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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
tracefs_trace_pipe_stream, tracefs_trace_pipe_print,
tracefs_trace_pipe_stop - redirect the stream of trace data to an
output or stdout.
#include <tracefs.h>
ssize_t tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags);
ssize_t tracefs_trace_pipe_print(struct tracefs_instance *instance, int flags);
void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
If NULL is passed as instance, the top trace instance is used.
The reading of the trace_pipe file can be stopped by calling
tracefs_trace_pipe_stop() which could be placed in a signal
handler in case the application wants to stop the reading, for
example, with the user pressing Ctrl-C.
The tracefs_trace_pipe_stream() function redirects the stream of
trace data to an output file. The "splice" system call is used to
moves the data without copying between kernel address space and
user address space. The fd is the file descriptor of the output
file and flags is a bit mask of flags to be passed to the open
system call of the trace_pipe file (see open(2)). If flags
contain O_NONBLOCK, then that is also passed to the splice calls
that may read the file to the output stream file descriptor.
Note, O_RDONLY is or’d to the flags and only O_NONBLOCK is useful
for this parameter.
The tracefs_trace_pipe_print() function is similar to
tracefs_trace_pipe_stream(), but the stream of trace data is
redirected to stdout.
The tracefs_trace_pipe_stream(), and tracefs_trace_pipe_print()
functions return the number of bytes transfered if the operation
is successful, or -1 in case of an error.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <tracefs.h>
void stop(int sig)
{
tracefs_trace_pipe_stop(NULL);
}
int main(int argc, char **argv)
{
mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
const char *filename;
int fd;
int ret;
if (argc < 2) {
fprintf(stderr, "usage: %s output_file\n", argv[0]);
exit(-1);
}
filename = argv[1];
fd = creat(filename, mode);
if (fd < 0) {
perror(filename);
exit(-1);
}
signal(SIGINT, stop);
ret = tracefs_trace_pipe_stream(fd, NULL, SPLICE_F_NONBLOCK);
close(fd);
return ret;
}
tracefs.h
Header file to include in order to have access to the library APIs.
-ltracefs
Linker switch to add when building a program that uses the library.
libtracefs(3), libtraceevent(3), trace-cmd(1),
Documentation/trace/ftrace.rst from the Linux kernel tree
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2021 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This
page was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2023-12-22. (At that time, the date of the most recent commit
that was found in the repository was 2023-07-05.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
libtracefs 1.7.0 12/22/2023 LIBTRACEFS(3)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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