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Diffstat (limited to 'Documentation/libtracecmd/libtracecmd-record.txt')
| -rw-r--r-- | Documentation/libtracecmd/libtracecmd-record.txt | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/Documentation/libtracecmd/libtracecmd-record.txt b/Documentation/libtracecmd/libtracecmd-record.txt new file mode 100644 index 00000000..aa1a4a66 --- /dev/null +++ b/Documentation/libtracecmd/libtracecmd-record.txt @@ -0,0 +1,138 @@ +libtracecmd(3) +============= + +NAME +---- +tracecmd_read_cpu_first, tracecmd_read_data, tracecmd_read_at, +tracecmd_free_record, tracecmd_get_tep - Read recorded events from a trace file. + +SYNOPSIS +-------- +[verse] +-- +*#include <trace-cmd.h>* + +struct tep_record pass:[*]*tracecmd_read_cpu_first*(struct tracecmd_input pass:[*]_handle_, int _cpu_); +struct tep_record pass:[*]*tracecmd_read_data*(struct tracecmd_input pass:[*]_handle_, int _cpu_); +struct tep_record pass:[*]*tracecmd_read_at*(struct tracecmd_input pass:[*]_handle_, unsigned long long _offset_, int pass:[*]_cpu_); +void *tracecmd_free_record*(struct tep_record pass:[*]_record_); +struct tep_handle pass:[*]*tracecmd_get_tep*(struct tracecmd_input pass:[*]_handle_); +-- + +DESCRIPTION +----------- +This set of APIs can be used to read tracing data from a trace file opened +with _tracecmd_open()(3)_, _tracecmd_open_fd()(3)_ or _tracecmd_open_head()(3)_. + +The _tracecmd_read_cpu_first()_ function reads the first trace record +for a given _cpu_ from a trace file associated with _handle_. The returned +record must be freed with _tracecmd_free_record()_. + +The _tracecmd_read_data()_ function reads the next trace record for +a given _cpu_ from a trace file associated with _handle_ and increments +the read location pointer, so that the next call to _tracecmd_read_data()_ +will not read the same record again. The returned record must be freed +with _tracecmd_free_record()_. + +The _tracecmd_read_at()_ function reads a trace record from a specific +_offset_ within the file associated with _handle_. The CPU on which the +recorded event occurred is stored in the _cpu_. The function does not +change the current read location pointer. The returned record must be +freed with _tracecmd_free_record()_. + +The _tracecmd_free_record()_ function frees a _record_ returned by any +of the _tracecmd_read__ APIs. + +The _tracecmd_get_tep()_ function returns a tep context for a given +_handle_. + +RETURN VALUE +------------ +The _tracecmd_read_cpu_first()_, _tracecmd_read_data()_ and +_tracecmd_read_at()_ functions return a pointer to struct tep_record or +NULL in case of an error.The returned record must be freed with +_tracecmd_free_record()_. + +The _tracecmd_get_tep()_ function returns a pointer to tep context or +NULL if there is no tep context for the given _handle_. The returned +tep pointer must *not* be freed. + +EXAMPLE +------- +[source,c] +-- +#include <trace-cmd.h> +... +struct tracecmd_input *handle = tracecmd_open("trace.dat"); + if (!handle) { + /* Failed to open trace.dat file */ + } +... +unsigned long long offset = 0; +struct tep_record *rec; +int cpu = 0; + rec = tracecmd_read_cpu_first(handle, cpu); + while (rec) { + ... + if ( /* some interesting record noticed */) { + /* store the offset of the interesting record */ + offset = rec->offset; + } + ... + tracecmd_free_record(rec); + rec = tracecmd_read_data(handle, cpu); + } + ... + if (offset) { + rec = tracecmd_read_at(handle, offset, &cpu); + if (rec) { + /* Got record at offset on cpu */ + ... + tracecmd_free_record(rec); + } + } + +... + tracecmd_close(hadle); + +-- +FILES +----- +[verse] +-- +*trace-cmd.h* + Header file to include in order to have access to the library APIs. +*-ltracecmd* + Linker switch to add when building a program that uses the library. +-- + +SEE ALSO +-------- +_libtracefs(3)_, +_libtraceevent(3)_, +_trace-cmd(1)_ +_trace-cmd.dat(5)_ + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org> +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com> +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtracecmd is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/ + +COPYING +------- +Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). |