{"id":4154,"date":"2022-12-20T17:39:33","date_gmt":"2022-12-20T20:39:33","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/printk-man9\/"},"modified":"2022-12-20T17:39:33","modified_gmt":"2022-12-20T20:39:33","slug":"printk-man9","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/printk-man9\/","title":{"rendered":"printk (man9)"},"content":{"rendered":"

printk<\/h1>\n

NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
AVAILABILITY<\/a>
SEE ALSO<\/a>
AUTHOR<\/a>
BUGS<\/a> <\/p>\n

\n

NAME <\/a> <\/h2>\n

printk \u2212 print messages to console log<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

#include <\/b><\/p>\n

int printk(const char*<\/b>fmt<\/i>, …)<\/b><\/p>\n

DESCRIPTION <\/a> <\/h2>\n

Print a formatted message to the kernel console, much like the printf<\/b> function of the stdio library. Normally, the message is written to the physical console device of the computer, although this behavior can be changed with the register_console<\/b> function. Messages are also stored in a message log book.<\/p>\n

The generated string may also start with a message priority code, which sets the priority of the message. The priority code strings are of the form <\/i> where n is a number from 0 – 7. The following macros are defined in the <\/i> header file:<\/p>\n

KERN_EMERG<\/p>\n

System is unuseable<\/p>\n

KERN_ALERT<\/p>\n

Action must be taken immediately<\/p>\n

KERN_CRIT<\/p>\n

Critical conditions<\/p>\n

KERN_ERR<\/p>\n

Error conditions<\/p>\n

KERN_WARNING<\/p>\n

Warning conditions<\/p>\n

KERN_NOTICE<\/p>\n

Normal but significant condition<\/p>\n

KERN_INFO<\/p>\n

Informational<\/p>\n

KERN_DEBUG<\/p>\n

Debug-level messages<\/p>\n

For example<\/p>\n\n\n
<\/td>\n<\/td>\n\n

printk(KERN_NOTICE “Hello, world.n”);<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

does the expected thing.<\/p>\n

RETURN VALUE <\/a> <\/h2>\n

Returns the number of characters written to the log.<\/p>\n

AVAILABILITY <\/a> <\/h2>\n

Linux 1.0+<\/p>\n

SEE ALSO <\/a> <\/h2>\n

register_console<\/b>(9), syslog<\/b>(2)<\/p>\n

kernel\/printk.c<\/i><\/p>\n

AUTHOR <\/a> <\/h2>\n

Stephen Williams (steve@icarus.com)<\/p>\n

BUGS <\/a> <\/h2>\n

float and double formats are not supported. Floats and doubles do not belong inside the kernel anyhow.<\/p>\n

The printk<\/b> implementation protects itself from interruption, so in principle it can be used in interrupts handlers and critical sections. However, there are no guarantees about the console function that is registered.<\/p>\n

\n","protected":false},"excerpt":{"rendered":"

printk \u2212 print messages to console log <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1222],"tags":[1226,1223,1225,1234],"class_list":["post-4154","post","type-post","status-publish","format-standard","hentry","category-9-rutinas-del-nucleo","tag-1226","tag-kernel","tag-man9","tag-printk"],"gutentor_comment":0,"_links":{"self":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/4154","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/comments?post=4154"}],"version-history":[{"count":0,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/4154\/revisions"}],"wp:attachment":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/media?parent=4154"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/categories?post=4154"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/tags?post=4154"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}