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cpp:pipe [2019-05-28 15:26] |
cpp:pipe [2020-02-15 00:57] (current) |
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| + | =====Unix execute command with redirect std input/output to pipes.===== | ||
| + | |||
| + | "Yet another" variant of classic algorithm. =) | ||
| + | |||
| + | <code c++ pipe.cpp> | ||
| + | /* | ||
| + | * pipe.cpp | ||
| + | * | ||
| + | * Copyright 2004-2019 Oleg Borodin <borodin@unix7.org> | ||
| + | * | ||
| + | * This program is free software; you can redistribute it and/or modify | ||
| + | * it under the terms of the GNU General Public License as published by | ||
| + | * the Free Software Foundation; either version 2 of the License, or | ||
| + | * (at your option) any later version. | ||
| + | * | ||
| + | * This program is distributed in the hope that it will be useful, | ||
| + | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| + | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| + | * GNU General Public License for more details. | ||
| + | * | ||
| + | * You should have received a copy of the GNU General Public License | ||
| + | * along with this program; if not, write to the Free Software | ||
| + | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, | ||
| + | * MA 02110-1301, USA. | ||
| + | */ | ||
| + | |||
| + | #include <iostream> | ||
| + | |||
| + | namespace unistd { | ||
| + | #include <unistd.h> | ||
| + | #include <sys/wait.h> | ||
| + | } | ||
| + | |||
| + | std::string execv3(const std::string& cmd, const std::string& msg = "") { | ||
| + | std::string result = ""; | ||
| + | |||
| + | const int pipeout = 1; | ||
| + | const int pipein = 0; | ||
| + | |||
| + | int pipe_out[2]; | ||
| + | int pipe_in[2]; | ||
| + | |||
| + | if (unistd::pipe(pipe_out) < 0) { | ||
| + | return result; | ||
| + | } | ||
| + | if (unistd::pipe(pipe_in) < 0) { | ||
| + | return result; | ||
| + | } | ||
| + | |||
| + | pid_t pid = unistd::fork(); | ||
| + | if (pid < 0) { | ||
| + | return result; | ||
| + | } | ||
| + | // child process | ||
| + | if (pid == 0) { | ||
| + | // close unised ends and reasign std in/out | ||
| + | unistd::close(pipe_out[pipein]); | ||
| + | unistd::dup2(pipe_out[pipeout], fileno(stdout)); | ||
| + | |||
| + | unistd::close(pipe_in[pipeout]); | ||
| + | unistd::dup2(pipe_in[pipein], fileno(stdin)); | ||
| + | |||
| + | unistd::execl(cmd.c_str(), cmd.c_str(), NULL); | ||
| + | |||
| + | unistd::close(pipe_out[pipeout]); | ||
| + | unistd::close(pipe_in[pipein]); | ||
| + | exit(0); | ||
| + | } | ||
| + | // parent process | ||
| + | if (pid > 0) { | ||
| + | const size_t buffer_size = 1024; | ||
| + | char buffer[buffer_size]; | ||
| + | |||
| + | // close unised ends | ||
| + | unistd::close(pipe_in[pipein]); | ||
| + | unistd::close(pipe_out[pipeout]); | ||
| + | |||
| + | unistd::write(pipe_in[pipeout], msg.c_str(), msg.size()); | ||
| + | unistd::close(pipe_in[pipeout]); | ||
| + | |||
| + | ssize_t count; | ||
| + | while ((count = unistd::read(pipe_out[pipein], &buffer, buffer_size)) > 0) { | ||
| + | result.append(buffer, count); | ||
| + | } | ||
| + | unistd::close(pipe_out[pipein]); | ||
| + | unistd::wait(NULL); | ||
| + | |||
| + | } | ||
| + | return result; | ||
| + | } | ||
| + | |||
| + | int main(int argc, char **argv) { | ||
| + | |||
| + | std::string cmd = "/sbin/md5"; | ||
| + | std::string msg = "hello"; | ||
| + | |||
| + | std::cout << execv3(cmd, msg); | ||
| + | return 0; | ||
| + | } | ||
| + | </code> | ||
| + | |||
| + | ===Out=== | ||
| + | |||
| + | <file> | ||
| + | $ c++ -Wall -O -std=c++11 -o pipe pipe.cpp | ||
| + | |||
| + | $ ./pipe | ||
| + | 5d41402abc4b2a76b9719d911017c592 | ||
| + | |||
| + | $ echo hello | md5 | ||
| + | 5d41402abc4b2a76b9719d911017c592 | ||
| + | |||
| + | </file> | ||
| + | |||
| + | ---- | ||
| + | [<>] | ||