tools lib traceevent: Man pages for get field value APIs
Create man pages for libtraceevent APIs: tep_get_any_field_val(), tep_get_common_field_val(), tep_get_field_val(), tep_get_field_raw() Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: linux-trace-devel@vger.kernel.org Link: http://lore.kernel.org/linux-trace-devel/20190503091119.23399-19-tstoyanov@vmware.com Link: http://lkml.kernel.org/r/20190510200108.885426878@goodmis.org Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Tzvetomir Stoyanov
Arnaldo Carvalho de Melo
parent
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libtraceevent(3)
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================
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NAME
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----
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tep_get_any_field_val, tep_get_common_field_val, tep_get_field_val,
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tep_get_field_raw - Get value of a field.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <event-parse.h>*
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*#include <trace-seq.h>*
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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_);
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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_);
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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_);
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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_);
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--
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DESCRIPTION
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-----------
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These functions can be used to find a field and retrieve its value.
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The _tep_get_any_field_val()_ function searches in the _record_ for a field
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with _name_, part of the _event_. If the field is found, its value is stored in
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_val_. If there is an error and _err_ is not zero, then an error string is
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written into _s_.
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The _tep_get_common_field_val()_ function does the same as
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_tep_get_any_field_val()_, but searches only in the common fields. This works
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for any event as all events include the common fields.
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The _tep_get_field_val()_ function does the same as _tep_get_any_field_val()_,
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but searches only in the event specific fields.
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The _tep_get_field_raw()_ function searches in the _record_ for a field with
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_name_, part of the _event_. If the field is found, a pointer to where the field
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exists in the record's raw data is returned. The size of the data is stored in
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_len_. If there is an error and _err_ is not zero, then an error string is
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written into _s_.
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RETURN VALUE
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------------
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The _tep_get_any_field_val()_, _tep_get_common_field_val()_ and
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_tep_get_field_val()_ functions return 0 on success, or -1 in case of an error.
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The _tep_get_field_raw()_ function returns a pointer to field's raw data, and
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places the length of this data in _len_. In case of an error NULL is returned.
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EXAMPLE
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-------
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[source,c]
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--
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#include <event-parse.h>
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#include <trace-seq.h>
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...
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struct tep_handle *tep = tep_alloc();
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...
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struct tep_event *event = tep_find_event_by_name(tep, "kvm", "kvm_exit");
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...
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void process_record(struct tep_record *record)
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{
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int len;
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char *comm;
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struct tep_event_format *event;
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unsigned long long val;
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event = tep_find_event_by_record(pevent, record);
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if (event != NULL) {
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if (tep_get_common_field_val(NULL, event, "common_type",
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record, &val, 0) == 0) {
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/* Got the value of common type field */
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}
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if (tep_get_field_val(NULL, event, "pid", record, &val, 0) == 0) {
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/* Got the value of pid specific field */
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}
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comm = tep_get_field_raw(NULL, event, "comm", record, &len, 0);
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if (comm != NULL) {
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/* Got a pointer to the comm event specific field */
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}
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}
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}
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--
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FILES
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-----
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[verse]
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--
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*event-parse.h*
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Header file to include in order to have access to the library APIs.
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*trace-seq.h*
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Header file to include in order to have access to trace sequences
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related APIs. Trace sequences are used to allow a function to call
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several other functions to create a string of data to use.
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*-ltraceevent*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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_libtraceevent(3)_, _trace-cmd(1)_
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtraceevent is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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