GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
RedHat 5.2(Apollo) |
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vsnprintf(3) |
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snprintf, vsnprintf − formatted output conversion
#define
_GNU_SOURCE
#include <stdio.h>
int snprintf
( char *str, size_t n,
const char *format, ... );
#include <stdarg.h>
int
vsnprintf ( char *str, size_t n,
const char *format, va_list ap
);
snprintf writes output to the string str, under control of the format string that specifies how subsequent arguments are converted for output. It is similar to sprintf(3), except that n specifies the maximum number of characters to produce. The trailing null character is counted towards this limit, so you should allocate at least n characters for the string str.
vsnprintf is the equivalent of snprintf with the variable argument list specified directly as for vprintf.
If the output was truncated, the return value is -1, otherwise it is the number of characters stored, not including the terminating null.
Here is an example program which dynamically enlarges its output buffer.
/* Construct a
message describing the value of a
variable whose name is NAME and whose value is
VALUE. */
char *
make_message (char *name, char *value)
{
/* Guess we need no more than 100 chars of space. */
int size = 100;
char *buffer = (char *) xmalloc (size);
while (1)
{
/* Try to print in the allocated space. */
int nchars = snprintf (buffer, size,
"value of %s is %s", name, value);
/* If that worked, return the string. */
if (nchars > -1)
return buffer;
/* Else try again with twice as much space. */
size *= 2;
buffer = (char *) xrealloc (buffer, size);
}
}
These are GNU extensions.
printf(3), sprintf(3), vsprintf(3), stdarg(3)
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vsnprintf(3) | |