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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_error_last, tracefs_error_all, tracefs_error_clear -
functions to read and clear the tracefs error log.
#include <tracefs.h>
char *tracefs_error_last(struct tracefs_instance *instance);
char *tracefs_error_all(struct tracefs_instance *instance);
int tracefs_error_clear(struct tracefs_instance *instance);
The tracefs_error_last() returns the last error message in the
tracefs error log. Several actions that require proper syntax
written into the tracefs file system may produce error messages
in the error log. This function will show the most recent error
in the error log.
The tracefs_error_all() returns all messages saved in the error
log. Note, this may not be all messages that were ever produced,
as the kernel only keeps a limited amount of messages, and older
ones may be discarded by the kernel.
The tracefs_error_clear() will clear the error log.
Both tracefs_error_last() and tracefs_error_all() will return an
allocated string an error exists in the log, otherwise NULL is
returned. If an error occurs, errno will be set, otherwise if
there is no error messages to display then errno is not touched.
tracefs_error_clear() returns 0 on success or -1 on error.
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <tracefs.h>
int main (int argc, char **argv, char **env)
{
struct tracefs_dynevent *kevent;
char *system = NULL;
char *kprobe;
char *format;
char *addr;
int arg = 1;
int ret;
if (argc < 4) {
printf("usage: %s [system] kprobe addr fmt\n", argv[0]);
exit(-1);
}
if (argc > 5)
system = argv[arg++];
kprobe = argv[arg++];
addr = argv[arg++];
format = argv[arg++];
tracefs_error_clear(NULL);
kevent = tracefs_dynevent_get(TRACEFS_DYNEVENT_KPROBE, system, kprobe);
if (kevent) {
tracefs_dynevent_destroy(kevent, true);
tracefs_dynevent_free(kevent);
}
ret = tracefs_kprobe_raw(system, kprobe, addr, format);
if (ret < 0) {
char *err;
perror("Failed creating kprobe");
errno = 0;
err = tracefs_error_last(NULL);
if (err)
fprintf(stderr, "%s\n", err);
else if (errno)
perror("Failed reading error log");
free(err);
}
exit(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)
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 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)
Pages that refer to this page: tracefs_dynevent_create(3), tracefs_kprobe_alloc(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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