libtraceevent-field_print.txt (4262B)
1libtraceevent(3) 2================ 3 4NAME 5---- 6tep_print_field, tep_print_fields, tep_print_num_field, tep_print_func_field - 7Print the field content. 8 9SYNOPSIS 10-------- 11[verse] 12-- 13*#include <event-parse.h>* 14*#include <trace-seq.h>* 15 16void *tep_print_field*(struct trace_seq pass:[*]_s_, void pass:[*]_data_, struct tep_format_field pass:[*]_field_); 17void *tep_print_fields*(struct trace_seq pass:[*]_s_, void pass:[*]_data_, int _size_, struct tep_event pass:[*]_event_); 18int *tep_print_num_field*(struct trace_seq pass:[*]_s_, const char pass:[*]_fmt_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, int _err_); 19int *tep_print_func_field*(struct trace_seq pass:[*]_s_, const char pass:[*]_fmt_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, int _err_); 20-- 21 22DESCRIPTION 23----------- 24These functions print recorded field's data, according to the field's type. 25 26The _tep_print_field()_ function extracts from the recorded raw _data_ value of 27the _field_ and prints it into _s_, according to the field type. 28 29The _tep_print_fields()_ prints each field name followed by the record's field 30value according to the field's type: 31[verse] 32-- 33"field1_name=field1_value field2_name=field2_value ..." 34-- 35It iterates all fields of the _event_, and calls _tep_print_field()_ for each of 36them. 37 38The _tep_print_num_field()_ function prints a numeric field with given format 39string. A search is performed in the _event_ for a field with _name_. If such 40field is found, its value is extracted from the _record_ and is printed in the 41_s_, according to the given format string _fmt_. If the argument _err_ is 42non-zero, and an error occures - it is printed in the _s_. 43 44The _tep_print_func_field()_ function prints a function field with given format 45string. A search is performed in the _event_ for a field with _name_. If such 46field is found, its value is extracted from the _record_. The value is assumed 47to be a function address, and a search is perform to find the name of this 48function. The function name (if found) and its address are printed in the _s_, 49according to the given format string _fmt_. If the argument _err_ is non-zero, 50and an error occures - it is printed in _s_. 51 52RETURN VALUE 53------------ 54The _tep_print_num_field()_ and _tep_print_func_field()_ functions return 1 55on success, -1 in case of an error or 0 if the print buffer _s_ is full. 56 57EXAMPLE 58------- 59[source,c] 60-- 61#include <event-parse.h> 62#include <trace-seq.h> 63... 64struct tep_handle *tep = tep_alloc(); 65... 66struct trace_seq seq; 67trace_seq_init(&seq); 68struct tep_event *event = tep_find_event_by_name(tep, "timer", "hrtimer_start"); 69... 70void process_record(struct tep_record *record) 71{ 72 struct tep_format_field *field_pid = tep_find_common_field(event, "common_pid"); 73 74 trace_seq_reset(&seq); 75 76 /* Print the value of "common_pid" */ 77 tep_print_field(&seq, record->data, field_pid); 78 79 /* Print all fields of the "hrtimer_start" event */ 80 tep_print_fields(&seq, record->data, record->size, event); 81 82 /* Print the value of "expires" field with custom format string */ 83 tep_print_num_field(&seq, " timer expires in %llu ", event, "expires", record, 0); 84 85 /* Print the address and the name of "function" field with custom format string */ 86 tep_print_func_field(&seq, " timer function is %s ", event, "function", record, 0); 87 } 88 ... 89-- 90 91FILES 92----- 93[verse] 94-- 95*event-parse.h* 96 Header file to include in order to have access to the library APIs. 97*trace-seq.h* 98 Header file to include in order to have access to trace sequences related APIs. 99 Trace sequences are used to allow a function to call several other functions 100 to create a string of data to use. 101*-ltraceevent* 102 Linker switch to add when building a program that uses the library. 103-- 104 105SEE ALSO 106-------- 107_libtraceevent(3)_, _trace-cmd(1)_ 108 109AUTHOR 110------ 111[verse] 112-- 113*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*. 114*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page. 115-- 116REPORTING BUGS 117-------------- 118Report bugs to <linux-trace-devel@vger.kernel.org> 119 120LICENSE 121------- 122libtraceevent is Free Software licensed under the GNU LGPL 2.1 123 124RESOURCES 125--------- 126https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git