tools lib traceevent: Man pages for trace sequences APIs

libtraceevent(3)

================

NAME

----

trace_seq_init, trace_seq_destroy, trace_seq_reset, trace_seq_terminate,

trace_seq_putc, trace_seq_puts, trace_seq_printf, trace_seq_vprintf,

trace_seq_do_fprintf, trace_seq_do_printf -

Initialize / destroy a trace sequence.

SYNOPSIS

--------

[verse]

--

*#include <event-parse.h>*

*#include <trace-seq.h>*

void *trace_seq_init*(struct trace_seq pass:[*]_s_);

void *trace_seq_destroy*(struct trace_seq pass:[*]_s_);

void *trace_seq_reset*(struct trace_seq pass:[*]_s_);

void *trace_seq_terminate*(struct trace_seq pass:[*]_s_);

int *trace_seq_putc*(struct trace_seq pass:[*]_s_, unsigned char _c_);

int *trace_seq_puts*(struct trace_seq pass:[*]_s_, const char pass:[*]_str_);

int *trace_seq_printf*(struct trace_seq pass:[*]_s_, const char pass:[*]_fmt_, _..._);

int *trace_seq_vprintf*(struct trace_seq pass:[*]_s_, const char pass:[*]_fmt_, va_list _args_);

int *trace_seq_do_printf*(struct trace_seq pass:[*]_s_);

int *trace_seq_do_fprintf*(struct trace_seq pass:[*]_s_, FILE pass:[*]_fp_);

--

DESCRIPTION

-----------

Trace sequences are used to allow a function to call several other functions

to create a string of data to use.

The _trace_seq_init()_ function initializes the trace sequence _s_.

The _trace_seq_destroy()_ function destroys the trace sequence _s_ and frees

all its resources that it had used.

The _trace_seq_reset()_ function re-initializes the trace sequence _s_. All

characters already written in _s_ will be deleted.

The _trace_seq_terminate()_ function terminates the trace sequence _s_. It puts

the null character pass:['\0'] at the end of the buffer.

The _trace_seq_putc()_ function puts a single character _c_ in the trace

sequence _s_.

The _trace_seq_puts()_ function puts a NULL terminated string _str_ in the

trace sequence _s_.

The _trace_seq_printf()_ function puts a formated string _fmt _with

variable arguments _..._ in the trace sequence _s_.

The _trace_seq_vprintf()_ function puts a formated string _fmt _with

list of arguments _args_ in the trace sequence _s_.

The _trace_seq_do_printf()_ function prints the buffer of trace sequence _s_ to

the standard output stdout.

The _trace_seq_do_fprintf()_ function prints the buffer of trace sequence _s_

to the given file _fp_.

RETURN VALUE

------------

Both _trace_seq_putc()_ and _trace_seq_puts()_ functions return the number of

characters put in the trace sequence, or 0 in case of an error

Both _trace_seq_printf()_ and _trace_seq_vprintf()_ functions return 0 if the

trace oversizes the buffer's free space, the number of characters printed, or

a negative value in case of an error.

Both _trace_seq_do_printf()_ and _trace_seq_do_fprintf()_ functions return the

number of printed characters, or -1 in case of an error.

EXAMPLE

-------

[source,c]

--

#include <event-parse.h>

#include <trace-seq.h>

...

struct trace_seq seq;

trace_seq_init(&seq);

...

void foo_seq_print(struct trace_seq *tseq, char *format, ...)

{

	va_list ap;

	va_start(ap, format);

	if (trace_seq_vprintf(tseq, format, ap) <= 0) {

		/* Failed to print in the trace sequence */

	}

	va_end(ap);

}

trace_seq_reset(&seq);

char *str = " MAN page example";

if (trace_seq_puts(&seq, str) != strlen(str)) {

	/* Failed to put str in the trace sequence */

}

if (trace_seq_putc(&seq, ':') != 1) {

	/* Failed to put ':' in the trace sequence */

}

if (trace_seq_printf(&seq, " trace sequence: %d", 1) <= 0) {

	/* Failed to print in the trace sequence */

}

foo_seq_print( &seq, "  %d\n", 2);

trace_seq_terminate(&seq);

...

if (trace_seq_do_printf(&seq) < 0 ) {

	/* Failed to print the sequence buffer to the standard output */

}

FILE *fp = fopen("trace.txt", "w");

if (trace_seq_do_fprintf(&seq, fp) < 0 ) [

	/* Failed to print the sequence buffer to the trace.txt file */

}

trace_seq_destroy(&seq);

...

--

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.

*-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