它更像是C或glibc问题.你必须使用fflush(stdout).

为什么？在终端中运行a.out和从PHP调用它有什么区别？

答：如果你在终端中运行a.out(正在使用stdin),那么glibc将使用行缓冲IO.但是如果你从另一个程序运行它(在这种情况下为PHP)并且它的stdin是一个管道(或者其他什么但不是tty),而glibc将使用内部IO缓冲.这就是为什么第一个fgets()如果没有注释就会阻塞.有关更多信息,请查看此article.

好消息：您可以使用stdbuf命令控制此缓冲.将$run_string更改为：

$run_string = "cd ".$addr_base.";stdbuf -o0 ./a.out 2>&1";

这是一个有效的例子.即使C代码不关心fflush(),因为它使用stdbuf命令：

启动子流程

$cmd = 'stdbuf -o0 ./a.out 2>&1';

// what pipes should be used for STDIN, STDOUT and STDERR of the child

$descriptorspec = array (

0 => array("pipe", "r"),

1 => array("pipe", "w"),

2 => array("pipe", "w")

);

// open the child

$proc = proc_open (

$cmd, $descriptorspec, $pipes, getcwd()

);

将所有流设置为非阻塞模式

// set all streams to non blockin mode

stream_set_blocking($pipes[1], 0);

stream_set_blocking($pipes[2], 0);

stream_set_blocking(STDIN, 0);

// check if opening has succeed

if($proc === FALSE){

throw new Exception('Cannot execute child process');

}

得到孩子的pid.我们以后需要它

// get PID via get_status call

$status = proc_get_status($proc);

if($status === FALSE) {

throw new Exception (sprintf(

'Failed to obtain status information '

));

}

$pid = $status['pid'];

轮询直到孩子终止

// now, poll for childs termination

while(true) {

// detect if the child has terminated - the php way

$status = proc_get_status($proc);

// check retval

if($status === FALSE) {

throw new Exception ("Failed to obtain status information for $pid");

}

if($status['running'] === FALSE) {

$exitcode = $status['exitcode'];

$pid = -1;

echo "child exited with code: $exitcode\n";

exit($exitcode);

}

// read from childs stdout and stderr

// avoid *forever* blocking through using a time out (50000usec)

foreach(array(1, 2) as $desc) {

// check stdout for data

$read = array($pipes[$desc]);

$write = NULL;

$except = NULL;

$tv = 0;

$utv = 50000;

$n = stream_select($read, $write, $except, $tv, $utv);

if($n > 0) {

do {

$data = fread($pipes[$desc], 8092);

fwrite(STDOUT, $data);

} while (strlen($data) > 0);

}

}

$read = array(STDIN);

$n = stream_select($read, $write, $except, $tv, $utv);

if($n > 0) {

$input = fread(STDIN, 8092);

// inpput to program

fwrite($pipes[0], $input);

}

}