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setaliasent(3) — Linux manual page

setaliasent(3)           Library Functions Manualsetaliasent(3)

NAME        top

       setaliasent, endaliasent, getaliasent, getaliasent_r,       getaliasbyname, getaliasbyname_r - read an alias entry

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#include <aliases.h>void setaliasent(void);void endaliasent(void);struct aliasent *getaliasent(void);int getaliasent_r(size_t size;struct aliasent *restrictresult,charbuffer[restrictsize], size_tsize,struct aliasent **restrictres);struct aliasent *getaliasbyname(const char *name);int getaliasbyname_r(size_t size;const char *restrictname,struct aliasent *restrictresult,charbuffer[restrictsize], size_tsize,struct aliasent **restrictres);

DESCRIPTION        top

       One of the databases available with the Name Service Switch (NSS)       is the aliases database, that contains mail aliases.  (To find out       which databases are supported, trygetent --help.)  Six functions       are provided to access the aliases database.       Thegetaliasent() function returns a pointer to a structure       containing the group information from the aliases database.  The       first time it is called it returns the first entry; thereafter, it       returns successive entries.       Thesetaliasent() function rewinds the file pointer to the       beginning of the aliases database.       Theendaliasent() function closes the aliases database.getaliasent_r() is the reentrant version of the previous function.       The requested structure is stored via the first argument but the       programmer needs to fill the other arguments also.  Not providing       enough space causes the function to fail.       The functiongetaliasbyname() takes the name argument and searches       the aliases database.  The entry is returned as a pointer to astruct aliasent.getaliasbyname_r() is the reentrant version of the previous       function.  The requested structure is stored via the second       argument but the programmer needs to fill the other arguments       also.  Not providing enough space causes the function to fail.       Thestruct aliasent is defined in<aliases.h>:           struct aliasent {               char    *alias_name;             /* alias name */               size_t   alias_members_len;               char   **alias_members;          /* alias name list */               int      alias_local;           };

RETURN VALUE        top

       The functionsgetaliasent_r() andgetaliasbyname_r() return a       nonzero value on error.

FILES        top

       The default alias database is the file/etc/aliases.  This can be       changed in the/etc/nsswitch.conf file.

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌───────────────────────────────┬───────────────┬────────────────┐       │Interface│Attribute│Value│       ├───────────────────────────────┼───────────────┼────────────────┤       │setaliasent(),endaliasent(), │ Thread safety │ MT-Safe locale │       │getaliasent_r(),              │               │                │       │getaliasbyname_r()            │               │                │       ├───────────────────────────────┼───────────────┼────────────────┤       │getaliasent(),                │ Thread safety │ MT-Unsafe      │       │getaliasbyname()              │               │                │       └───────────────────────────────┴───────────────┴────────────────┘

STANDARDS        top

       GNU.

HISTORY        top

       The NeXT system has similar routines:           #include <aliasdb.h>           void alias_setent(void);           void alias_endent(void);           alias_ent *alias_getent(void);           alias_ent *alias_getbyname(char *name);

EXAMPLES        top

       The following example compiles withgcc example.c -o example.  It       will dump all names in the alias database.       #include <aliases.h>       #include <errno.h>       #include <stdio.h>       #include <stdlib.h>       int       main(void)       {           struct aliasent *al;           setaliasent();           for (;;) {               al = getaliasent();               if (al == NULL)                   break;               printf("Name: %s\n", al->alias_name);           }           if (errno) {               perror("reading alias");               exit(EXIT_FAILURE);           }           endaliasent();           exit(EXIT_SUCCESS);       }

SEE ALSO        top

getgrent(3),getpwent(3),getspent(3),aliases(5)

COLOPHON        top

       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            2025-06-28setaliasent(3)

Pages that refer to this page:getent(1), nsswitch.conf(5)

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