在
Linux 3.0 / C下：
我想要一个功能,执行以下操作：
string f(string s)
{
string r = system("foo < s");
return r;
}
显然上述不行,但你得到这个想法.我有一个字符串,我想通过作为应用程序“foo”的子进程执行的标准输入,然后我想将其标准输出记录到字符串r,然后返回.
解决方法
eerpini提供的代码无法正常工作.注意,例如,之后使用在父项中关闭的管道结束.看着
close(wpipefd[1]);
并且随后写入关闭的描述符.这只是转置,但是它显示这个代码从未被使用过.以下是我测试过的一个版本.不幸的是,我改变了代码风格,所以这不被接受为编辑eerpini的代码.
唯一的结构性变化是我只重定向孩子中的I / O(请注意,dup2调用仅在子路径中)这是非常重要的,因为否则父进程的I / O会被弄乱.感谢eerpini的初步答案,我用来开发这个答案.
#define PIPE_READ 0
#define PIPE_WRITE 1
int createChild(const char* szCommand,char* const aArguments[],char* const aEnvironment[],const char* szMessage) {
int aStdinPipe[2];
int aStdoutPipe[2];
int nChild;
char nChar;
int nResult;
if (pipe(aStdinPipe) < 0) {
perror("allocating pipe for child input redirect");
return -1;
}
if (pipe(aStdoutPipe) < 0) {
close(aStdinPipe[PIPE_READ]);
close(aStdinPipe[PIPE_WRITE]);
perror("allocating pipe for child output redirect");
return -1;
}
nChild = fork();
if (0 == nChild) {
// child continues here
// redirect stdin
if (dup2(aStdinPipe[PIPE_READ],STDIN_FILENO) == -1) {
perror("redirecting stdin");
return -1;
}
// redirect stdout
if (dup2(aStdoutPipe[PIPE_WRITE],STDOUT_FILENO) == -1) {
perror("redirecting stdout");
return -1;
}
// redirect stderr
if (dup2(aStdoutPipe[PIPE_WRITE],STDERR_FILENO) == -1) {
perror("redirecting stderr");
return -1;
}
// all these are for use by parent only
close(aStdinPipe[PIPE_READ]);
close(aStdinPipe[PIPE_WRITE]);
close(aStdoutPipe[PIPE_READ]);
close(aStdoutPipe[PIPE_WRITE]);
// run child process image
// replace this with any exec* function find easier to use ("man exec")
nResult = execve(szCommand,aArguments,aEnvironment);
// if we get here at all,an error occurred,but we are in the child
// process,so just exit
perror("exec of the child process");
exit(nResult);
} else if (nChild > 0) {
// parent continues here
// close unused file descriptors,these are for child only
close(aStdinPipe[PIPE_READ]);
close(aStdoutPipe[PIPE_WRITE]);
// Include error check here
if (NULL != szMessage) {
write(aStdinPipe[PIPE_WRITE],szMessage,strlen(szMessage));
}
// Just a char by char read here,you can change it accordingly
while (read(aStdoutPipe[PIPE_READ],&nChar,1) == 1) {
write(STDOUT_FILENO,1);
}
// done with these in this example program,you would normally keep these
// open of course as long as you want to talk to the child
close(aStdinPipe[PIPE_WRITE]);
close(aStdoutPipe[PIPE_READ]);
} else {
// Failed to create child
close(aStdinPipe[PIPE_READ]);
close(aStdinPipe[PIPE_WRITE]);
close(aStdoutPipe[PIPE_READ]);
close(aStdoutPipe[PIPE_WRITE]);
}
return nChild;
}
