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97 lines
2.1 KiB
97 lines
2.1 KiB
/*
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* Copyright 2002-2019 Intel Corporation.
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*
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* This software is provided to you as Sample Source Code as defined in the accompanying
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* End User License Agreement for the Intel(R) Software Development Products ("Agreement")
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* section 1.L.
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*
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* This software and the related documents are provided as is, with no express or implied
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* warranties, other than those that are expressly stated in the License.
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*/
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#include <sched.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <cstdlib>
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#include <cstdio>
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#include <cstring>
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#include <cerrno>
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/* Stack size for cloned child */
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#define STACK_SIZE (1024 * 1024)
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#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \
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} while (0)
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/* Pipe for connection between main process and child */
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int myPipe[2];
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/* Start function for cloned child */
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static int childFunc(void *arg)
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{
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/* Close unused read side */
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close(myPipe[0]);
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/* Write to the pipe */
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write(myPipe[1], "child wrote!!", strlen("child wrote!!"));
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/* exit() closes the write side */
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exit(EXIT_SUCCESS);
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}
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/* main function */
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int main(int argc, char *argv[])
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{
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char * stack = NULL;
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char * stackTop = NULL;
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char buf = '\0';
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int oldStatus = -1;
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pid_t pid = -1;
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/* Allocate stack for child */
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stack = (char*)malloc(STACK_SIZE);
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if (NULL == stack)
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{
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errExit("malloc");
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}
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stackTop = stack + STACK_SIZE;
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/* Inialize pipe */
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if (-1 == pipe(myPipe))
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{
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errExit("pipe");
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}
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/* Set read side to fail if the write side still empty */
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oldStatus = fcntl(myPipe[0], F_GETFL);
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if (-1 == oldStatus)
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{
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errExit("fcntl");
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}
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fcntl(myPipe[0], F_SETFL, oldStatus|O_NONBLOCK);
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/* Create child */
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pid = clone(childFunc, stackTop, CLONE_VFORK, NULL);
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if (-1 == pid)
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{
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errExit("clone");
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}
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/* Close unused write side */
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close(myPipe[1]);
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/* Try to read from pipe, the child should already wrote to the pipe */
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if (-1 == read(myPipe[0], &buf, 1))
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{
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errExit("nonBlocking read failed!");
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}
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/* Close read side */
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close(myPipe[0]);
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free(stack);
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exit(EXIT_SUCCESS);
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}
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