Pipeline issue

[zzzSleep]

Could I ask some questions on the pipeline, the following code 
always stops at the second cmds, cmds[1]. I tested the command 
under shell and found it can quickly end and get output.bam

```
import std.process;
import std.stdio;
import std.conv;
void executeCommandPipe(string[][] cmds) {

     // pipe init
     auto temp_pipe = pipe(); // save cmd1, cmd2, cmd3 ...

     // process first
     auto pid_first = spawnProcess(cmds[0], stdin, 
temp_pipe.writeEnd);
     scope(exit) wait(pid_first);

     // process cmd2 ~ cmdN-1
     for (int i = 1; i < cmds.length - 1; i++) {
         auto new_pipe = pipe(); // create next pipe

         auto pid = spawnProcess(cmds[i], temp_pipe.readEnd, 
new_pipe.writeEnd);
         scope(exit) wait(pid);

         temp_pipe = new_pipe; // update the pipe
     }

     // process final, output to stdout
     auto pid_final = spawnProcess(cmds[$-1], temp_pipe.readEnd, 
stdout);
     scope(exit) wait(pid_final);
}
void main() {
     string[][]cmds=[["samtools", "fixmate", "-@", "8", "-m", 
"-u", "input.bam", "-"], ["samtools", "sort", "-@", "8", "-u", 
"-",], ["samtools", "markdup", "-@", "8", "-u", "-", 
"output.bam"]];
     executeCommandPipe(cmds);
}

```
corresponding Linux command is
```
samtools fixmate -@ 8 -m -u input.bam - | samtools sort -@ 8 -u - 
| samtools markdup -u - output.bam
```