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tracefs_trace_pipe_stream(3) — Linux manual page

LIBTRACEFS(3)               libtracefs ManualLIBTRACEFS(3)

NAME        top

       tracefs_trace_pipe_stream, tracefs_trace_pipe_print,       tracefs_trace_pipe_stop - redirect the stream of trace data to an       output or stdout.

SYNOPSIS        top

#include <tracefs.h>       ssize_ttracefs_trace_pipe_stream(intfd, struct tracefs_instance *instance, intflags);       ssize_ttracefs_trace_pipe_print(struct tracefs_instance *instance, intflags);       voidtracefs_trace_pipe_stop(struct tracefs_instance *instance);

DESCRIPTION        top

       If NULL is passed asinstance, the top trace instance is used.       The reading of the trace_pipe file can be stopped by callingtracefs_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.       Thetracefs_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. Thefd is the file descriptor of the output       file andflags is a bit mask of flags to be passed to the open       system call of the trace_pipe file (seeopen(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 theflags and only O_NONBLOCK is useful for this       parameter.       Thetracefs_trace_pipe_print()function is similar totracefs_trace_pipe_stream(), but the stream of trace data is       redirected to stdout.

RETURN VALUE        top

       Thetracefs_trace_pipe_stream(), andtracefs_trace_pipe_print()       functions return the number of bytes transfered if the operation       is successful, or -1 in case of an error.

EXAMPLE        top

           #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;           }

FILES        top

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.

SEE ALSO        top

libtracefs(3),libtraceevent(3),trace-cmd(1),       Documentation/trace/ftrace.rst from the Linux kernel tree

AUTHOR        top

Steven Rostedt<rostedt@goodmis.org[1]>Tzvetomir Stoyanov<tz.stoyanov@gmail.com[2]>

REPORTING BUGS        top

       Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE        top

       libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES        top

https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING        top

       Copyright (C) 2021 VMware, Inc. Free use of this software is       granted under the terms of the GNU Public License (GPL).

NOTES        top

        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

COLOPHON        top

       This page is part of thelibtracefs (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       2025-08-11.  (At that time, the date of the most recent commit       that was found in the repository was 2025-06-02.)  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 isnot part of the original manual page), send a       mail to man-pages@man7.orglibtracefs 1.7.0                12/22/2023LIBTRACEFS(3)

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