NAME

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

SYNOPSIS

       #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

       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

       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

           #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

           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

       libtraceevent(3), trace-cmd(1)

AUTHOR

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

REPORTING BUGS

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

LICENSE

       libtraceevent is Free Software licensed under the GNU LGPL 2.1

RESOURCES

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

NOTES

        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