This is sockets/t_getservbyname.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is a supplementary file for Chapter 59.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.


Download sockets/t_getservbyname.c

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Function list (Bold in this list means a function is not static)

/* t_getservbyname.c

   Demonstrate the use of getservbyname() to look up the port number
   corresponding to a given service name. Note that getservbyname() is
   now obsolete; new programs should use getaddrinfo().
#include <netdb.h>
#include "tlpi_hdr.h"
main(int argc, char *argv[])
    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s service [protocol]\n", argv[0]);

    struct servent *s = getservbyname(argv[1], argv[2]);
    if (s == NULL)
        fatal("getservbyname() could not find a matching record");

    printf("Official name: %s\n", s->s_name);
    printf("Aliases:      ");
    for (char **pp = s->s_aliases; *pp != NULL; pp++)
        printf(" %s", *pp);
    printf("Port:          %u\n", ntohs(s->s_port));
    printf("Protocol:      %s\n", s->s_proto);



Download sockets/t_getservbyname.c

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