使用popen执行命令

Question

I have a C++ program in which I want to execute the following command:

cmd = "(diff <(perl -ne 's/^\\S+\\s//; if ((/aaa/ .. /bbb/) && /ccc/)"
            " { print \"$_\"}' file1)"
            "<(perl -ne 's/^\\S+\\s//; if ((/aaa/ .. /bbb/) && /ccc/)"
            " { print \"$_\"} file2)) ";

I get this error when I want to execute this command:

Search pattern not terminated at -e line 1.

I've noticed that the following commands work like this:

cmd = "diff <(echo aa) <(echo bb)"
string strCall = "bash -c \"( " + cmd + " ) 2>&1\"";
stream = popen(strCall.c_str(),"r"); // doesn't work popen(**str**.c_str(),"r")

and an example perl command containing '"' works like this:

cmd = "perl -ne '{print \"$1\"}' file"
stream = popen(str.c_str(),"r"); // doesn't work  popen(**strCall**.c_str(),"r");

but if the perl command doesn't contains '"', it works both ways:

cmd = "perl -ne '{print $1}' file"
string strCall = "bash -c \"( " + cmd + " ) 2>&1\"";
stream = popen(str.c_str(),"r"); // also works popen(**strCall**.c_str(),"r");

How can I do to use both diff and perl in the same command. I assume I have to use strCall. I've tried also to escape the perl cmd like this, but it doesn't work:

cmd = "perl -ne '{print \\\"$1\\\"}' file" // one '/' for '/', one for "'" and one for '"'.

Also it didn't worked this, but I am however not allowed to use R("str"):

cmd = R"(perl -ne '{print \"$1\"}' file)"
string strCall = "bash -c \"( " + cmd + " ) 2>&1\"";
stream = popen(strCall.c_str(),"r")

Thanks.

Answer 1

I know I am not answering your question, but a common solution once you reach this many levels of quoting is to write a simple shell script and then call that from popen.

Eg, popen("/path/diffscript.sh", "r");