1vprintf(3C) Standard C Library Functions vprintf(3C)
2
6 vprintf, vfprintf, vsprintf, vsnprintf, vasprintf - print formatted
7 output of a variable argument list
8
10 #include <stdio.h>
11 #include <stdarg.h>
12 int vprintf(const char *format, va_list ap);
14 int vfprintf(FILE *stream, const char *format, va_list ap);
17 int vsprintf(char *s, const char *format, va_list ap);
20 int vsnprintf(char *s, size_t n, const char *format, va_list ap);
23 int vasprintf(char **ret, const char *format, va_list ap);
26
29 The vprintf(), vfprintf(), vsprintf(), vsnprintf(), and vasprintf()
30 functions are the same as printf(), fprintf(), sprintf(), snprintf(),
31 and asprintf(), respectively, except that instead of being called with
32 a variable number of arguments, they are called with an argument list
33 as defined in the <stdarg.h> header. See printf(3C).
34 The <stdarg.h> header defines the type va_list and a set of macros for
37 advancing through a list of arguments whose number and types may vary.
38 The argument ap to the vprint family of functions is of type va_list.
39 This argument is used with the <stdarg.h> header file macros
40 va_start(), va_arg(), and va_end() (see stdarg(3EXT)). The EXAMPLES
41 section below demonstrates the use of va_start() and va_end() with
42 vprintf().
43 The macro va_alist() is used as the parameter list in a function defi‐
46 nition, as in the function called error() in the example below. The
47 macro va_start(ap, name), where ap is of type va_list and name is the
48 rightmost parameter (just before ...), must be called before any
49 attempt to traverse and access unnamed arguments is made. The
50 va_end(ap) macro must be invoked when all desired arguments have been
51 accessed. The argument list in ap can be traversed again if va_start()
52 is called again after va_end(). In the example below, the error() argu‐
53 ments (arg1, arg2, ...) are passed to vfprintf() in the argument ap.
54
56 Refer to printf(3C).
57
59 The vprintf() and vfprintf() functions will fail if either the stream
60 is unbuffered or the stream's buffer needed to be flushed and:
61 EFBIG The file is a regular file and an attempt was made to write at
63 or beyond the offset maximum.
64
67 Example 1 Using vprintf() to write an error routine.
68 The following demonstrates how vfprintf() could be used to write an
71 error routine:
72 #include <stdio.h>
75 #include <stdarg.h>
76 . . .
77 /*
78 * error should be called like
79 * error(function_name, format, arg1, ...);
80 */
81 void error(char *function_name, char *format, ...)
82 {
83 va_list ap;
84 va_start(ap, format);
85 /* print out name of function causing error */
86 (void) fprintf(stderr, "ERR in %s: ", function_name);
87 /* print out remainder of message */
88 (void) vfprintf(stderr, format, ap);
89 va_end(ap);
90 (void) abort();
91 }
92
95 See attributes(5) for descriptions of the following attributes:
96 ┌─────────────────────────────┬─────────────────────────────┐
101 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
102 ├─────────────────────────────┼─────────────────────────────┤
103 │Interface Stability │Committed │
104 ├─────────────────────────────┼─────────────────────────────┤
105 │MT-Level │See below. │
106 ├─────────────────────────────┼─────────────────────────────┤
107 │Standard │See below. │
108 └─────────────────────────────┴─────────────────────────────┘
109 All of these functions can be used safely in multithreaded applica‐
112 tions, as long as setlocale(3C) is not being called to change the
113 locale.
114 See standards(5) for the standards conformance of vprintf(),
117 vfprintf(), vsprintf(), and vsnprintf(). The vasprintf() function is
118 modeled on the one that appears in the FreeBSD, NetBSD, and GNU C
119 libraries.
120
122 printf(3C), attributes(5), stdarg(3EXT), attributes(5), standards(5)
123
125 The vsnprintf() return value when n = 0 was changed in the Solaris 10
126 release. The change was based on the SUSv3 specification. The previous
127 behavior was based on the initial SUSv2 specification, where
128 vsnprintf() when n = 0 returns an unspecified value less than 1.
129SunOS 5.11 7 Jan 2009 vprintf(3C)