annotate pipes.cpp @ 0:21b543c7aa14

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author Yasuri <yasuri@charliesmp.net>
date Sun, 13 Sep 2026 19:19:56 +0000
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children 00b62a080354
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1 #include <iostream>
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2 #include <unistd.h>
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3 #include <spawn.h>
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4 #include <cstring>
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5 #include <string>
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6 #include <sys/wait.h>
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7 #include "process.h"
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8 extern char** environ;
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9 std::string run_piped(const char* path, char* const argv[], const std::string& input)
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10 {
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11 int status;
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12 pid_t pid;
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13 int pipeA[2];
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14 int pipeB[2];
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15 if (pipe(pipeA) < 0)
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16 return "error";
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17 if (pipe(pipeB) < 0)
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18 return "error";
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19 posix_spawn_file_actions_t actions;
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20 posix_spawn_file_actions_init(&actions); // initialize actions
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21 posix_spawn_file_actions_adddup2(&actions, pipeA[0], STDIN_FILENO);
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22 posix_spawn_file_actions_adddup2(&actions, pipeB[1], STDOUT_FILENO);
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23 posix_spawn_file_actions_addclose(&actions, pipeA[1]); // closes write end in child
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24 posix_spawn_file_actions_addclose(&actions, pipeB[0]); // makes sure child doesn't read its own output pipe
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25 posix_spawn_file_actions_addclose(&actions, pipeA[0]); // close read fd in child
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26 posix_spawn_file_actions_addclose(&actions, pipeB[1]); // close read fd in child, part 2
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27 status = posix_spawn(&pid, path, &actions, NULL, const_cast<char* const*>(argv), environ);
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28 close(pipeA[0]);
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29 close(pipeB[1]);
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30 if (status != 0) {
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31 posix_spawn_file_actions_destroy(&actions);
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32 close(pipeA[1]);
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33 close(pipeB[0]);
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34 std::cerr << "posix_spawn failed: " << strerror(status) << std::endl;
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35 return "error";
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36 }
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37 write(pipeA[1],input.c_str(), input.size());
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38 close(pipeA[1]);
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39 char buf[256];
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40 std::string result;
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41 ssize_t n;
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42 while ((n = read(pipeB[0], buf, sizeof(buf))) > 0) {
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43 result.append(buf, n);
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44 }
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45 close(pipeB[0]);
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46 if (waitpid(pid, &status, 0) == -1) {
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47 posix_spawn_file_actions_destroy(&actions);
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48 close(pipeA[1]);
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49 close(pipeB[0]);
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50 perror("waitpid");
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51 return "error";
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52 }
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53 posix_spawn_file_actions_destroy(&actions);
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54 return result;
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55 }