Ruby command Line options

Hi,

Can you bit help me to understand how the below options work in real
life?

-T [level]

-K [ kcode]

-F pat

-i [ ext]

Thanks in advance!

http://www.tutorialspoint.com/ruby/ruby_command_line_options.htm

To the best of my knowledge (someone please correct me if I’m wrong)

-T: Sets a level that determines how “paranoid” it should be about
“tainted” input. You can use this to avoid users keying in malicious
input. I think it’s mainly used when you’re running “eval” statements on
user input.

-K: Determines what kind of character set you’re using. Some characters
may not be valid if you’re using the wrong set.

-F: Never used this but according to the above link it just lets you
specify the default seperator when using the “split” method.

-i: looks like you can specify a file to output to. Not so sure about
this one.

On Fri, 11 Jan 2013 13:03:28 +0100, Arup R. [email protected]
wrote:

Hi,

Can you bit help me to understand how the below options work in real
life?

-T [level]

This one controls tainting, which is a bolted-on feature that no one
ever uses as far as I know. It is supposed to help prevent security
holes, but like PHP’s magic_quotes isn’t a real solution.

-K [ kcode]

I think this is 1.8 only (or at least I can’t find it in Ruby 1.9’s
ruby -h output). It was something encoding-related.

-F pat

-i [ ext]

These would generally be used with -e, for one-off magic one-liners. You
probably won’t find them in real life code either.

Try this: http://www.ruby-doc.org/docs/ProgrammingRuby/html/taint.html

Joel P. wrote in post #1091897:

http://www.tutorialspoint.com/ruby/ruby_command_line_options.htm

To the best of my knowledge (someone please correct me if I’m wrong)

-T: Sets a level that determines how “paranoid” it should be about
“tainted” input. You can use this to avoid users keying in malicious
input. I think it’s mainly used when you’re running “eval” statements on

Any small code snippet if you have, could you please share?

Thanks

Joel P. wrote in post #1091900:

Try this: http://www.ruby-doc.org/docs/ProgrammingRuby/html/taint.html

Joel, you are Awesome! Nice material you have posted. :slight_smile:

thanks as usual to you for your interest in my pain! :slight_smile:

Bartosz Dziewoński wrote in post #1091898:

On Fri, 11 Jan 2013 13:03:28 +0100, Arup R. [email protected]
wrote:

-F pat

-i [ ext]

Can any one help me to understand how the above two options work in
Ruby?

Thanks,

Eric C. wrote in post #1091980:

On Fri, Jan 11, 2013 at 12:07 PM, Arup R. [email protected]
wrote:

Ruby?

Excellent logic you just have provided to me!Exactly what or more than
what I was looking for.

Thank you very much!

On Fri, Jan 11, 2013 at 12:07 PM, Arup R. [email protected]
wrote:

Ruby?
They are all used primarily for one-liners (i.e. invocations where a
script is specified as a string on the command line after -e); the
switches in question closely mirror those present in perl, awk, and
sed.

-F is for use only with -a; -a in turn is for use only with -n or -p.

-n and -p take the script that’s the argument to -e and wrap it in a
loop. The loop is equivalent to while gets; <SCRIPT> end; the gets
puts the line read into the variable $. The difference between the
two is that -p prints each line read, while -n doesn’t. (Throught
experimentation, I just found out $
gets printed at the end of each
loop iteration; so if you modify $_ inside the loop, it will print the
modified version.)

-a causes Ruby to automatically split each line read into $_; the
result goes into $F, an array.

-F lets you specify the separator to be used by -a.

Thus, if we have a file foo:
foo:bar:foo

and we use the command line:
$ ruby -a -F: -n -e ‘p $F’ foo

we get the output:
[“foo”, “bar”, “foo\n”]

Now, -i is used to make changes to files supplied on the command line,
without having to code that specifically in the script. The argument
to -i specifies a filename extension to append to the filename(s), to
back up the old file(s). Thus if we have the above file foo and
another file named bar, with the contents:
bar:foo:bar

and we use the command line:
$ ruby -i~ -p -e “$_.gsub!(/bar/, ‘baz’)” foo bar

we will end up with these files:
foo~:
foo:bar:foo

bar~:
bar:foo:bar

foo:
foo:baz:foo

bar:
baz:foo:baz

ruby -h (at least in 1.9.3) implies that you can use -i without an
extension, in which case no backup will be made; but I can’t get it to
accept -i without an extension at the moment:

$ ruby -i -p -e “$_.gsub!(/bar/, ‘baz’)” foo bar
-e:1:in gets': Can't do inplace edit without backup (fatal) from -e:1:ingets’
from -e:1:in `’

Obviously though it’s a good idea to keep a backup.

On Fri, Jan 11, 2013 at 6:22 AM, Matma R. [email protected] wrote:

These would generally be used with -e, for one-off magic one-liners. You
probably won’t find them in real life code either.

My one-liners are my life :slight_smile:

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