linux - 在C中使用Popen调用tshark没有接收到输出

Question

在C中使用popen调用tshark，没有返回输出

例子代码如下：

//开启tshark
FILE *fp = popen("tshark -r t_fifo -T pdml", "r");

//读取popen输出
fread(buffer, 1024, 1, fp);

说明：

1. t_fifo 为创建的FIFO，写入标准PCAP格式报文，用于tshark解析

Answer 1

1 man popen
可以看到
The return value from popen() is a normal standard I/O stream in all respects save that it must be closed with pclose() rather than fclose(3). Writing to

   such a stream writes to the standard input of the command; the command's standard output is the same as that of the process that called popen(), unless this
   is  altered by the command itself.  Conversely, reading from a "popened" stream reads the command's standard output, and the command's standard input is the
   same as that of the process that called popen().

也就是说，其返回值是新进程的STDOUT ； 如果新的进程没有在STDOUT 给出打印，你当然都不到；

2 在linutmint17 中执行
tshark -r t_fifo -T pdml
echo $?
为2；
说明命令不对，并且错误信息被重定向到STDERR了；

如果你向在STDOUT 中获得错误信息，可以使用
tshark -r t_fifo -T pdml 2>&1