| LIBTRACEEVENT(3) | libtraceevent Manual | LIBTRACEEVENT(3) |
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.
#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);
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.
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.
#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);
...
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.
Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent. Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtraceevent is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
| 01/18/2023 | libtraceevent 1.7.1 |