GETPROTOENTR(3) Linux Programmer's Manual GETPROTOENTR(3)

NAME
       getprotoentr,  getprotobynamer,  getprotobynumberr  -  get  protocol
       entry (reentrant)

SYNOPSIS
       #include 

       int getprotoentr(struct protoent *resultbuf, char *buf,
                       sizet buflen, struct protoent **result);

       int getprotobynamer(const char *name,
                       struct protoent *resultbuf, char *buf,
                       sizet buflen, struct protoent **result);

       int getprotobynumberr(int proto,
                       struct protoent *resultbuf, char *buf,
                       sizet buflen, struct protoent **result);

   Feature Test Macro Requirements for glibc (see featuretestmacros(7)):

       getprotoentr(), getprotobynamer(), getprotobynumberr():
           BSDSOURCE || SVIDSOURCE

DESCRIPTION
       The getprotoentr(), getprotobynamer(), and getprotobynumberr() func‐
       tions  are  the reentrant equivalents of, respectively, getprotoent(3),
       getprotobyname(3), and getprotobynumber(3).  They  differ  in  the  way
       that  the  protoent  structure is returned, and in the function calling
       signature and return value.  This manual page describes just  the  dif‐
       ferences from the nonreentrant functions.

       Instead  of  returning  a  pointer  to  a statically allocated protoent
       structure as the function result, these functions  copy  the  structure
       into the location pointed to by resultbuf.

       The  buf  array  is  used  to store the string fields pointed to by the
       returned protoent  structure.   (The  nonreentrant  functions  allocate
       these  strings in static storage.)  The size of this array is specified
       in buflen.  If buf is too small, the call fails with the error  ERANGE,
       and  the  caller  must  try  again  with a larger buffer.  (A buffer of
       length 1024 bytes should be sufficient for most applications.)

       If the function call  successfully  obtains  a  protocol  record,  then
       *result  is  set  pointing  to resultbuf; otherwise, *result is set to
       NULL.

RETURN VALUE
       On success, these functions return 0.  On error, they return one of the
       positive error numbers listed in ERRORS.

       On  error, record not found (getprotobynamer(), getprotobynumberr()),
       or end of input (getprotoentr()) result is set to NULL.

ERRORS
       ENOENT (getprotoentr()) No more records in database.

       ERANGE buf is too small.  Try again with a larger buffer (and increased
              buflen).

CONFORMING TO
       These functions are GNU extensions.  Functions with similar names exist
       on some other systems, though typically with different  calling  signa‐
       tures.

EXAMPLE
       The  program  below  uses  getprotobynamer()  to retrieve the protocol
       record for the protocol named in its first command-line argument.  If a
       second  (integer)  command-line argument is supplied, it is used as the
       initial value for buflen; if getprotobynamer() fails  with  the  error
       ERANGE,  the  program  retries with larger buffer sizes.  The following
       shell session shows a couple of sample runs:

           $ ./a.out tcp 1
           ERANGE! Retrying with larger buffer
           getprotobynamer() returned: 0 (success)  (buflen=78)
           pname=tcp; pproto=6; aliases=TCP
           $ ./a.out xxx 1
           ERANGE! Retrying with larger buffer
           getprotobynamer() returned: 0 (success)  (buflen=100)
           Call failed/record not found

   Program source

       #define GNUSOURCE
       #include 
       #include 
       #include 
       #include 
       #include 
       #include 

       #define MAXBUF 10000

       int
       main(int argc, char *argv[])
       {
           int buflen, erangecnt, s;
           struct protoent resultbuf;
           struct protoent *result;
           char buf[MAXBUF];
           char **p;

           if (argc < 2) {
               printf("Usage: %s proto-name [buflen]\n", argv[0]);
               exit(EXITFAILURE);
           }

           buflen = 1024;
           if (argc > 2)
               buflen = atoi(argv[2]);

           if (buflen > MAXBUF) {
               printf("Exceeded buffer limit (%d)\n", MAXBUF);
               exit(EXITFAILURE);
           }

           erangecnt = 0;
           do {
               s = getprotobynamer(argv[1], &resultbuf,
                            buf, buflen, &result);
               if (s == ERANGE) {
                   if (erangecnt == 0)
                       printf("ERANGE! Retrying with larger buffer\n");
                   erangecnt++;

                   /* Increment a byte at a time so we can see exactly
                      what size buffer was required */

                   buflen++;

                   if (buflen > MAXBUF) {
                       printf("Exceeded buffer limit (%d)\n", MAXBUF);
                       exit(EXITFAILURE);
                   }
               }
           } while (s == ERANGE);

           printf("getprotobynamer() returned: %s  (buflen=%d)\n",
                   (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
                   strerror(s), buflen);

           if (s != 0 || result == NULL) {
               printf("Call failed/record not found\n");
               exit(EXITFAILURE);
           }

           printf("pname=%s; pproto=%d; aliases=",
                       resultbuf.pname, resultbuf.pproto);
           for (p = resultbuf.paliases; *p != NULL; p++)
               printf("%s ", *p);
           printf("\n");

           exit(EXITSUCCESS);
       }

SEE ALSO
       getprotoent(3), protocols(5)

COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2010-09-10                  GETPROTOENTR(3)