I'm trying to access the original command line argument string in Ruby (ie - not using the pre-split/separated ARGV array). Does anyone know how to do this? For example:
$> ruby test.rb command "line" arguments
I want to be able to tell if 'line' had quotes around it:
"command \"line\" arguments"
Any tips? Thanks in advance
As far as I can tell, ruby is not removing those double-quotes from your command line. The shell is using them to interpolate the contents as a string and pass them along to ruby.
You can get everything that ruby receives like this:
cmd_line = "#{$0} #{ARGV.join( ' ' )}"
Why do you need to know what is in quotes? Can you use some other delimiter (like ':' or '#')?
If you need to, you can pass double-quotes to ruby by escaping them:
$> ruby test.rb command "\"line\"" arguments
The above cmd_line variable would receive the following string in that case:
test.rb comand "line" arguments
I think it's unlikely, as far as I know that's all dealt with by the shell before it gets passed to the program.
On Unix systems, the command line shell (Bash, csh, etc.) automatically converts such syntax into argument strings and sends them to the Ruby executable. For instance, * automatically expands to each file in a directory. I doubt there is a way to detect this, and I ask why you want to do so.
This should help:
cmdline = ARGV.map{|x| x.index(/\s/) ? "\"#{x}\"":x}.join " "
Since shell groups the words inside quotes into one argument, we need to check if each argument has whitespace in it, and if it does, put quotes around it.
It still won't preserve wildcards (*), env variables ($VAR), and other stuff that shell expands before passing it to your script.
To be able to pass a command as it is, without expansions, you'd have to resort to passing it in through IO, like echo "ls *" | my_script.rb
Ruby has a special module for this purpose.
http://ruby-doc.org/stdlib-1.9.3/libdoc/shellwords/rdoc/Shellwords.html
What you want is just:
require 'shellwords'
Shellwords.join ARGV[1..-1]
:p
Related
I am trying to give an argument to my python program through the terminal.
For this I am using the lines:
import sys
something = sys.argv[1]
I now try to put in a string like this through the bash terminal:
python my_script.py 2m+{N7HiwH3[>!"4y?t9*y#;/$Ar3wF9+k$[3hK/WA=aMzF°L0PaZTM]t*P|I_AKAqIb0O4# cm=sl)WWYwEg10DDv%k/"c{LrS)oVd§4>8bs:;9u$ *W_SGk3CXe7hZMm$nXyhAuHDi-q+ug5+%ioou.,IhC]-_O§V]^,2q:VBVyTTD6'aNw9:oan(s2SzV
This returns a bash error because some of the characters in the string are bash special characters.
How can I use the string exactly as it is?
You can put the raw string into a file, for example like this, with cat and a here document.
cat <<'EOF' > file.txt
2m+{N7HiwH3[>!"4y?t9*y#;/$Ar3wF9+k$[3hK/WA=aMzF°L0PaZTM]t*P|I_AKAqIb0O4# cm=sl)WWYwEg10DDv%k/"c{LrS)oVd§4>8bs:;9u$ *W_SGk3CXe7hZMm$nXyhAuHDi-q+ug5+%ioou.,IhC]-_O§V]^,2q:VBVyTTD6'aNw9:oan(s2SzV
EOF
and then run
python my_script.py "$(< file.txt)"
You can also use the text editor of your choice for the first step if you prefer that.
If this is a reoccurring task, which you have to perform from time to time, you can make your life easier with a little alias in your shell:
alias escape='read -r string ; printf "Copy this:\n%q\n" "${string}"'
It is using printf "%q" to escape your input string.
Run it like this:
escape
2m+{N7HiwH3[>!"4y?t9*y#;/$Ar3wF9+k$[3hK/WA=aMzF°L0PaZTM]t*P|I_AKAqIb0O4# cm=sl)WWYwEg10DDv%k/"c{LrS)oVd§4>8bs:;9u$ *W_SGk3CXe7hZMm$nXyhAuHDi-q+ug5+%ioou.,IhC]-_O§V]^,2q:VBVyTTD6'aNw9:oan(s2SzV
Copy this:
2m+\{N7HiwH3\[\>\!\"4y\?t9\*y#\;/\$Ar3wF9+k\$\[3hK/WA=aMzF°L0PaZTM\]t\*P\|I_AKAqIb0O4#\ cm=sl\)WWYwEg10DDv%k/\"c\{LrS\)oVd§4\>8bs:\;9u\$\ \*W_SGk3CXe7hZMm\$nXyhAuHDi-q+ug5+%ioou.\,IhC\]-_O§V\]\^\,2q:VBVyTTD6\'aNw9:oan\(s2SzV
You can use the escaped string directly in your shell, without additional quotes, like this:
python my_script.py 2m+\{N7HiwH3\[\>\!\"4y\?t9\*y#\;/\$Ar3wF9+k\$\[3hK/WA=aMzF°L0PaZTM\]t\*P\|I_AKAqIb0O4#\ cm=sl\)WWYwEg10DDv%k/\"c\{LrS\)oVd§4\>8bs:\;9u\$\ \*W_SGk3CXe7hZMm\$nXyhAuHDi-q+ug5+%ioou.\,IhC\]-_O§V\]\^\,2q:VBVyTTD6\'aNw9:oan\(s2SzV
In order to make life easier, shells like bash do a little bit of extra work to help users pass the correct arguments to the programs they instruct it to execute. This extra work usually results in predictable argument arrays getting passed to programs.
Oftentimes, though, this extra help results in unexpected arguments getting passed to programs; and sometimes results in the execution of undesired additional commands. In this case, though, it ended up causing Bash to emit an error.
In order to turn off this extra work, Bash allows users to indicate where arguments should begin and end by surrounding them by quotation marks. Bash supports both single quotes (') and double quotes (") to delimit arguments. As a last resort, if a string may contain single and double quotes (or double quotes are required but aren't aggressive enough), Bash allows you to indicate that a special- or whitespace-character should be part of the adjacent argument by preceding it with a backslash (\\).
If this method of escaping arguments is too cumbersome, it may be worth simplifying your program's interface by having it consume this data from a file instead of a command line argument. Another option is to create a program that loads the arguments from a more controlled location (like a file) and directly execs the target program with the desired argument array.
I am trying to study both bash and ruby and I am trying to pass a variable that contains a JSON object from ruby to be printed using a bash script.
I tried storing the JSON object in a variable then used that variable as an argument for my bash script but I am not getting the result that I wanted.
so in my ruby code I have this:
param = request.body
cmd = "ruby_to_bash #{param}"
exec cmd
and in my bash script, I am simply outputting the value of the argument:
echo $1
For example I have this JSON:
{"first":"one","second":"two","third":"three"}
my code only gives me this output:
{first:
I want to display the whole JSON object. How can I do this? Any kind of help will be much appreciated.
Both bash and ruby treat double quotes in a kinda special way: double-quoted strings are interpolated before passed to the receiver. I strongly encourage you to start with learning somewhat one in the first place instead of doing zero progress in both due to induced errors.
Answering the question stated, one must escape double quotes when passing back and forth since both ruby and bash treat them as content delimiters and discard when the content is already parsed in the resulting string.
This would work:
exec %|ruby_to_bash #{param.gsub('"', '\"')}|
I use %| and | as string delimiters to avoid clashes against inner quotes.
Sidenote: the above won’t work for the input containing spaces, but I purposely avoid to show how to deal with spaces since it leads to the dead end; once handled spaces with surrounding the interpolated param with single quotes, we are prone to be screwed up with inner single quotes in JSON object and so forth.
The code above is not someone should ever produce in production.
I think your best bet is, as usual in such cases, not to involve a shell at all.
When you say this:
cmd = "ruby_to_bash #{param}"
exec cmd
Your exec call is invoking a shell which parses cmd and then runs ruby_to_bash so you're doing this:
Build a command line.
Replace the current process with /bin/sh.
/bin/sh parses the command line that you should mashed together. This is where you need to worry about quoting and escaping to get past the shell.
/bin/sh exec's ruby_to_bash.
You could bypass the whole problem by using the multi-argument form of Kernel#exec:
exec(cmdname, arg1, ...)
command name and one or more arguments (no shell)
which doesn't bother with a shell at all. If you say:
exec 'ruby_to_bash', param
You won't involve a shell and the quotes or spacing in param won't matter to anyone other than ruby_to_bash.
I ham having difficulty understanding how to pass a variable to a ./configure command that includes variable expansion and quotes.
myvars.cfg
myFolderA="/home/myPrefix"
myFolderB="/home/stuffB"
myFolderC="/home/stuffC"
optsA="--prefix=${myFolderA}"
optsB="CPPFLAGS=\"-I${myFolderB} -I${myFolderC}\""
cmd="/home/prog/"
myScript.sh
#!/bin/bash
. /home/myvars.cfg
doCmd=("$cmd/configure" "${optsA}" "${optsB}")
${doCmd[#]}
The doCmd should look like this
/home/prog/configure --prefix=/home/myPrefix CPPFLAGS="-I/home/stuffB -I/home/stuffC"
however it seems when running bash it is adding single quotes
/home/prog/configure --prefix=/home/myPrefix 'CPPFLAGS="-I/home/stuffB' '-I/home/stuffC"'
causing an error of
configure: error: unrecognized option: `-I/home/stuffC"'
Is there a way to pass a variable that needs top be expanded and contains double quotes?
As your script is written, there is no point to using the doCmd array. You could simply write the command:
"$cmd/configure" "${optsA}" "${optsB}"
Or, more simply:
"$cmd/configure" "$optsA" "$optsB"
However, it is possible that you've simplified the script in a way which hides the need for the array. In any case, if you use the array, you need to ensure that its elements are not word-split and filepath expanded, so you must quote its expansion:
"${doCmd[#]}"
Also, you need to get rid of the quotes in optsB. You don't want to pass
CPPFLAGS="-I/home/stuffB -I/home/stuffC"
to the configure script. You want to pass what the shell would pass if you typed the above string. And what the shell would pass would be a single command-line argument with a space in it, looking like this:
CPPFLAGS=-I/home/stuffB -I/home/stuffC
In order to get that into optsB, you just write:
optsB="CPPFLAGS=-I${myFolderB} -I${myFolderC}"
Finally, the shell is not "adding single quotes" into the command line. It is showing you a form of the command whch you could type at the command-line. Since the argument (incorrectly) contains a quote symbol, the shell shows you the command with its arguments skingle-quoted, so that you can see that the optB has been (incorrectly) split into two arguments, each of which contains (incorrectly) one double quote.
You could have found much of the above and more by pasting your script into https://shellcheck.net. As the bash tag summary suggests, you should always try that before asking a shell question here because a lot of the time, it will solve your problem instantly.
There is a executbale called app, and it can take some options and command line args, -l -v, to name a few. Now I'm writing a bash script inside which app will be invoked with some options, and I did it this way,
opt_string="-l -v" # this string might change according to different conditions used in if-else
# HERE is my problem
./app ${opt_string}
Look how I invoked app, typically I just invoke it in prompt shell like this:
./app -l -v
But now in this script, would it be actually this:
./app "-l -v"
cuz ${opt_string} is a STRING quoted by "", if so I doubt whether app will run normally.
I know there might be a way around this by using eval "./app ${opt_string}", but is there any way to strip the ""?
BASH FAQ entry #50: "I'm trying to put a command in a variable, but the complex cases always fail!"
opt_string=(-l -v)
./app "${opt_string[#]}"
The way you're invoking (./app ${opt_string}) it is fine. You define opt_string as a single string because you quote the value in the assignment. However, when you dereference it, you have not used quotes, so the shell will substitute its value and then split it into individual words.
when you say
./app "$opt_string"
you are passing one single argument to the app. When you say
./app $opt_string
you are passing multiple arguments to the app.
See word splitting in the bash manual.
Note that braces are not quotes. Curly braces (in this context) merely serve to disambiguate the variable name from the surrounding text, i.e. echo "$opt_string_blah" versus echo "${opt_string}_blah"
I have a file located in the directory "C:\Documents and Settings\test.exe" but when I write the command `C:\Documents and Settings\test.exe in single qoutes(which I am not able to display in this box), used for executing the commands in Ruby, I am not able to do so and the error that I recieve is No file or Directory found. I have tried replacing "\" with "//" and "\" but nothing seems to work. I have also used system, IO.popen and exec commands but all efforts are in vain. Also exec commands makes the program to make an exit which I don't want to happen.
Thanks in advance.
The backtick environment is like double-quotes, so backslash are used for escaping. Further, Ruby will interpret the spaces as separating command-line arguments, so you need to quote the entire thing:
`"C:\\Documents and Settings\\test.exe"`
Another option is to use system and force a second argument. If system gets more than one argument, it treats the first argument as the path to the command to execute and you don't need to quote the command:
system('C:\Documents and Settings\test.exe','')
Note the use of single quotes, so we don't have escape the backslashes.
Of course, this won't get you the standard out/error, so if you are on Ruby 1.9.2, you can use the awesomely handy Open3 library, which works like system, but gives you more information about the process you just ran:
require 'open3'
stdout,stderr,status = Open3.capture3('C:\Documents and Settings\test.exe','')
puts stdout # => string containing standard output of your command
puts stderr # => string containing standard ERROR of your command
if status.success?
puts "It worked!"
else
puts "OH NOES! Got exit code #{status.exitstatus}"
end
`"C:\Documents and Settings\test.exe"`
or
`exec "C:\Documents and Settings\test.exe"`
or whatever in qoutes