printf(9) - NetBSD Manual Pages

KPRINTF(9)             NetBSD Kernel Developer's Manual             KPRINTF(9)


NAME

     printf, snprintf, vprintf, vsnprintf, uprintf, ttyprintf, tprintf -- ker-
     nel formatted output conversion


SYNOPSIS

     #include <sys/systm.h>

     void
     printf(const char *format, ...);

     void
     printf_nolog(const char *format, ...);

     int
     snprintf(char *buf, size_t size, const char *format, ...);

     void
     vprintf(const char *format, va_list ap);

     int
     vsnprintf(char *buf, size_t size, const char *format, va_list ap);

     void
     uprintf(const char *format, ...);

     void
     ttyprintf(struct tty *tty, const char *format, ...);

     #include <sys/tprintf.h>

     tpr_t
     tprintf_open(struct proc *p);

     void
     tprintf(tpr_t tpr, const char *format, ...);

     void
     tprintf_close(tpr_t tpr);

     void
     aprint_normal(const char *format, ...);

     void
     aprint_naive(const char *format, ...);

     void
     aprint_verbose(const char *format, ...);

     void
     aprint_debug(const char *format, ...);

     void
     aprint_error(const char *format, ...);

     int
     aprint_get_error_count(void);


DESCRIPTION

     The printf() family of functions allows the kernel to send formatted mes-
     sages to various output devices.  The functions printf() and vprintf()
     send formatted strings to the system console.  The printf_nolog() func-
     tion is identical to printf(), except it does not send the data to the
     system log.  The functions snprintf() and vsnprintf() write output to a
     string buffer.  These four functions work similarly to their user space
     counterparts, and are not described in detail here.

     The functions uprintf() and ttyprintf() send formatted strings to the
     current process's controlling tty and a specific tty, respectively.

     The tprintf() function sends formatted strings to a process's controlling
     tty, via a handle of type tpr_t.  This allows multiple write operations
     to the tty with a guarantee that the tty will be valid across calls.  A
     handle is acquired by calling tprintf_open() with the target process as
     an argument.  This handle must be closed with a matching call to
     tprintf_close().

     The functions aprint_normal(), aprint_naive(), aprint_verbose(),
     aprint_debug(), and aprint_error() are intended to be used to print auto-
     configuration messages, and change their behavior based on flags in the
     ``boothowto'' variable:

     aprint_normal()   Sends to the console unless AB_QUIET is set.  Always
                       sends to the log.

     aprint_naive()    Sends to the console only if AB_QUIET is set.  Never
                       sends to the log.

     aprint_verbose()  Sends to the console only if AB_VERBOSE is set.  Always
                       sends to the log.

     aprint_debug()    Sends to the console and the log only if AB_DEBUG is
                       set.

     aprint_error()    Like aprint_normal(), but also keeps track of the num-
                       ber of times called.  This allows a subsystem to report
                       the number of errors that occurred during a quiet or
                       silent initialization phase.  The
                       aprint_get_error_count() function reports the number of
                       errors and resets the counter to 0.

     If AB_SILENT is set, none of the autoconfiguration message printing rou-
     tines send output to the console.  The AB_VERBOSE and AB_DEBUG flags
     override AB_SILENT.


RETURN VALUES

     The snprintf() and vsnprintf() functions return the number of characters
     placed in the buffer buf.  This is different to the user-space functions
     of the same name.

     The tprintf_open() function returns NULL if no terminal handle could be
     acquired.


SEE ALSO

     printf(1), printf(3), bitmask_snprintf(9)


CODE REFERENCES

     sys/kern/subr_prf.c


HISTORY

     The sprintf() and vsprintf() unsized string formatting functions are sup-
     ported for compatibility only, and are not documented here.  New code
     should use the size-limited snprintf() and vsnprintf() functions instead.

     In NetBSD 1.5 and earlier, printf() supported more format strings than
     the user space printf().  These nonstandard format strings are no longer
     supported.  For the functionality provided by the former %b format
     string, see bitmask_snprintf(9).

     The aprint_normal(), aprint_naive(), aprint_verbose(), and aprint_debug()
     functions first appeared in BSD/OS.


BUGS

     The uprintf() and ttyprintf() functions should be used sparingly, if at
     all.  Where multiple lines of output are required to reach a process's
     controlling terminal, tprintf() is preferred.

NetBSD 4.0                     January 15, 2006                     NetBSD 4.0