tep_get_any_field_val(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | NOTES | COLOPHON

LIBTRACEEVENT(3)          libtraceevent Manual          LIBTRACEEVENT(3)

NAME         top

       tep_get_any_field_val, tep_get_common_field_val,
       tep_get_field_val, tep_get_field_raw - Get value of a field.

SYNOPSIS         top

       #include <event-parse.h>
       #include <trace-seq.h>

       int tep_get_any_field_val(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, unsigned long long *val, int err);
       int tep_get_common_field_val(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, unsigned long long *val, int err);
       int tep_get_field_val(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, unsigned long long *val, int err);
       void *tep_get_field_raw(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, int *len, int err);

DESCRIPTION         top

       These functions can be used to find a field and retrieve its
       value.

       The tep_get_any_field_val() function searches in the record for a
       field with name, part of the event. If the field is found, its
       value is stored in val. If there is an error and err is not zero,
       then an error string is written into s.

       The tep_get_common_field_val() function does the same as
       tep_get_any_field_val(), but searches only in the common fields.
       This works for any event as all events include the common fields.

       The tep_get_field_val() function does the same as
       tep_get_any_field_val(), but searches only in the event specific
       fields.

       The tep_get_field_raw() function searches in the record for a
       field with name, part of the event. If the field is found, a
       pointer to where the field exists in the record’s raw data is
       returned. The size of the data is stored in len. If there is an
       error and err is not zero, then an error string is written into
       s.

RETURN VALUE         top

       The tep_get_any_field_val(), tep_get_common_field_val() and
       tep_get_field_val() functions return 0 on success, or -1 in case
       of an error.

       The tep_get_field_raw() function returns a pointer to field’s raw
       data, and places the length of this data in len. In case of an
       error NULL is returned.

EXAMPLE         top

           #include <event-parse.h>
           #include <trace-seq.h>
           ...
           struct tep_handle *tep = tep_alloc();
           ...
           struct tep_event *event = tep_find_event_by_name(tep, "kvm", "kvm_exit");
           ...
           void process_record(struct tep_record *record)
           {
                   int len;
                   char *comm;
                   struct tep_event *event;
                   unsigned long long val;

                   event = tep_find_event_by_record(tep, record);
                   if (event != NULL) {
                           if (tep_get_common_field_val(NULL, event, "common_type",
                                                        record, &val, 0) == 0) {
                                   /* Got the value of common type field */
                           }
                           if (tep_get_field_val(NULL, event, "pid", record, &val, 0) == 0) {
                                   /* Got the value of pid specific field */
                           }
                           comm = tep_get_field_raw(NULL, event, "comm", record, &len, 0);
                           if (comm != NULL) {
                                   /* Got a pointer to the comm event specific field */
                           }
                   }
           }

FILES         top

           event-parse.h
                   Header file to include in order to have access to the library APIs.
           trace-seq.h
                   Header file to include in order to have access to trace sequences
                   related APIs. Trace sequences are used to allow a function to call
                   several other functions to create a string of data to use.
           -ltraceevent
                   Linker switch to add when building a program that uses the library.

SEE ALSO         top

       libtraceevent(3), trace-cmd(1)

AUTHOR         top

           Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.

REPORTING BUGS         top

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

LICENSE         top

       libtraceevent is Free Software licensed under the GNU LGPL 2.1

RESOURCES         top

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

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 the libtraceevent (Linux kernel trace event
       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/libtraceevent.git⟩
       on 2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-05-17.)  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

libtraceevent 1.7.3            09/24/2023               LIBTRACEEVENT(3)