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### 13.4 Using Trace Files

In some situations, the target running a trace experiment may no longer be available; perhaps it crashed, or the hardware was needed for a different activity. To handle these cases, you can arrange to dump the trace data into a file, and later use that file as a source of trace data, via the `target tfile` command.

`tsave [ -r ]` filename
`tsave [-ctf]` dirname
  Save the trace data to filename. By default, this command assumes that filename refers to the host filesystem, so if necessary gdb will copy raw trace data up from the target and then save it. If the target supports it, you can also supply the optional argument `-r` (“remote”) to direct the target to save the data directly into filename in its own filesystem, which may be more efficient if the trace buffer is very large. (Note, however, that `target tfile` can only read from files accessible to the host.) By default, this command will save trace frame in tfile format. You can supply the optional argument `-ctf` to save date in CTF format. The Common Trace Format (CTF) is proposed as a trace format that can be shared by multiple debugging and tracing tools. Please go to <`http://www.efficios.com/ctf`> to get more information.

`target tfile` filename
`target ctf` dirname
  Use the file named filename or directory named dirname as a source of trace data. Commands that examine data work as they do with a live target, but it is not possible to run any new trace experiments. `tstatus` will report the state of the trace run at the moment the data was saved, as well as the current trace frame you are examining. Both filename and dirname must be on a filesystem accessible to the host.

                (gdb) target ctf ctf.ctf
                (gdb) tfind
                Found trace frame 0, tracepoint 2
                39            ++a;  /* set tracepoint 1 here */
                (gdb) tdump
                Data collected at tracepoint 2, trace frame 0:
                i = 0
                a = 0
                b = 1 '\001'
                c = {"123", "456", "789", "123", "456", "789"}
                d = {{{a = 1, b = 2}, {a = 3, b = 4}}, {{a = 5, b = 6}, {a = 7, b = 8}}}
                (gdb) p b
                $1 = 1