1 .\" peter memishian -- meem@gnu.ai.mit.edu
2 .\" $Id: insque.3,v 1.2 1996/10/30 21:03:39 meem Exp meem $
3 .\" and Copyright (c) 2010, Michael Kerrisk <mtk.manpages@gmail.com>
5 .\" %%%LICENSE_START(VERBATIM)
6 .\" Permission is granted to make and distribute verbatim copies of this
7 .\" manual provided the copyright notice and this permission notice are
8 .\" preserved on all copies.
10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
24 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" References consulted:
28 .\" Linux libc source code (5.4.7)
29 .\" Solaris 2.x, OSF/1, and HP-UX manpages
30 .\" Curry's "UNIX Systems Programming for SVR4" (O'Reilly & Associates 1996)
32 .\" Changed to POSIX, 2003-08-11, aeb+wh
33 .\" mtk, 2010-09-09: Noted glibc 2.4 bug, added info on circular
34 .\" lists, added example program
36 .TH INSQUE 3 2014-08-19 "" "Linux Programmer's Manual"
38 insque, remque \- insert/remove an item from a queue
41 .B #include <search.h>
43 .BI "void insque(void *" elem ", void *" prev );
45 .BI "void remque(void *" elem );
49 Feature Test Macro Requirements for glibc (see
50 .BR feature_test_macros (7)):
57 _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
58 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
66 functions manipulate doubly-linked lists.
67 Each element in the list is a structure of
68 which the first two elements are a forward and a
70 The linked list may be linear (i.e., NULL forward pointer at
71 the end of the list and NULL backward pointer at the start of the list)
76 function inserts the element pointed to by \fIelem\fP
77 immediately after the element pointed to by \fIprev\fP.
79 If the list is linear, then the call
80 .I "insque(elem, NULL)"
81 can be used to insert the initial list element,
82 and the call sets the forward and backward pointers of
86 If the list is circular,
87 the caller should ensure that the forward and backward pointers of the
88 first element are initialized to point to that element,
93 call should also point to the element.
97 function removes the element pointed to by \fIelem\fP from the
102 Traditionally (e.g., SunOS, Linux libc4 and libc5),
103 the arguments of these functions were of type \fIstruct qelem *\fP,
109 struct qelem *q_forw;
110 struct qelem *q_back;
116 This is still what you will get if
119 including \fI<search.h>\fP.
121 The location of the prototypes for these functions differs among several
123 The above is the POSIX version.
124 Some systems place them in \fI<string.h>\fP.
125 .\" Linux libc4 and libc 5 placed them
126 .\" in \fI<stdlib.h>\fP.
128 In glibc 2.4 and earlier, it was not possible to specify
131 Consequently, to build a linear list, the caller had to build a list
132 using an initial call that contained the first two elements of the list,
133 with the forward and backward pointers in each element suitably initialized.
135 The program below demonstrates the use of
137 Here is an example run of the program:
141 .RB "$ " "./a.out -c a b c"
142 Traversing completed list:
146 That was a circular list
158 struct element *forward;
159 struct element *backward;
163 static struct element *
168 e = malloc(sizeof(struct element));
170 fprintf(stderr, "malloc() failed\\n");
178 main(int argc, char *argv[])
180 struct element *first, *elem, *prev;
181 int circular, opt, errfnd;
183 /* The "\-c" command\-line option can be used to specify that the
188 while ((opt = getopt(argc, argv, "c")) != \-1) {
199 if (errfnd || optind >= argc) {
200 fprintf(stderr, "Usage: %s [\-c] string...\\n", argv[0]);
204 /* Create first element and place it in the linked list */
206 elem = new_element();
209 elem\->name = argv[optind];
212 elem\->forward = elem;
213 elem\->backward = elem;
219 /* Add remaining command\-line arguments as list elements */
221 while (++optind < argc) {
224 elem = new_element();
225 elem\->name = argv[optind];
229 /* Traverse the list from the start, printing element names */
231 printf("Traversing completed list:\\n");
234 printf(" %s\\n", elem\->name);
235 elem = elem\->forward;
236 } while (elem != NULL && elem != first);
239 printf("That was a circular list\\n");
245 This page is part of release 3.77 of the Linux
248 A description of the project,
249 information about reporting bugs,
250 and the latest version of this page,
252 \%http://www.kernel.org/doc/man\-pages/.