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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |STANDARDS |HISTORY |BUGS |EXAMPLES |SEE ALSO |COLOPHON | |
SLIST(3) Library Functions ManualSLIST(3)SLIST_EMPTY, SLIST_ENTRY, SLIST_FIRST, SLIST_FOREACH, SLIST_HEAD, SLIST_HEAD_INITIALIZER, SLIST_INIT, SLIST_INSERT_AFTER, SLIST_INSERT_HEAD, SLIST_NEXT, SLIST_REMOVE, SLIST_REMOVE_HEAD - implementation of a singly linked list
Standard C library (libc,-lc)
#include <sys/queue.h>SLIST_ENTRY(TYPE);SLIST_HEAD(HEADNAME, TYPE);SLIST_HEAD SLIST_HEAD_INITIALIZER(SLIST_HEADhead);void SLIST_INIT(SLIST_HEAD *head);int SLIST_EMPTY(SLIST_HEAD *head);void SLIST_INSERT_HEAD(SLIST_HEAD *head,struct TYPE *elm, SLIST_ENTRYNAME);void SLIST_INSERT_AFTER(struct TYPE *listelm,struct TYPE *elm, SLIST_ENTRYNAME);struct TYPE *SLIST_FIRST(SLIST_HEAD *head);struct TYPE *SLIST_NEXT(struct TYPE *elm, SLIST_ENTRYNAME);SLIST_FOREACH(struct TYPE *var, SLIST_HEAD *head, SLIST_ENTRYNAME);void SLIST_REMOVE(SLIST_HEAD *head, struct TYPE *elm, TYPE,SLIST_ENTRYNAME);void SLIST_REMOVE_HEAD(SLIST_HEAD *head,SLIST_ENTRYNAME);
These macros define and operate on singly linked lists. In the macro definitions,TYPE is the name of a user-defined structure, that must contain a field of typeSLIST_ENTRY, namedNAME. The argumentHEADNAME is the name of a user-defined structure that must be declared using the macroSLIST_HEAD().Creation A singly linked list is headed by a structure defined by theSLIST_HEAD() macro. This structure contains a single pointer to the first element on the list. The elements are singly linked for minimum space and pointer manipulation overhead at the expense of O(n) removal for arbitrary elements. New elements can be added to the list after an existing element or at the head of the list. AnSLIST_HEAD structure is declared as follows: SLIST_HEAD(HEADNAME, TYPE) head; wherestruct HEADNAME is the structure to be defined, andstructTYPE is the type of the elements to be linked into the list. A pointer to the head of the list can later be declared as: struct HEADNAME *headp; (The nameshead andheadp are user selectable.)SLIST_ENTRY() declares a structure that connects the elements in the list.SLIST_HEAD_INITIALIZER() evaluates to an initializer for the listhead.SLIST_INIT() initializes the list referenced byhead.SLIST_EMPTY() evaluates to true if there are no elements in the list.InsertionSLIST_INSERT_HEAD() inserts the new elementelm at the head of the list.SLIST_INSERT_AFTER() inserts the new elementelm after the elementlistelm.TraversalSLIST_FIRST() returns the first element in the list, or NULL if the list is empty.SLIST_NEXT() returns the next element in the list.SLIST_FOREACH() traverses the list referenced byhead in the forward direction, assigning each element in turn tovar.RemovalSLIST_REMOVE() removes the elementelm from the list.SLIST_REMOVE_HEAD() removes the elementelm from the head of the list. For optimum efficiency, elements being removed from the head of the list should explicitly use this macro instead of the genericSLIST_REMOVE().
SLIST_EMPTY() returns nonzero if the list is empty, and zero if the list contains at least one entry.SLIST_FIRST(), andSLIST_NEXT() return a pointer to the first or nextTYPE structure, respectively.SLIST_HEAD_INITIALIZER() returns an initializer that can be assigned to the listhead.
BSD.
4.4BSD.
SLIST_FOREACH() doesn't allowvar to be removed or freed within the loop, as it would interfere with the traversal.SLIST_FOREACH_SAFE(), which is present on the BSDs but is not present in glibc, fixes this limitation by allowingvar to safely be removed from the list and freed from within the loop without interfering with the traversal.
#include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <sys/queue.h> struct entry { int data; SLIST_ENTRY(entry) entries; /* Singly linked list */ }; SLIST_HEAD(slisthead, entry); int main(void) { struct entry *n1, *n2, *n3, *np; struct slisthead head; /* Singly linked list head */ SLIST_INIT(&head); /* Initialize the queue */ n1 = malloc(sizeof(struct entry)); /* Insert at the head */ SLIST_INSERT_HEAD(&head, n1, entries); n2 = malloc(sizeof(struct entry)); /* Insert after */ SLIST_INSERT_AFTER(n1, n2, entries); SLIST_REMOVE(&head, n2, entry, entries);/* Deletion */ free(n2); n3 = SLIST_FIRST(&head); SLIST_REMOVE_HEAD(&head, entries); /* Deletion from the head */ free(n3); for (unsigned int i = 0; i < 5; i++) { n1 = malloc(sizeof(struct entry)); SLIST_INSERT_HEAD(&head, n1, entries); n1->data = i; } /* Forward traversal */ SLIST_FOREACH(np, &head, entries) printf("%i\n", np->data); while (!SLIST_EMPTY(&head)) { /* List deletion */ n1 = SLIST_FIRST(&head); SLIST_REMOVE_HEAD(&head, entries); free(n1); } SLIST_INIT(&head); exit(EXIT_SUCCESS); }insque(3),queue(7)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17SLIST(3)Pages that refer to this page:queue(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |