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1. 前言
在windows下一般会使用系统的cmd命令或者其他现成的一些命令行可执行程序来完成一些操作，比如：调用ping命令来测试网络是否畅通、调用ffmpeg命令进行视频转码等等。为了能在软件界面上有更好的交互输出，都需要将命令执行的过程拿到，进行处理，然后在界面上进行显示，让用户知道程序正在正常运行，下面就介绍几种输出的获取方式。
当前开发环境: win10 64位 IDE-MSVC2017
2. 使用_popen执行进程
通过_popen打开进程进行执行，通过fgets获取进程的输出。
#include <stdio.h>
#include <string.h>
int run_cmd(const char * cmd)
{
char MsgBuff[1024];
int MsgLen=1020;
FILE * fp;
if (cmd == NULL)
{
return -1;
}
if ((fp = _popen(cmd, "r")) == NULL)
{
return -2;
}
else
{
memset(MsgBuff, 0, MsgLen);
//读取命令执行过程中的输出
while (fgets(MsgBuff, MsgLen, fp) != NULL)
{
printf("MsgBuff: %s\n", MsgBuff);
}
//关闭执行的进程
if(_pclose(fp) == -1)
{
return -3;
}
}
return 0;
}
int main()
{
//const char *cmd = "ffmpeg -i D:\123.mp4 -vf reverse D:\out\out1.mp4";
const char *cmd = "ping www.baidu.com";
int ret = 0;
ret = run_cmd(cmd);
printf("命令执行结果:%d\r\n",ret);
getchar();
return 0;
}
3. CreateProcess重定向输出到文件
下面使用CreateProcess调用子进程运行，将输出保存在文件中，阻塞等待进程执行完毕。
int my_CreateProcess()
{
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
_unlink("D:/out/output.log");
HANDLE h = CreateFile((L"D:/out/output.log"),
FILE_APPEND_DATA,
FILE_SHARE_WRITE | FILE_SHARE_READ,
&sa,
OPEN_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
NULL);
PROCESS_INFORMATION pi;
STARTUPINFO si;
BOOL ret = FALSE;
DWORD flags = CREATE_NO_WINDOW;
ZeroMemory(&pi, sizeof(PROCESS_INFORMATION));
ZeroMemory(&si, sizeof(STARTUPINFO));
si.cb = sizeof(STARTUPINFO);
si.dwFlags |= STARTF_USESTDHANDLES;
si.hStdInput = NULL;
si.hStdError = h;
si.hStdOutput = h;
TCHAR cmd[] = TEXT("ping www.baidu.com");
ret = CreateProcess(NULL, cmd, NULL, NULL, TRUE, flags, NULL, NULL, &si, &pi);
if (ret)
{
WaitForSingleObject(pi.hProcess, INFINITE);
printf("执行成功....\n");
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
//关闭文件
CloseHandle(h);
return 0;
}
//关闭文件
CloseHandle(h);
printf("执行失败....\n");
return -1;
}
4. CreateProcess重定向输出到管道
为了能实时获取CreateProcess打开进程运行时实时输出的结果，可以将CreateProcess的输出重定向到管道文件，CreateProcess将数据写到管道的写端，在父进程里再从管道的读端就能实时读取数据。
int my_CreateProcess()
{
BOOL run_pipe;
PROCESS_INFORMATION pi;
STARTUPINFO si;
BOOL ret = FALSE;
DWORD flags = CREATE_NO_WINDOW;
_unlink("D:/out/output.log");
char pBuffer[210];
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
HANDLE hReadPipe, hWritePipe;
run_pipe=CreatePipe(&hReadPipe, &hWritePipe, &sa, 0);
printf("run_pipe=%d\n", run_pipe);
ZeroMemory(&pi, sizeof(PROCESS_INFORMATION));
ZeroMemory(&si, sizeof(STARTUPINFO));
si.cb = sizeof(STARTUPINFO);
si.dwFlags |= STARTF_USESTDHANDLES;
si.hStdInput = NULL;
si.hStdError = hWritePipe;
si.hStdOutput = hWritePipe;
TCHAR cmd[] = TEXT("ffmpeg -i D:\123.mp4 -vf reverse D:\out\out1.mp4");
ret = CreateProcess(NULL, cmd, NULL, NULL, TRUE, flags, NULL, NULL, &si, &pi);
if (ret)
{
while (true)
{
DWORD ExitCode = 0;
//判断进程是否执行结束
GetExitCodeProcess(pi.hProcess, &ExitCode);
if (ExitCode == STILL_ACTIVE) //正在运行
{
DWORD RSize=0;
BOOL run_s=0;
run_s =ReadFile(hReadPipe, pBuffer,200,&RSize,NULL);
pBuffer[RSize] = '\0';
printf("返回结果:%d,%d,%s\n", run_s, RSize, pBuffer);
}
else //结束
{
printf("执行完毕...\n");
break;
}
}
//WaitForSingleObject(pi.hProcess, INFINITE);
printf("执行成功....\n");
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
return 0;
}
printf("执行失败....\n");
return -1;
}
