NAME
printf, uprintf, tprintf, log — formatted output conversionSYNOPSIS
#include <sys/types.h>#include <sys/systm.h> int
printf(const char *fmt, ...); void
tprintf(struct proc *p, int pri, const char *fmt, ...); int
uprintf(const char *fmt, ...); int
vprintf(const char *fmt, va_list ap); #include <sys/syslog.h> void
log(int pri, const char *fmt, ...); void
vlog(int pri, const char *fmt, va_list ap);
DESCRIPTION
The printf(9) family of functions are similar to the printf(3) family of functions. The different functions each use a different output stream. The uprintf() function outputs to the current process' controlling tty, while printf() writes to the console as well as to the logging facility. The tprintf() function outputs to the tty associated with the process p and the logging facility if pri is not -1. The log() function sends the message to the kernel logging facility, using the log level as indicated by pri, and to the console if no process is yet reading the log. Each of these related functions use the fmt parameter in the same manner as printf(3). However, printf(9) adds two other conversion specifiers. The %b identifier expects two arguments: an int and a char *. These are used as a register value and a print mask for decoding bitmasks. The print mask is made up of two parts: the base and the arguments. The base value is the output base expressed as an integer value; for example, \10 gives octal and \20 gives hexadecimal. The arguments are made up of a sequence of bit identifiers. Each bit identifier begins with an integer value which is the number of the bit (starting from 1) this identifier describes. The rest of the identifier is a string of characters containing the name of the bit. The string is terminated by either the bit number at the start of the next bit identifier orNUL for the last bit
identifier.
The %D identifier is meant to assist in hexdumps.
It requires two arguments: a u_char * pointer
and a char * string. The memory pointed to by
the pointer is output in hexadecimal one byte at a time. The string is used as
a delimiter between individual bytes. If present, a width directive will
specify the number of bytes to display. By default, 16 bytes of data are
output.
The log() function uses
syslog(3) level values
LOG_DEBUG through
LOG_EMERG for its
pri parameter (mistakenly called
‘priority’ here). Alternatively, if a
pri of -1 is given, the message will be
appended to the last log message started by a previous call to
log(). As these messages are generated by the
kernel itself, the facility will always be
LOG_KERN.
RETURN VALUES
The printf() and the uprintf() functions return the number of characters displayed.EXAMPLES
This example demonstrates the use of the %b and %D conversion specifiers. The function
void
printf_test(void)
{
printf("reg=%b\n", 3, "\10\2BITTWO\1BITONE");
printf("out: %4D\n", "AAAA", ":");
}
reg=3<BITTWO,BITONE> out: 41:41:41:41
log(LOG_DEBUG, "%s%d: been there.\n", sc->sc_name, sc->sc_unit);
kern.debug” to the system log.
SEE ALSO
printf(3), syslog(3)| November 18, 2015 | Debian |