?

Open a file for writing

File.open( "infile", "r" ) | in |
  File.open( "outfile", "w" ) | out |
    while line = in.gets
      out.print line
    end
  end
end

See the docs for IO which explain all the mode flags ("r", "w", "a",
etc.).

···

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8

Jacob Fugal escribió:

···

On 1/19/06, Diego Algorta Casamayou <ruby@dac.e4ward.com> wrote:

Change
>>> File.open("testfile", "r") do |file|
to
>>> File.open("testfile", "w") do |file|

Well you need more than that. For one thing the file.gets will fail if
file was opened in write mode. Also the puts is going to STDOUT, not
the file. You probably want something like this:

#!/usr/bin/ruby
File.open("testfile", "w") do |file|
  while line = gets
    file.puts line
  end
end

This will get input from STDIN and write it out to test file. Program
terminates on EOF marker (CTRL-D when run interactively).

That's right. I focused my reply on on the open method, but missed the full example.

Diego

9

Mike Fletcher wrote:

John Maclean wrote:

Thanks! The light shines. So how can i -write- to a file using the code
below as an example?

Open a file for writing

File.open( "infile", "r" ) | in |
  File.open( "outfile", "w" ) | out |
    while line = in.gets
      out.print line
    end
  end
end

See the docs for IO which explain all the mode flags ("r", "w", "a",
etc.).

Do you think this script work?

Li

···

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10

It fails because "in" is a reserved word in Ruby and cannot be used as
a variable name. Try changing the two instances of "in" to "inp" and
it will work.

···

On 03/11/06, Li Chen <chen_li3@yahoo.com> wrote:

Mike Fletcher wrote:
> John Maclean wrote:
> [snip]
>
> File.open( "infile", "r" ) | in |
> File.open( "outfile", "w" ) | out |
> while line = in.gets
> out.print line
> end
> end
> end

Do you think this script work?

--
Marcel

11

Li Chen wrote:

Mike Fletcher wrote:

John Maclean wrote:

Thanks! The light shines. So how can i -write- to a file using the code
below as an example?

Open a file for writing

File.open( "infile", "r" ) | in |
  File.open( "outfile", "w" ) | out |
    while line = in.gets
      out.print line
    end
  end
end

See the docs for IO which explain all the mode flags ("r", "w", "a",
etc.).

Do you think this script work?

As is no (I blame lack of caffeine and/or sleep); but with "do" inserted
in the right two places and the reserved word "in" replaced with
something that's not a reserved word ( say "inf" ) it works just fine.

One should take all example code posted in haste to mailing lists with a
grain of salt.

···

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