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>, 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