Man page - trace_seq_init(3)

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Manual

LIBTRACEEVENT

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
EXAMPLE
FILES
SEE ALSO
AUTHOR
REPORTING BUGS
LICENSE
RESOURCES
NOTES

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

#include <event-parse.h>
#include <trace-seq.h>

void trace_seq_init (struct trace_seq * s );
void trace_seq_destroy (struct trace_seq * s );
void trace_seq_reset (struct trace_seq * s );
void trace_seq_terminate (struct trace_seq * s );
int trace_seq_putc (struct trace_seq * s , unsigned char c );
int trace_seq_puts (struct trace_seq * s , const char * str );
int trace_seq_printf (struct trace_seq * s , const char * fmt , ... );
int trace_seq_vprintf (struct trace_seq * s , const char * fmt , va_list args );
int trace_seq_do_printf (struct trace_seq * s );
int trace_seq_do_fprintf (struct trace_seq * s , FILE * 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 '\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

#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

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

Steven Rostedt < rostedt@goodmis.org [1] >, author of libtraceevent .
Tzvetomir Stoyanov < tz.stoyanov@gmail.com [2] >, author of this man page.

REPORTING BUGS

Report bugs to < linux-trace-devel@vger.kernel.org [3] >

LICENSE

libtraceevent is Free Software licensed under the GNU LGPL 2.1

RESOURCES

https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/

NOTES

1.

rostedt@goodmis.org

mailto:rostedt@goodmis.org

2.

tz.stoyanov@gmail.com

mailto:tz.stoyanov@gmail.com

3.

linux-trace-devel@vger.kernel.org

mailto:linux-trace-devel@vger.kernel.org