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getnetent(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|FILES \|ATTRIBUTES \|STANDARDS \|HISTORY \|SEE ALSO \|COLOPHON

getnetent(3)             Library Functions Manualgetnetent(3)

NAME top

       getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get       network entry

LIBRARY top

       Standard C library (libc,-lc)

SYNOPSIS top

#include <netdb.h>struct netent *getnetent(void);struct netent *getnetbyname(const char *name);struct netent *getnetbyaddr(uint32_tnet, inttype);void setnetent(intstayopen);void endnetent(void);

DESCRIPTION top

       Thegetnetent() function reads the next entry from the networks       database and returns anetent structure containing the broken-out       fields from the entry.  A connection is opened to the database if       necessary.       Thegetnetbyname() function returns anetent structure for the       entry from the database that matches the networkname.       Thegetnetbyaddr() function returns anetent structure for the       entry from the database that matches the network numbernet of       typetype.  Thenet argument must be in host byte order.       Thesetnetent() function opens a connection to the database, and       sets the next entry to the first entry.  Ifstayopen is nonzero,       then the connection to the database will not be closed between       calls to one of thegetnet*() functions.       Theendnetent() function closes the connection to the database.       Thenetent structure is defined in<netdb.h> as follows:           struct netent {               char      *n_name;     /* official network name */               char     **n_aliases;  /* alias list */               int        n_addrtype; /* net address type */               uint32_t   n_net;      /* network number */           }       The members of thenetent structure are:n_name The official name of the network.n_aliases              A NULL-terminated list of alternative names for the              network.n_addrtype              The type of the network number; alwaysAF_INET.n_net  The network number in host byte order.

RETURN VALUE top

       Thegetnetent(),getnetbyname(), andgetnetbyaddr() functions       return a pointer to a statically allocatednetent structure, or a       null pointer if an error occurs or the end of the file is reached.

FILES top

/etc/networks              networks database file

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌────────────────┬───────────────┬───────────────────────────────┐       │Interface│Attribute│Value│       ├────────────────┼───────────────┼───────────────────────────────┤       │getnetent()    │ Thread safety │ MT-Unsafe race:netent         │       │                │               │ race:netentbuf env locale     │       ├────────────────┼───────────────┼───────────────────────────────┤       │getnetbyname() │ Thread safety │ MT-Unsafe race:netbyname env  │       │                │               │ locale                        │       ├────────────────┼───────────────┼───────────────────────────────┤       │getnetbyaddr() │ Thread safety │ MT-Unsafe race:netbyaddr      │       │                │               │ locale                        │       ├────────────────┼───────────────┼───────────────────────────────┤       │setnetent(),   │ Thread safety │ MT-Unsafe race:netent env     │       │endnetent()    │               │ locale                        │       └────────────────┴───────────────┴───────────────────────────────┘       In the above table,netent inrace:netent signifies that if any of       the functionssetnetent(),getnetent(), orendnetent() are used in       parallel in different threads of a program, then data races could       occur.

STANDARDS top

       POSIX.1-2008.

HISTORY top

       POSIX.1-2001, 4.3BSD.       Before glibc 2.2, thenet argument ofgetnetbyaddr() was of typelong.

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            2025-05-17getnetent(3)

Pages that refer to this page:getent(1), getnetent_r(3), getprotoent(3), getservent(3), inet(3), networks(5), nsswitch.conf(5)

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