from small one page howto to huge articles all in one place
 

search text in:





Poll
Which filesystem do you use?






poll results

Last additions:
using iotop to find disk usage hogs

using iotop to find disk usage hogs

words:

887

views:

85994

userrating:

average rating: 1.7 (82 votes) (1=very good 6=terrible)


May 25th. 2007:
Words

486

Views

202360

why adblockers are bad


Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

words:

161

views:

84349

userrating:

average rating: 1.3 (27 votes) (1=very good 6=terrible)


April, 26th. 2006:

Druckversion
You are here: manpages





INSQUE

Section: Linux Programmer's Manual (3)
Updated: 2014-08-19
Index Return to Main Contents
 

NAME

insque, remque - insert/remove an item from a queue  

SYNOPSIS

#include <search.h>

void insque(void *elem, void *prev);

void remque(void *elem);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

insque(), remque():

_SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
 

DESCRIPTION

The insque() and remque() functions manipulate doubly-linked lists. Each element in the list is a structure of which the first two elements are a forward and a backward pointer. The linked list may be linear (i.e., NULL forward pointer at the end of the list and NULL backward pointer at the start of the list) or circular.

The insque() function inserts the element pointed to by elem immediately after the element pointed to by prev.

If the list is linear, then the call insque(elem, NULL) can be used to insert the initial list element, and the call sets the forward and backward pointers of elem to NULL.

If the list is circular, the caller should ensure that the forward and backward pointers of the first element are initialized to point to that element, and the prev argument of the insque() call should also point to the element.

The remque() function removes the element pointed to by elem from the doubly-linked list.  

CONFORMING TO

POSIX.1-2001.  

NOTES

Traditionally (e.g., SunOS, Linux libc4 and libc5), the arguments of these functions were of type struct qelem *, defined as:

struct qelem {
    struct qelem *q_forw;
    struct qelem *q_back;
    char          q_data[1];
};

This is still what you will get if _GNU_SOURCE is defined before including <search.h>.

The location of the prototypes for these functions differs among several versions of UNIX. The above is the POSIX version. Some systems place them in <string.h>.  

BUGS

In glibc 2.4 and earlier, it was not possible to specify prev as NULL. Consequently, to build a linear list, the caller had to build a list using an initial call that contained the first two elements of the list, with the forward and backward pointers in each element suitably initialized.  

EXAMPLE

The program below demonstrates the use of insque(). Here is an example run of the program:

$ ./a.out -c a b c
Traversing completed list:
    a
    b
    c
That was a circular list
 

Program source

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <search.h>

struct element {
    struct element *forward;
    struct element *backward;
    char *name;
};

static struct element *
new_element(void)
{
    struct element *e;

    e = malloc(sizeof(struct element));
    if (e == NULL) {
        fprintf(stderr, "malloc() failed\n");
        exit(EXIT_FAILURE);
    }

    return e;
}

int
main(int argc, char *argv[])
{
    struct element *first, *elem, *prev;
    int circular, opt, errfnd;

    /* The "-c" command-line option can be used to specify that the
       list is circular */

    errfnd = 0;
    circular = 0;
    while ((opt = getopt(argc, argv, "c")) != -1) {
        switch (opt) {
        case 'c':
            circular = 1;
            break;
        default:
            errfnd = 1;
            break;
        }
    }

    if (errfnd || optind >= argc) {
        fprintf(stderr,  "Usage: %s [-c] string...\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    /* Create first element and place it in the linked list */

    elem = new_element();
    first = elem;

    elem->name = argv[optind];

    if (circular) {
        elem->forward = elem;
        elem->backward = elem;
        insque(elem, elem);
    } else {
        insque(elem, NULL);
    }

    /* Add remaining command-line arguments as list elements */

    while (++optind < argc) {
        prev = elem;

        elem = new_element();
        elem->name = argv[optind];
        insque(elem, prev);
    }

    /* Traverse the list from the start, printing element names */

    printf("Traversing completed list:\n");
    elem = first;
    do {
        printf("    %s\n", elem->name);
        elem = elem->forward;
    } while (elem != NULL && elem != first);

    if (elem == first)
        printf("That was a circular list\n");

    exit(EXIT_SUCCESS);
}
 

COLOPHON

This page is part of release 3.81 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
CONFORMING TO
NOTES
BUGS
EXAMPLE
Program source
COLOPHON


Please read "Why adblockers are bad".



Other free services
toURL.org
Shorten long
URLs to short
links like
http://tourl.org/2
tourl.org
.
Reverse DNS lookup
Find out which hostname(s)
resolve to a
given IP or other hostnames for the server
www.reversednslookup.org
rdf newsfeed | rss newsfeed | Atom newsfeed
- Powered by LeopardCMS - Running on Gentoo -
Copyright 2004-2013 Sascha Nitsch Unternehmensberatung UG(haftungsbeschränkt)
Valid XHTML1.1 : Valid CSS : buttonmaker
- Level Triple-A Conformance to Web Content Accessibility Guidelines 1.0 -
- Copyright and legal notices -
Time to create this page: 3.2 ms