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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |EXAMPLE |FILES |SEE ALSO |AUTHOR |REPORTING BUGS |LICENSE |RESOURCES |COPYING |NOTES |COLOPHON | |
LIBTRACEFS(3) libtracefs ManualLIBTRACEFS(3)tracefs_file_exists, tracefs_dir_exists, tracefs_instance_get_file, tracefs_instance_get_dir - Work with files directories in tracing instances.
#include <tracefs.h> booltracefs_file_exists(struct tracefs_instance *instance, char *name); booltracefs_dir_exists(struct tracefs_instance *instance, char *name); char *tracefs_instance_get_file(struct tracefs_instance *instance, const char *file); char *tracefs_instance_get_dir(struct tracefs_instance *instance);
This set of APIs can be used to work with trace files in all trace instances. Each of these APIs take aninstance argument, that can be NULL to act on the top level instance. Otherwise, it acts on an instance created withtracefs_insance_create(3) Thetracefs_file_exists()function checks if a file withname exists ininstance. Thetracefs_dir_exists()function checks if a directory withname exists ininstance. Thetracefs_instance_get_file()function returns the full path of the file with givenname ininstance. Note, it does not check if the file exists in the instance. Thetracefs_instance_get_dir()function returns the full path of the directory with givenname ininstance. Note, it does not check if the directory exists in the instance.
Thetracefs_file_exists()andtracefs_dir_exists()functions return true if the file / directory exist in the given instance or false if it does not exist. Thetracefs_instance_get_file()andtracefs_instance_get_dir() functions return a string or NULL in case of an error. The returned string must be freed withtracefs_put_tracing_file().
#include <tracefs.h> struct tracefs_instance *inst = tracefs_instance_create("foo"); if (!inst) { /* Error creating a new trace instance */ ... } if (tracefs_file_exists(inst,"trace_clock")) { /* The instance foo supports trace clock */ char *path, *clock; int size; path = = tracefs_instance_get_file(inst, "trace_clock") if (!path) { /* Error getting the path to trace_clock file in instance foo */ ... } ... tracefs_put_tracing_file(path); clock = tracefs_instance_file_read(inst, "trace_clock", &size); if (!clock) { /* Failed to read trace_clock file in instance foo */ ... } ... free(clock); if (tracefs_instance_file_write(inst, "trace_clock", "global") != strlen("global")) { /* Failed to set gloabl trace clock in instance foo */ ... } } else { /* The instance foo does not support trace clock */ } if (tracefs_dir_exists(inst,"options")) { /* The instance foo supports trace options */ char *path = tracefs_instance_get_file(inst, "options"); if (!path) { /* Error getting the path to options directory in instance foo */ ... } tracefs_put_tracing_file(path); } else { /* The instance foo does not support trace options */ } ... if (tracefs_instance_is_new(inst)) tracefs_instance_destroy(inst); else tracefs_instance_free(inst); ... long long int res; if (tracefs_instance_file_read_number(NULL, "tracing_on", &res) == 0) { if (res == 0) { /* tracing is disabled in the top instance */ } else if (res == 1) { /* tracing is enabled in the top instance */ } else { /* Unknown tracing state of the top instance */ } } else { /* Failed to read integer from tracing_on file */ } ... int fd; fd = tracefs_instance_file_open(NULL, "tracing_on", O_WRONLY); if (fd >= 0) { /* Got file descriptor to the tracing_on file from the top instance for writing */ ... close(fd); }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)
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) 2020 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 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)Pages that refer to this page:kbuffer_alloc(3), tracefs_event_get_file(3)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |