Double quotes embedded in a string

Here is something that I am struggling with – I would like to execute a
command string with an IO.popen call that contains embedded double quote
characters. When I build the initial command string everything seems to
work, but once I pass is on to IO.popen, it seems to mess up the double
quotes.

Here is my example, I want to execute the following command from a Ruby
program:

 pppd connect "chat -v '' ATZ OK ATDT5551234 CONNECT '' ogin:

username word: password" /dev/ttyS0 115200 -detach crtscts modem
defaultroute

I create the command string by the long and somewhat ugly ruby command:

 command = "pppd connect \\\"chat -v '' #{initialization_command}

#{initialization_response} #{dial_command} #{dial_response} ‘’
#{username_prompt} #{username} #{password_prompt} #{password}\"
#{device.name} #{speed} -detach crtscts modem defaultroute\r\n"

In this case, I escaped the escaped the double quote. I have also tried
various combinations of multiple double quotes (4 in a row, etc.).

If I now echo the command using a system call:

 system( "echo #{command}" )

the command seems to echo the desired result:

 pppd connect "chat -v  ATZ OK ATD5551234 CONNECT  ogin: username

word: password" /dev/ttyS0 115200 -detach crtscts modem defaultroute

But when I pass it to IO.popen, I get

 pppd: unrecognized option '-v'
 pppd version 2.4.1
   Usage: pppd [ options ], where options are:
         <device>        Communicate over the named device
         <speed>         Set the baud rate to <speed>
         <loc>:<rem>     Set the local and/or remote interface IP
                         addresses.  Either one may be omitted.
         asyncmap <n>    Set the desired async map to hex <n>
         auth            Require authentication from peer
         connect <p>     Invoke shell command <p> to set up the

serial line
crtscts Use hardware RTS/CTS flow control
defaultroute Add default route through interface
file Take options from file
modem Use modem control lines
mru Set MRU value to for negotiation
See pppd(8) for more options.

which is caused by that the double quotes are being stripped by
IO.popen. How do I avoid this?

Thanks,
Dale M.

On Sat, 29 Jul 2006, Dale M. wrote:

username word: password" /dev/ttyS0 115200 -detach crtscts modem defaultroute

I create the command string by the long and somewhat ugly ruby command:

command = "pppd connect \\\"chat -v '' #{initialization_command}

#{initialization_response} #{dial_command} #{dial_response} ‘’
#{username_prompt} #{username} #{password_prompt} #{password}\"
#{device.name} #{speed} -detach crtscts modem defaultroute\r\n"

use this

cmd = %W[
pppd connect

 "
   chat -v ''
   #{ initialization_command }
   #{ initialization_response }
   #{ dial_command }
   #{ dial_response }
   ''
   #{ username_prompt }
   #{ username }
   #{ password_prompt }
   #{ password }
 "

 #{ device.name } #{ speed } -detach crtscts modem defaultroute

].join.strip

In this case, I escaped the escaped the double quote. I have also tried
various combinations of multiple double quotes (4 in a row, etc.).

using %W or %Q is the way to go.

If I now echo the command using a system call:

system( "echo #{command}" )

the command seems to echo the desired result:

pppd connect "chat -v  ATZ OK ATD5551234 CONNECT  ogin: username

word: password" /dev/ttyS0 115200 -detach crtscts modem defaultroute

becuase you running it via the shell - to whom your ‘’ mean something.

But when I pass it to IO.popen, I get

you bypass the shell. so you calling the pppd program with the
following
elements of argv

argv[1] = connect
argv[2] = "chat
argv[3] = -v
argv[4] = ‘’
argv[5] = ATZ

so there are all sorts of problems - you are losing the word
splitting/grouping that sh/bash normally does to your command, so you
lose
your big double quoted string. you are also losing your empty strings
since
bash doesn’t get to take a whack at those you are passing two single
quote
marks instead.

you can try to build up the command yourself - or you can just let
bash/sh do
it for you: assume you build the command as above, then just let sh
execute it
for you like so

stdout =
IO.popen(‘sh’,‘r+’) do |sh|
sh.puts cmd
sh.close_write
sh.read
end

which is caused by that the double quotes are being stripped by
IO.popen. How do I avoid this?

just to clarify. it’s not that IO.popen stripes double quotes, it’s
that bash
has not interpreted them.

regards.

-a

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