From ftrace documentation:

trace_pipe: The output is the same as the "trace" file but this file is meant to be streamed with live tracing. Reads from this file will block until new data is retrieved. Unlike the "trace" file, this file is a consumer. This means reading from this file causes sequential reads to display more current data. Once data is read from this file, it is consumed, and will not be read again with a sequential read. The "trace" file is static, and if the tracer is not adding more data, it will display the same information every time it is read. This file will not disable tracing while being read 

Or use trace-cmd(1), and specifically trace-cmd-show. From it's man:

-p Instead of displaying the contents of the "trace" file, use the "trace_pipe" file. The difference between the two is that the "trace" file is static. That is, if tracing is stopped, the "trace" file will show the same contents each time. The "trace_pipe" file is a consuming read, where a read of the file will consume the output of what was read and it will not read the same thing a second time even if tracing is stopped. This file als will block. If no data is available, trace-cmd show will stop and wait for data to appear. 

Also see this answer to see how you can change the size and behavior of the trace` file.

From ftrace documentation:

trace_pipe:

The output is the same as the "trace" file but this file is meant to be streamed with live tracing.  Reads from this file will block until new data is retrieved.  Unlike the "trace" file, this file is a consumer.  This means reading from this file causes sequential reads to display more current data.  Once data is read from this file, it is consumed, and will not be read again with a sequential read.  The "trace" file is static, and if the tracer is not adding more data, it will display the same information every time it is read.  This file will not disable tracing while being read.

Or use trace-cmd(1), and specifically trace-cmd-show.  From its man page:

-p                        (lower case 'P')

Instead of displaying the contents of the "trace" file, use the "trace_pipe" file. The difference between the two is that the "trace" file is static. That is, if tracing is stopped, the "trace" file will show the same contents each time.

The "trace_pipe" file is a consuming read, where a read of the file will consume the output of what was read and it will not read the same thing a second time even if tracing is stopped. This file als will block.  If no data is available, trace-cmd show will stop and wait for data to appear.

Also see Knio's answer to How to set the buffer size for trace_pipe in ftrace? (on Stack Overflow) to see how you can change the size and behavior of the trace file.

From ftrace documentation:

trace_pipe: The output is the same as the "trace" file but this file is meant to be streamed with live tracing. Reads from this file will block until new data is retrieved. Unlike the "trace" file, this file is a consumer. This means reading from this file causes sequential reads to display more current data. Once data is read from this file, it is consumed, and will not be read again with a sequential read. The "trace" file is static, and if the tracer is not adding more data, it will display the same information every time it is read. This file will not disable tracing while being read 

Or use trace-cmd(1), and specifically trace-cmd-show. From it's man:

-p Instead of displaying the contents of the "trace" file, use the "trace_pipe" file. The difference between the two is that the "trace" file is static. That is, if tracing is stopped, the "trace" file will show the same contents each time. The "trace_pipe" file is a consuming read, where a read of the file will consume the output of what was read and it will not read the same thing a second time even if tracing is stopped. This file als will block. If no data is available, trace-cmd show will stop and wait for data to appear. 

From ftrace documentation:

trace_pipe: The output is the same as the "trace" file but this file is meant to be streamed with live tracing. Reads from this file will block until new data is retrieved. Unlike the "trace" file, this file is a consumer. This means reading from this file causes sequential reads to display more current data. Once data is read from this file, it is consumed, and will not be read again with a sequential read. The "trace" file is static, and if the tracer is not adding more data, it will display the same information every time it is read. This file will not disable tracing while being read 

Or use trace-cmd(1), and specifically trace-cmd-show. From it's man:

-p Instead of displaying the contents of the "trace" file, use the "trace_pipe" file. The difference between the two is that the "trace" file is static. That is, if tracing is stopped, the "trace" file will show the same contents each time. The "trace_pipe" file is a consuming read, where a read of the file will consume the output of what was read and it will not read the same thing a second time even if tracing is stopped. This file als will block. If no data is available, trace-cmd show will stop and wait for data to appear. 

Also see this answer to see how you can change the size and behavior of the trace` file.