1LIBTRACEEVENT(3) libtraceevent Manual LIBTRACEEVENT(3)
2
6 trace_seq_init, trace_seq_destroy, trace_seq_reset,
7 trace_seq_terminate, trace_seq_putc, trace_seq_puts, trace_seq_printf,
8 trace_seq_vprintf, trace_seq_do_fprintf, trace_seq_do_printf -
9 Initialize / destroy a trace sequence.
10
12 #include <event-parse.h>
13 #include <trace-seq.h>
14 void trace_seq_init(struct trace_seq *s);
16 void trace_seq_destroy(struct trace_seq *s);
17 void trace_seq_reset(struct trace_seq *s);
18 void trace_seq_terminate(struct trace_seq *s);
19 int trace_seq_putc(struct trace_seq *s, unsigned char c);
20 int trace_seq_puts(struct trace_seq *s, const char *str);
21 int trace_seq_printf(struct trace_seq *s, const char *fmt, ...);
22 int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args);
23 int trace_seq_do_printf(struct trace_seq *s);
24 int trace_seq_do_fprintf(struct trace_seq *s, FILE *fp);
25
27 Trace sequences are used to allow a function to call several other
28 functions to create a string of data to use.
29 The trace_seq_init() function initializes the trace sequence s.
31 The trace_seq_destroy() function destroys the trace sequence s and
33 frees all its resources that it had used.
34 The trace_seq_reset() function re-initializes the trace sequence s. All
36 characters already written in s will be deleted.
37 The trace_seq_terminate() function terminates the trace sequence s. It
39 puts the null character '\0' at the end of the buffer.
40 The trace_seq_putc() function puts a single character c in the trace
42 sequence s.
43 The trace_seq_puts() function puts a NULL terminated string str in the
45 trace sequence s.
46 The trace_seq_printf() function puts a formated string fmt _with
48 variable arguments _... in the trace sequence s.
49 The trace_seq_vprintf() function puts a formated string fmt _with list
51 of arguments _args in the trace sequence s.
52 The trace_seq_do_printf() function prints the buffer of trace sequence
54 s to the standard output stdout.
55 The trace_seq_do_fprintf() function prints the buffer of trace sequence
57 s to the given file fp.
58
60 Both trace_seq_putc() and trace_seq_puts() functions return the number
61 of characters put in the trace sequence, or 0 in case of an error
62 Both trace_seq_printf() and trace_seq_vprintf() functions return 0 if
64 the trace oversizes the buffer’s free space, the number of characters
65 printed, or a negative value in case of an error.
66 Both trace_seq_do_printf() and trace_seq_do_fprintf() functions return
68 the number of printed characters, or -1 in case of an error.
69
71 #include <event-parse.h>
72 #include <trace-seq.h>
73 ...
74 struct trace_seq seq;
75 trace_seq_init(&seq);
76 ...
77 void foo_seq_print(struct trace_seq *tseq, char *format, ...)
78 {
79 va_list ap;
80 va_start(ap, format);
81 if (trace_seq_vprintf(tseq, format, ap) <= 0) {
82 /* Failed to print in the trace sequence */
83 }
84 va_end(ap);
85 }
86 trace_seq_reset(&seq);
88 char *str = " MAN page example";
90 if (trace_seq_puts(&seq, str) != strlen(str)) {
91 /* Failed to put str in the trace sequence */
92 }
93 if (trace_seq_putc(&seq, ':') != 1) {
94 /* Failed to put ':' in the trace sequence */
95 }
96 if (trace_seq_printf(&seq, " trace sequence: %d", 1) <= 0) {
97 /* Failed to print in the trace sequence */
98 }
99 foo_seq_print( &seq, " %d\n", 2);
100 trace_seq_terminate(&seq);
102 ...
103 if (trace_seq_do_printf(&seq) < 0 ) {
105 /* Failed to print the sequence buffer to the standard output */
106 }
107 FILE *fp = fopen("trace.txt", "w");
108 if (trace_seq_do_fprintf(&seq, fp) < 0 ) [
109 /* Failed to print the sequence buffer to the trace.txt file */
110 }
111 trace_seq_destroy(&seq);
113 ...
114
116 event-parse.h
117 Header file to include in order to have access to the library APIs.
118 trace-seq.h
119 Header file to include in order to have access to trace sequences related APIs.
120 -ltraceevent
121 Linker switch to add when building a program that uses the library.
122
124 libtraceevent(3), trace-cmd(1)
125
127 Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
128 Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
129
131 Report bugs to <linux-trace-devel@vger.kernel.org[3]>
132
134 libtraceevent is Free Software licensed under the GNU LGPL 2.1
135
137 https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
138
140 1. rostedt@goodmis.org
141 mailto:rostedt@goodmis.org
142 2. tz.stoyanov@gmail.com
144 mailto:tz.stoyanov@gmail.com
145 3. linux-trace-devel@vger.kernel.org
147 mailto:linux-trace-devel@vger.kernel.org
148libtraceevent 1.1.1 02/08/2021 LIBTRACEEVENT(3)