KPRINTF(9) NetBSD Kernel Developer's Manual KPRINTF(9)
NAME
device_printf, printf, printf_nolog, printf_nostamp, snprintf, vasprintf, vprintf, vsnprintf, uprintf, ttyprintf, tprintf_open, tprintf, tprintf_close, aprint_normal, aprint_naive, aprint_verbose, aprint_debug, aprint_error, aprint_normal_dev, aprint_naive_dev, aprint_verbose_dev, aprint_debug_dev, aprint_error_dev, aprint_normal_ifnet, aprint_naive_ifnet, aprint_verbose_ifnet, aprint_debug_ifnet, aprint_error_ifnet, aprint_get_error_count -- kernel formatted output conversion
SYNOPSIS
#include <sys/systm.h> void device_printf(device_t, const char *format, ...); void printf(const char *format, ...); void printf_nolog(const char *format, ...); void printf_nostamp(const char *format, ...); int snprintf(char *buf, size_t size, const char *format, ...); int vasprintf(char **buf, const char *format, va_list ap); 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, ...); void aprint_normal_dev(device_t, const char *format, ...); void aprint_naive_dev(device_t, const char *format, ...); void aprint_verbose_dev(device_t, const char *format, ...); void aprint_debug_dev(device_t, const char *format, ...); void aprint_error_dev(device_t, const char *format, ...); void aprint_normal_ifnet(struct ifnet *, const char *format, ...); void aprint_naive_ifnet(struct ifnet *, const char *format, ...); void aprint_verbose_ifnet(struct ifnet *, const char *format, ...); void aprint_debug_ifnet(struct ifnet *, const char *format, ...); void aprint_error_ifnet(struct ifnet *, 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 device_printf() func- tion is identical to printf(), except that it prefixes the log message with the corresponding device name. The printf_nolog() function is iden- tical to printf(), except it does not send the data to the system log. The printf_nostamp() function is identical to printf(), except it does not prefix the output with a timestamp. The functions snprintf(), vasprintf(), and vsnprintf() write output to a string buffer. These five functions work similarly to their user space counterparts, and are not described in detail here. The vasprintf() function allocates memory with kmem_alloc(9) and it is the caller's responsibility to free the returned string with kmem_free(9). 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 autoconf(9) messages. Their verbosity depends on flags set in the boothowto variable, through options passed during bootstrap; see boothowto(9) and Interactive mode in boot(8): AB_SILENT silent mode, enabled by boot -z. AB_QUIET quiet mode, enabled by boot -q. AB_VERBOSE verbose mode, enabled by boot -v. AB_DEBUG debug mode, enabled by boot -x. The aprint_*() functions have the following behaviour, based on the above mentioned flags: 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 number of times called. This allows a subsystem to report the number of errors that occurred during a quiet or silent initialization phase. For the aprint_*() functions there are two additional families of func- tions with the suffixes _dev and _ifnet which work like their counter- parts without the suffixes, except that they take a device_t and struct ifnet *, respectively, as first argument, and prefix the log message with the corresponding device or interface name. 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 that would have been placed in the buffer buf. if there was enough space in the buffer, not including the trailing NUL character used to terminate output strings like the user-space functions of the same name. The tprintf_open() function returns NULL if no terminal handle could be acquired.
CODE REFERENCES
sys/kern/subr_prf.c
SEE ALSO
printf(1), printf(3), snprintb(3), boot(8), autoconf(9), boothowto(9)
HISTORY
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 snprintb(3). 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 10.1 March 10, 2021 NetBSD 10.1
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