quoting and escaping (commandline and args)

[user706]

Hi,

how can one get the quoting and escaping right, when one wants to issue complex command-lines?

Here are examples:

a)

/bin/bash -c 'set -Eeuo pipefail ; trap "trap - SIGTERM && echo \"killing -$$\" && kill -- -$$" SIGINT SIGTERM EXIT; echo "pid $$" ; sleep 1; echo "done"'

equiv with the following (but now using only double-quotes)

b)

/bin/bash -c "set -Eeuo pipefail ; trap \"trap - SIGTERM && echo \\\"killing -\$\$\\\" && kill -- -\$\$\" SIGINT SIGTERM EXIT; echo \"pid \$\$\" ; sleep 1; echo \"done\""

equiv with

a2)

eval "/bin/bash -c 'set -Eeuo pipefail ; trap \"trap - SIGTERM && echo \\\"killing -\$\$\\\" && kill -- -\$\$\" SIGINT SIGTERM EXIT; echo \"pid \$\$\" ; sleep 1; echo \"done\"'"

equiv with

b2)

eval "/bin/bash -c \"set -Eeuo pipefail ; trap \\\"trap - SIGTERM && echo \\\\\\\"killing -\\\$\\\$\\\\\\\" && kill -- -\\\$\\\$\\\" SIGINT SIGTERM EXIT; echo \\\"pid \\\$\\\$\\\" ; sleep 1; echo \\\"done\\\"\""

How does one construct those command-lines above, for boost.process??

If I copy/paste the above commands in bash, I get this output:

pid 20906
done
killing -20906
Terminated               // this line (and line above this one) is printed because of EXIT in the command (removing EXIT, will result in TERMINATED not being printed

More easily readable, I basically want to have /bin/bash execute the following:

set -Eeuo pipefail
trap "trap - SIGTERM && echo \"killing -$$\" && kill -- -$$" SIGINT SIGTERM EXIT
echo "pid $$"
sleep 1
echo "done"

Thanks!

[user706]

Perhaps like this:

#include <boost/process.hpp>

#include <string>
#include <iostream>
#include <chrono>
#include <thread>

int main()
{
    namespace bp = boost::process;
    bp::group g;
//  bp::child c(        "/bin/bash",           "-c",  "set -Eeuo pipefail ; trap \"trap - SIGTERM && echo \\\"killing -$$\\\" && kill -- -$$\" SIGINT SIGTERM EXIT; echo \"pid $$\" ; sleep 1; echo \"done\"" , g);
    bp::child c(bp::exe="/bin/bash", bp::args={"-c",  "set -Eeuo pipefail ; trap \"trap - SIGTERM && echo \\\"killing -$$\\\" && kill -- -$$\" SIGINT SIGTERM EXIT; echo \"pid $$\" ; sleep 1; echo \"done\""}, g);
    //                                                ^^^^^^^...
    //                                                same as b) above; except: here we do not escape $:   so instead of \$   we use $
    
    std::cout << "\tNote: c.id() == " << c.id() << std::endl;
    
    std::this_thread::sleep_for(std::chrono::milliseconds{100});
    //::kill(-c.id(), SIGTERM);
    //::kill(-c.id(), SIGINT);
    
    c.wait();
}

How would one do it in a single string (instead of splitting into "/bin/bash", "-c", "...") ? Is that possible?