tep_print_field_content - Man Page

Print the field content.

Synopsis

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

void tep_print_field_content(struct trace_seq *s, void *data, int size, struct tep_format_field *field);
void tep_print_fields(struct trace_seq *s, void *data, int size, struct tep_event *event);
int tep_print_num_field(struct trace_seq *s, const char *fmt, struct tep_event *event, const char *name, struct tep_record *record, int err);
int tep_print_func_field(struct trace_seq *s, const char *fmt, struct tep_event *event, const char *name, struct tep_record *record, int err);
void tep_record_print_fields(struct trace_seq *s, struct tep_record *record, struct tep_event *event);
void tep_record_print_selected_fields(struct trace_seq *s, struct tep_record *record, struct tep_event *event, int select_mask);

Description

These functions print recorded field’s data, according to the field’s type.

The tep_print_field_content() function extracts from the recorded raw data value of the field and prints it into s, according to the field type.

The tep_print_fields() prints each field name followed by the record’s field value according to the field’s type:

"field1_name=field1_value field2_name=field2_value ..."

It iterates all fields of the event, and calls tep_print_field_content() for each of them.

The tep_print_num_field() function prints a numeric field with given format string. A search is performed in the event for a field with name. If such field is found, its value is extracted from the record and is printed in the s, according to the given format string fmt. If the argument err is non-zero, and an error occures - it is printed in the s.

The tep_print_func_field() function prints a function field with given format string. A search is performed in the event for a field with name. If such field is found, its value is extracted from the record. The value is assumed to be a function address, and a search is perform to find the name of this function. The function name (if found) and its address are printed in the s, according to the given format string fmt. If the argument err is non-zero, and an error occures - it is printed in s.

The tep_record_print_fields() prints the field’s name followed by its value for all record’s field.

The tep_record_print_selected_fields() prints the field’s name followed by its value for selected subset of record field. The fields to be printed are defined by the select_mask bit mask.

Return Value

The tep_print_num_field() and tep_print_func_field() functions return 1 on success, -1 in case of an error or 0 if the print buffer s is full.

Example

#include <event-parse.h>
#include <trace-seq.h>
...
struct tep_handle *tep = tep_alloc();
...
struct trace_seq seq;
trace_seq_init(&seq);
struct tep_event *event = tep_find_event_by_name(tep, "timer", "hrtimer_start");
...
void process_record(struct tep_record *record)
{
        struct tep_format_field *field_pid = tep_find_common_field(event, "common_pid");

        trace_seq_reset(&seq);

        /* Print the value of "common_pid" */
        tep_print_field_content(&seq, record->data, record->size, field_pid);

        /* Print all fields of the "hrtimer_start" event */
        tep_print_fields(&seq, record->data, record->size, event);

        /* Print the value of "expires" field with custom format string */
        tep_print_num_field(&seq, " timer expires in %llu ", event, "expires", record, 0);

        /* Print the address and the name of "function" field with custom format string */
        tep_print_func_field(&seq, " timer function is %s ", event, "function", record, 0);
 }
 ...

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

Referenced By

The man pages tep_print_fields(3), tep_print_func_field(3), tep_print_num_field(3), tep_record_print_fields(3) and tep_record_print_selected_fields(3) are aliases of tep_print_field_content(3).

07/21/2022 libtraceevent 1.5.3 libtraceevent Manual