LIBTRACEEVENT(3)

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