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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |EXAMPLE |FILES |SEE ALSO |AUTHOR |REPORTING BUGS |LICENSE |RESOURCES |NOTES |COLOPHON | |
LIBTRACEEVENT(3) libtraceevent ManualLIBTRACEEVENT(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> voidtrace_seq_init(struct trace_seq *s); voidtrace_seq_destroy(struct trace_seq *s); voidtrace_seq_reset(struct trace_seq *s); voidtrace_seq_terminate(struct trace_seq *s); inttrace_seq_putc(struct trace_seq *s, unsigned charc); inttrace_seq_puts(struct trace_seq *s, const char *str); inttrace_seq_printf(struct trace_seq *s, const char *fmt,...); inttrace_seq_vprintf(struct trace_seq *s, const char *fmt, va_listargs); inttrace_seq_do_printf(struct trace_seq *s); inttrace_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. Thetrace_seq_init()function initializes the trace sequences. Thetrace_seq_destroy()function destroys the trace sequences and frees all its resources that it had used. Thetrace_seq_reset()function re-initializes the trace sequences. All characters already written ins will be deleted. Thetrace_seq_terminate()function terminates the trace sequences. It puts the null character '\0' at the end of the buffer. Thetrace_seq_putc()function puts a single characterc in the trace sequences. Thetrace_seq_puts()function puts a NULL terminated stringstr in the trace sequences. Thetrace_seq_printf()function puts a formated stringfmt _withvariable arguments _... in the trace sequences. Thetrace_seq_vprintf()function puts a formated stringfmt _withlist of arguments _args in the trace sequences. Thetrace_seq_do_printf()function prints the buffer of trace sequences to the standard output stdout. Thetrace_seq_do_fprintf()function prints the buffer of trace sequences to the given filefp.
Bothtrace_seq_putc()andtrace_seq_puts()functions return the number of characters put in the trace sequence, or 0 in case of an error Bothtrace_seq_printf()andtrace_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. Bothtrace_seq_do_printf()andtrace_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.
libtraceevent(3),trace-cmd(1)
Steven Rostedt<rostedt@goodmis.org[1]>, author oflibtraceevent.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/
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
This page is part of thelibtraceevent (Linux kernel trace event library) project. Information about the project can be found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report for this manual page, see ⟨https://www.trace-cmd.org/⟩. This page was obtained from the project's upstream Git repository ⟨https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-05-30.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orglibtraceevent 1.7.3 09/24/2023LIBTRACEEVENT(3)HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |