| libtracefs(3) |
| ============= |
| |
| NAME |
| ---- |
| tracefs_error_last, tracefs_error_all, tracefs_error_clear - |
| functions to read and clear the tracefs error log. |
| |
| SYNOPSIS |
| -------- |
| [verse] |
| -- |
| *#include <tracefs.h>* |
| |
| char pass:[*]*tracefs_error_last*(struct tracefs_instance pass:[*]_instance_); |
| char pass:[*]*tracefs_error_all*(struct tracefs_instance pass:[*]_instance_); |
| int *tracefs_error_clear*(struct tracefs_instance pass:[*]_instance_); |
| -- |
| |
| DESCRIPTION |
| ----------- |
| 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. |
| |
| RETURN VALUE |
| ------------ |
| 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. |
| |
| EXAMPLE |
| ------- |
| [source,c] |
| -- |
| #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); |
| } |
| -- |
| FILES |
| ----- |
| [verse] |
| -- |
| *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 |
| -------- |
| *libtracefs*(3), |
| *libtraceevent*(3), |
| *trace-cmd*(1) |
| |
| AUTHOR |
| ------ |
| [verse] |
| -- |
| *Steven Rostedt* <rostedt@goodmis.org> |
| *Tzvetomir Stoyanov* <tz.stoyanov@gmail.com> |
| -- |
| REPORTING BUGS |
| -------------- |
| Report bugs to <linux-trace-devel@vger.kernel.org> |
| |
| LICENSE |
| ------- |
| libtracefs is Free Software licensed under the GNU LGPL 2.1 |
| |
| RESOURCES |
| --------- |
| https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ |
| |
| COPYING |
| ------- |
| Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under |
| the terms of the GNU Public License (GPL). |
