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getprotoent(3) — Linux manual page

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

getprotoent(3)           Library Functions Manualgetprotoent(3)

NAME top

       getprotoent, getprotobyname, getprotobynumber, setprotoent,       endprotoent - get protocol entry

LIBRARY top

       Standard C library (libc,-lc)

SYNOPSIS top

#include <netdb.h>struct protoent *getprotoent(void);struct protoent *getprotobyname(const char *name);struct protoent *getprotobynumber(intproto);void setprotoent(intstayopen);void endprotoent(void);

DESCRIPTION top

       Thegetprotoent() function reads the next entry from the protocols       database (seeprotocols(5)) and returns aprotoent structure       containing the broken-out fields from the entry.  A connection is       opened to the database if necessary.       Thegetprotobyname() function returns aprotoent structure for the       entry from the database that matches the protocol namename.  A       connection is opened to the database if necessary.       Thegetprotobynumber() function returns aprotoent structure for       the entry from the database that matches the protocol numbernumber.  A connection is opened to the database if necessary.       Thesetprotoent() 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 thegetproto*() functions.       Theendprotoent() function closes the connection to the database.       Theprotoent structure is defined in<netdb.h> as follows:           struct protoent {               char  *p_name;       /* official protocol name */               char **p_aliases;    /* alias list */               int    p_proto;      /* protocol number */           }       The members of theprotoent structure are:p_name The official name of the protocol.p_aliases              A NULL-terminated list of alternative names for the              protocol.p_proto              The protocol number.

RETURN VALUE top

       Thegetprotoent(),getprotobyname(), andgetprotobynumber()       functions return a pointer to a statically allocatedprotoent       structure, or a null pointer if an error occurs or the end of the       file is reached.

FILES top

/etc/protocols              protocol database file

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌────────────────────┬───────────────┬───────────────────────────┐       │Interface│Attribute│Value│       ├────────────────────┼───────────────┼───────────────────────────┤       │getprotoent()      │ Thread safety │ MT-Unsafe race:protoent   │       │                    │               │ race:protoentbuf locale   │       ├────────────────────┼───────────────┼───────────────────────────┤       │getprotobyname()   │ Thread safety │ MT-Unsafe                 │       │                    │               │ race:protobyname locale   │       ├────────────────────┼───────────────┼───────────────────────────┤       │getprotobynumber() │ Thread safety │ MT-Unsafe                 │       │                    │               │ race:protobynumber locale │       ├────────────────────┼───────────────┼───────────────────────────┤       │setprotoent(),     │ Thread safety │ MT-Unsafe race:protoent   │       │endprotoent()      │               │ locale                    │       └────────────────────┴───────────────┴───────────────────────────┘       In the above table,protoent inrace:protoent signifies that if       any of the functionssetprotoent(),getprotoent(), orendprotoent() 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.

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            2025-05-17getprotoent(3)

Pages that refer to this page:getent(1), getsockopt(2), socket(2), getnetent(3), getprotoent_r(3), getservent(3), setnetgrent(3), nsswitch.conf(5), protocols(5), pcap-filter(7), raw(7)