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

2.

tz.stoyanov@gmail.com

3.

linux-trace-devel@vger.kernel.org