1

我想将系统调用的 std 输出读入 C/C++ 字符串。我可以在不使用临时文件的情况下执行此操作吗?

Perl

//without file io
$output = `echo hello`;

C++

//with file io
system ("echo hello > tmp");
std::fstream file ("tmp");
std::string s;
file >> s;
4

2 回答 2

2

使用 C popen(可能是最简单的解决方案,即使它不使用 C++ iostream):

FILE *p = popen("echo hello", "r");
std::string s;
for (size_t count; (count = fread(buf, 1, sizeof(buf), p));)
    s += string(buf, buf + count);
pclose(p);

假设您iostream有非标准的x fstream::xfstream(int fd)构造函数:

FILE *p = popen("echo hello", "r");
std::ifstream p2(fileno(p));
std::string s;
p2 >> s;
p2.close();
pclose(p);

使用Boost.Iostreams,您不必依赖以下非标准扩展iostream

boost::iostreams::file_descriptor_source p2(fileno(p));

不幸的是,Windows 很糟糕,_popen只适用于控制台应用程序;对于图形应用程序:

SECURITY_ATTRIBUTES sec;
sec.nLength = sizeof(sec);
sec.bInheritHandle = TRUE;
sec.lpSecurityDescriptor = NULL;
HANDLE *h[2];
CreatePipe(&h[0], &h[1], &sec, 0);
SetHandleInformation(h[0], HANDLE_FLAG_INHERIT, 0)
STARTUPINFO si;
memset((void *)&si, 0, sizeof(si));
si.hStdInput = INVALID_HANDLE_VALUE;
si.hStdOutput = h[1];
si.hStdError = INVALUD_HANDLE_VALUE;
si.dwFlags |= STARTF_USESTDHANDLES;
CreateProcess(NULL, "cmd /c \"echo hello\"", NULL, NULL, TRUE, 0, NULL, NULL, &si, NULL);
boost::iostreams::file_descriptor_source p(h[0]);

(完全未经测试)

于 2009-07-09T16:29:35.997 回答
0

可能会帮助您从系统调用重定向标准输出。

于 2009-07-09T11:42:52.563 回答