{"id":7057,"date":"2022-12-20T19:34:48","date_gmt":"2022-12-20T22:34:48","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/ftok-man3\/"},"modified":"2022-12-20T19:34:48","modified_gmt":"2022-12-20T22:34:48","slug":"ftok-man3","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/ftok-man3\/","title":{"rendered":"FTOK (man3)"},"content":{"rendered":"

FTOK<\/h1>\n

NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
ATTRIBUTES<\/a>
CONFORMING TO<\/a>
NOTES<\/a>
EXAMPLES<\/a>
SEE ALSO<\/a>
COLOPHON<\/a> <\/p>\n

\n

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

ftok \u2212 convert a pathname and a project identifier to a System V IPC key<\/p>\n

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

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

key_t ftok(const char *<\/b>pathname<\/i>, int<\/b> proj_id<\/i>);<\/b><\/p>\n

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

The ftok<\/b>() function uses the identity of the file named by the given pathname<\/i> (which must refer to an existing, accessible file) and the least significant 8 bits of proj_id<\/i> (which must be nonzero) to generate a key_t<\/i> type System V IPC key, suitable for use with msgget<\/b>(2), semget<\/b>(2), or shmget<\/b>(2).<\/p>\n

The resulting value is the same for all pathnames that name the same file, when the same value of proj_id<\/i> is used. The value returned should be different when the (simultaneously existing) files or the project IDs differ.<\/p>\n

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

On success, the generated key_t<\/i> value is returned. On failure \u22121 is returned, with errno<\/i> indicating the error as for the stat<\/b>(2) system call.<\/p>\n

ATTRIBUTES <\/a> <\/h2>\n

For an explanation of the terms used in this section, see attributes<\/b>(7).<\/p>\n\n\n\n
<\/td>\n <\/td>\n <\/td>\n<\/td>\n<\/td>\n <\/td>\n<\/tr>\n
<\/td>\n<\/td>\n <\/td>\n<\/td>\n<\/td>\n <\/td>\n<\/tr>\n<\/table>\n

\"Image<\/p>\n

CONFORMING TO <\/a> <\/h2>\n

POSIX.1-2001, POSIX.1-2008.<\/p>\n

NOTES <\/a> <\/h2>\n

On some ancient systems, the prototype was:<\/p>\n

key_t ftok(char *<\/b>pathname<\/i>, char<\/b> proj_id<\/i>);<\/b><\/p>\n

Today, proj_id<\/i> is an int<\/i>, but still only 8 bits are used. Typical usage has an ASCII character proj_id<\/i>, that is why the behavior is said to be undefined when proj_id<\/i> is zero.<\/p>\n

Of course, no guarantee can be given that the resulting key_t<\/i> is unique. Typically, a best-effort attempt combines the given proj_id<\/i> byte, the lower 16 bits of the inode number, and the lower 8 bits of the device number into a 32-bit result. Collisions may easily happen, for example between files on \/dev\/hda1<\/i> and files on \/dev\/sda1<\/i>.<\/p>\n

EXAMPLES <\/a> <\/h2>\n

See semget<\/b>(2).<\/p>\n

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

msgget<\/b>(2), semget<\/b>(2), shmget<\/b>(2), stat<\/b>(2), sysvipc<\/b>(7)<\/p>\n

COLOPHON <\/a> <\/h2>\n

This page is part of release 5.10 of the Linux man-pages<\/i> project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https:\/\/www.kernel.org\/doc\/man\u2212pages\/.<\/p>\n

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

ftok \u2212 convert a pathname and a project identifier to a System V IPC key <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2536],"tags":[2538,2138,3007],"class_list":["post-7057","post","type-post","status-publish","format-standard","hentry","category-3-llamadas-de-bibliotecas","tag-2538","tag-ftok","tag-man3"],"gutentor_comment":0,"_links":{"self":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/7057","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=7057"}],"version-history":[{"count":0,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/7057\/revisions"}],"wp:attachment":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/media?parent=7057"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/categories?post=7057"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/tags?post=7057"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}