The difference is that recv()/send() work only on socket descriptors and let you specify certain options for the actual operation. Those functions are slightly more specialized (for instance, you can set a flag to ignore SIGPIPE, or to send out-of-band messages…). Functions read()/write() are the universal file descriptor functions working on all descriptors.
mmap is great if you have multiple processes accessing data in a read only fashion from the same file, which is common in the kind of server systems I write. mmap allows all those processes to share the same physical memory pages, saving a lot of memory. mmap also allows the operating system to optimize … Read more
>> /dev/null redirects standard output (stdout) to /dev/null, which discards it. (The >> seems sort of superfluous, since >> means append while > means truncate and write, and either appending to or writing to /dev/null has the same net effect. I usually just use > for that reason.) 2>&1 redirects standard error (2) to standard … Read more
#include <cstdio> #include <iostream> #include <memory> #include <stdexcept> #include <string> #include <array> std::string exec(const char* cmd) { std::array<char, 128> buffer; std::string result; std::unique_ptr<FILE, decltype(&pclose)> pipe(popen(cmd, “r”), pclose); if (!pipe) { throw std::runtime_error(“popen() failed!”); } while (fgets(buffer.data(), buffer.size(), pipe.get()) != nullptr) { result += buffer.data(); } return result; } Pre-C++11 version: #include <iostream> #include <stdexcept> #include … Read more
Use pkill -f, which matches the pattern for any part of the command line pkill -f my_pattern Just in case it doesn’t work, try to use this one as well: pkill -9 -f my_pattern
POSIX is a family of standards, specified by the IEEE, to clarify and make uniform the application programming interfaces (and ancillary issues, such as commandline shell utilities) provided by Unix-y operating systems. When you write your programs to rely on POSIX standards, you can be pretty sure to be able to port them easily among … Read more
set -x or set -o xtrace expands variables and prints a little + sign before the line. set -v or set -o verbose does not expand the variables before printing. Use set +x and set +v to turn off the above settings. On the first line of the script, one can put #!/bin/sh -x (or … Read more