大多数的IDE环境都具备这样一种功能，加载编译器编译好程序并执行，执行结果显示于IDE环境中的结果信息窗口，那么它是如何捕获程序运行结果的呢？其实简单地用dup/dup2重定位输出并通过管道获取该输出就可以达到这种效果。#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
int
main(int argc, char **argv)
{
int fd[2];
pid_t childpid;
if (pipe(fd) == -1)
{
printf("%s: %d -- Create pipe error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
childpid = fork();
if (childpid == -1)
{
printf("%s: %d -- fork error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
if (childpid == 0)
{
close(fd[0]);
if (dup2(fd[1], STDOUT_FILENO) == -1)
{
printf("%s: %d -- dup2 error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
if (execlp("ls", "ls", "/", NULL) == -1)
{
printf("%s: %d -- execlp error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
exit(0);
}
else
{
char buff[4096];
close(fd[1]);
memset(buff, sizeof(buff), 0);
printf("read %d bytes\n", read(fd[0], buff, sizeof(buff)));
printf("output: %s\n", buff);
exit(0);
}
}
以下代码则相反，重定向输入：
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
int
main(int argc, char **argv)
{
int fd[2];
pid_t childpid;
if (pipe(fd) == -1)
{
printf("%s: %d -- Create pipe error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
childpid = fork();
if (childpid == -1)
{
printf("%s: %d -- fork error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
if (childpid == 0)
{
close(fd[1]);
if (dup2(fd[0], STDIN_FILENO) == -1)
{
printf("%s: %d -- dup2 error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
if (execlp("xargs", "xargs", "ls", NULL) == -1)
{
printf("%s: %d -- execlp error: %s\n", __FILE__, __LINE__, strerror(errno));
exit(errno);
}
exit(0);
}
else
{
int status;
close(fd[0]);
write(fd[1], "/", 1);
printf("waitpid result: %d\n", waitpid(childpid, &status, WNOHANG));
printf("status value: %d\n", status);
if (WIFEXITED(status))
printf("child process was terminated normally by calling exit or _exit\n");
else if (WEXITSTATUS(status))
printf("returns the exit status of the child by exit or _exit\n");
else if (WIFSIGNALED(status))
printf("child process was terminated by a signal\n");
else if (WTERMSIG(status))
printf("returns the number of the signal that caused the child process to terminate\n");
else if (WCOREDUMP(status))
printf("child produced a core dump\n");
else if (WIFSTOPPED(status))
printf("child process was stopped by delivery of a signal\n");
else if (WSTOPSIG(status))
printf("retuns the number of the signal which caused the child to stop\n");
else if (WIFCONTINUED(status))
printf("child process was resumed by delivery of SIGCONT\n");
exit(0);
}
}
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