I'm looking a way to compile Ruby code on OSX. I am using MacVim, and my code says:
puts "test"
I type rubydo %, and I get an error message SyntaxError: eval:1: unterminated quoted string meets end of file. What am I doing wrong?
Vim's rubydo command executes a command. You may have thought it was a filename (and used "%" as the parameter, i.e., the current buffer). The % is ruby's alternate string delimiter, and depending on how rubydo is implemented, the bare "%" could be mistaken for the beginning of a string.
The % Notation (Ruby Programming)
Vim documentation: if_ruby
Related
I need to parse a basename in ruby a from file path which I get as input. Unix format works fine on Linux.
File.basename("/tmp/text.txt")
return "text.txt".
However, when I get input in windows format:
File.basename("C:\Users\john\note.txt")
or
File.basename("C:\\Users\\john\\note.txt")
"C:Usersjohn\note.txt" is the output (note that \n is a new line there), but I didn't get "note.txt".
Is there some nice solution in ruby/rails?
Solution:
"C:\\test\\note.txt".split(/\\|\//).last
=> "note.txt"
"/tmp/test/note.txt".split(/\\|\//).last
=> "note.txt"
If the Linux file name doesn't contain \, it will work.
Try pathname:
require 'pathname'
Pathname.new('C:\Users\john\note.txt').basename
# => #<Pathname:note.txt>
Pathname docs
Ref How to get filename without extension from file path in Ruby
I'm not convinced that you have a problem with your code. I think you have a problem with your test.
Ruby also uses the backslash character for escape sequences in strings, so when you type the String literal "C:\Users\john\note.txt", Ruby sees the first two backslashes as invalid escape sequences, and so ignores the escape character. \n refers to a newline. So, to Ruby, this literal is the same as "C:Usersjohn\note.txt". There aren't any file separators in that sequence, since \n is a newline, not a backslash followed by the letter n, so File.basename just returns it as it receives it.
If you ask for user input in either a graphical user interface (GUI) or command line interface (CLI), the user entering input needn't worry about Ruby String escape sequences; those only matter for String literals directly in the code. Try it! Type gets into IRB or Pry, and type or copy a file path, and press Enter, and see how Ruby displays it as a String literal.
On Windows, Ruby accepts paths given using both "/" (File::SEPARATOR) and "\\" (File::ALT_SEPARATOR), so you don't need to worry about conversion unless you are displaying it to the user.
Backslashes, while how Windows expresses things, are just a giant nuisance. Within a double-quoted string they have special meaning so you either need to do:
File.basename("C:\\Users\\john\\note.txt")
Or use single quotes that avoid the issue:
File.basename('C:\Users\john\note.txt')
Or use regular slashes which aren't impacted:
File.basename("C:/Users/john/note.txt")
Where Ruby does the mapping for you to the platform-specific path separator.
In Vim, I can echo the current filename using this command:
:echo #%
I found that information here: http://vim.wikia.com/wiki/Get_the_name_of_the_current_file
Can someone explain why the # symbol is necessary? If I enter the command without the # symbol, I get an error:
E15: Invalid expression: %
E15: Invalid expression: %
However, if I try to send the filename to a bang command as an argument, including the # sign appears as a regular character in the argument. Removing the # sign works. In other words, in my .bash_profile I have the following function:
test_func() {
echo $1
}
In Vim, I run:
:! test_func #% #outputs #path/to/my/file
:! test_func % #outputs path/to/my/file
What is the # symbol doing and why does it behave differently when sending the output to a bash function?
:echo takes a Vimscript expression, whereas :! takes and external command, which is a special case for a filename, which is accepted by :edit et al.
For external commands and filenames, there are special characters such as % and #, described under :help cmdline-special. This also includes this crucial sentence:
In Ex commands, at places where a file name can be used, the following
characters have a special meaning.
In contrast, :echo does not take a filename, but an expression. There are several ways to resolve the current filename; the most direct is via expand():
:echo expand('%')
Alternatively, as the current filename is also stored in a special register %, and registers are addressed via the # sigil:
:echo #%
The other way around
This also explains the frequent question of why :edit g:variable doesn't work as expected. Vim's evaluation rules are different than most programming languages. You need to use :execute in order to evaluate a variable (or expression); otherwise, it's taken literally; i.e. Vim uses the variable name itself as the argument.
I believe that is :h expr-register:
register expr-register #r
#r contents of register 'r'
The result is the contents of the named register, as a single string.
Newlines are inserted where required. To get the contents of the unnamed
register use #" or ##. See |registers| for an explanation of the available
registers.
When using the '=' register you get the expression itself, not what it
evaluates to. Use |eval()| to evaluate it.
As to why you don't need that for :! that is probably because of :h cmdline-special.
Ex special characters cmdline-special
Note: These are special characters in the executed command line. If you want
to insert special things while typing you can use the CTRL-R command. For
example, "%" stands for the current file name, while CTRL-R % inserts the
current file name right away. See |c_CTRL-R|.
Note: If you want to avoid the special characters in a Vim script you may want
to use |fnameescape()|.
In Ex commands, at places where a file name can be used, the following
characters have a special meaning. These can also be used in the expression
function expand() |expand()|.
% Is replaced with the current file name. :_% c_%
I've been learning about remote/arbitrary command execution. In doing so, I came across some Ruby I thought would be fun to try and exploit.
I've been somewhat successful as I managed to get it to run the 'ls' command, but I can't work out how to add space characters into my commands. If I add a space in, the parse method that URI calls throws an exception.
Here's the code I was trying to exploit:
injection = "www.google.com';ls;#"
require 'uri'
URI.parse(injection)
puts `curl '#{injection}'`
So your challenge, should you choose to accept it, is to run an 'ls -l' command instead of 'ls' by only changing the injection string. You may not change anything but the first line.
Things I've tried:
ls%2f-l - # Doesn't raise an exception but unix doesn't unescape CGI encodings.
ls\x20-l - # Raises an exception because Ruby parses the UTF-8.
# Other various escape combinations (\\x20, etc)
Maybe it's not possible?
Thanks
You can use the Internal Field Separator (<space><tab><newline>). Since this is what the shell separates with anyway, it will accept it as a separator.
injection = "www.google.com';ls$IFS-l;#"
(BTW, thanks for a nice Saturday night puzzle.)
Is - it's possible. Just put your string in quotes:
1) from a command prompt:
two strings # No quote: the shell sees two strings
"one string" # with single (') or double quotes (") the shell sees only one string
2) from a string literal
mystring = "\"this will be interpreted as one string\"";
my Question is how I can convert the STDIN of cmd ARGV or gets from hex to ascii
I know that if I assigned hex string to variable it'll be converted once I print it
ex
hex_var = "\x41\41\x41\41"
puts hex_var
The result will be
AAAA
but I need to get the value from command line by (ARGV or gets)
say I've this lines
s = ARGV
puts s
# another idea
puts s[0].gsub('x' , '\x')
then I ran
ruby gett.rb \x41\x41\x41\x41
I got
\x41\x41\x41\x41
is there a way to get it work ?
There are a couple problems you're dealing with here. The first you've already tried to address, but I don't think your solution is really ideal. The backslashes you're passing in with the command line argument are being evaluated by the shell, and are never making it to the ruby script. If you're going to simply do a gsub in the script, there's no reason to even pass them in. And doing it your way means any 'x' in the arguments will get swapped out, even those that aren't being used to indicate a hex. It would be better to double escape the \ in the argument if possible. Without context of where the values are coming from, it's hard to say with way would actually be better.
ruby gett.rb \\x41\\x41
That way ARGV will actually get '\x41\x41', which is closer to what you want.
It's still not exactly what you want, though, because ARGV arguments are created without expression substitution (as though they are in single quotes). So Ruby is escaping that \ even though you don't want it to. Essentially you need to take that and re-evaluate it as though it were in double quotes.
eval('"%s"' % s)
where s is the string.
So to put it all together, you could end up with either of these:
# ruby gett.rb \x41\x41
ARGV.each do |s|
s = s.gsub('x' , '\x')
p eval('"%s"' % s)
end
# => "AA"
# ruby gett.rb \\x41\\x41
ARGV.each do |s|
p eval('"%s"' % s)
end
# => "AA"
Backlashes entered in the console will be interpreted by the shell and will
not make it into your Ruby script, unless you enter two backlashes in a row,
in which case you script will get a literal backlash and no automatic
conversion of hexadecimal character codes following those backlashes.
You can convert these escaped codes to characters manually if you replace the last line of your script with this:
puts s.gsub(/\\x([[:xdigit:]]{1,2})/) { $1.hex.chr }
Then run it with double backlashed input:
$ ruby gett.rb \\x41\\x42\\x43
ABC
When fetching user input through gets or similar, only a single backslash will be need to be entered by the user for each character escape, since that will indeed be passed to your script as literal backslashes and thus handled correctly by the above gsub call.
An alternative way when parsing command line arguments would be to let the shell interpret the character escapes for you. How to do this will depend on what shell you are using. If using bash, it can be done
like this:
$ echo $'\x41\x42\x43'
ABC
$ ruby -e 'puts ARGV' $'\x41\x42\x43'
ABC
In the Ruby string :
"${0} ${1} ${2:hello}"
is ${i} the ith argument in the command that called this particular file.
Tried searching the web for "Ruby ${0}" however the search engines don't like non-alphanumeric characters.
Consulted a Ruby book which says #{...} will substitute the results of the code in the braces, however this does not mention ${...}, is this a special syntax to substitute argvalues into a string, thanks very much,
Joel
As mentioned above ${0} will do nothing special, $0 gives the name of the script, $1 gives the first match from a regular expression.
To interpolate a command line argument you'd normally do this:
puts "first argument = #{ARGV[0]}"
However, ARGV is also aliased as $* so you could also write
puts "first argument = #{$*[0]}"
Perhaps that's where the confusion arose?