LIBTRACEEVENT(3)             libtraceevent Manual             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
       #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

libtraceevent                     01/13/2024                  LIBTRACEEVENT(3)