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Diffstat (limited to 'tools/lib/traceevent/Documentation/libtraceevent-field_get_val.txt')
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diff --git a/tools/lib/traceevent/Documentation/libtraceevent-field_get_val.txt b/tools/lib/traceevent/Documentation/libtraceevent-field_get_val.txt new file mode 100644 index 000000000..6324f0d48 --- /dev/null +++ b/tools/lib/traceevent/Documentation/libtraceevent-field_get_val.txt @@ -0,0 +1,122 @@ +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 +-------- +[verse] +-- +*#include <event-parse.h>* +*#include <trace-seq.h>* + +int *tep_get_any_field_val*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, unsigned long long pass:[*]_val_, int _err_); +int *tep_get_common_field_val*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, unsigned long long pass:[*]_val_, int _err_); +int *tep_get_field_val*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, unsigned long long pass:[*]_val_, int _err_); +void pass:[*]*tep_get_field_raw*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, int pass:[*]_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 +------- +[source,c] +-- +#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_format *event; + unsigned long long val; + + event = tep_find_event_by_record(pevent, 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 +----- +[verse] +-- +*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 +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*. +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page. +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtraceevent is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git |