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getprotobyname(3c)
Standard C Library Functions getprotobyname(3C)
NAME
getprotobyname, getprotobyname_r, getprotobynumber, getprotobynumber_r,
getprotoent, getprotoent_r, setprotoent, endprotoent - get protocol
entry
SYNOPSIS
#include <netdb.h>
struct protoent *getprotobyname(const char *name);
struct protoent *getprotobyname_r(const char *name,
struct protoent *result, char *buffer,
int buflen);
struct protoent *getprotobynumber(int proto);
struct protoent *getprotobynumber_r(int proto, struct protoent *result,
char *buffer, int buflen);
struct protoent *getprotoent(void);
struct protoent *getprotoent_r(struct protoent *result, char *buffer,
int buflen);
int setprotoent(int stayopen);
int endprotoent(void);
DESCRIPTION
These functions return a protocol entry. Two types of interfaces are
supported: reentrant (getprotobyname_r(), getprotobynumber_r(), and
getprotoent_r()) and non-reentrant (getprotobyname(), getprotobynum‐
ber(), and getprotoent()). The reentrant functions can be used in sin‐
gle-threaded applications and are safe for multithreaded applications,
making them the preferred interfaces.
The reentrant routines require additional parameters which are used to
return results data. result is a pointer to a struct protoent structure
and will be where the returned results will be stored. buffer is used
as storage space for elements of the returned results. buflen is the
size of buffer and should be large enough to contain all returned data.
buflen must be at least 1024 bytes.
getprotobyname_r(), getprotobynumber_r(), and getprotoent_r() each
return a protocol entry.
The entry may come from one of the following sources: the protocols
file (see protocols(5)), and the NIS maps protocols.byname and proto‐
cols.bynumber. The sources and their lookup order are specified in the
nsswitch.conf(5) configuration.
The getprotobyname_r() and getprotobynumber_r() functions sequentially
search from the beginning of the file until a matching protocol name or
protocol number is found, or until an EOF is encountered.
getprotobyname() and getprotobynumber() have the same functionality as
getprotobyname_r() and getprotobynumber_r() except that a static buffer
is used to store returned results. These functions are Unsafe in a mul‐
tithreaded application.
getprotoent_r() enumerates protocol entries: successive calls to get‐
protoent_r() will return either successive protocol entries or NULL.
Enumeration might not be supported by some sources. If multiple threads
call getprotoent_r(), each will retrieve a subset of the protocol data‐
base.
getprotent() has the same functionality as getprotent_r() except that a
static buffer is used to store returned results. This routine is Unsafe
in a multithreaded application.
setprotoent() "rewinds" to the beginning of the enumeration of protocol
entries. If the stayopen flag is non-zero, resources such as open file
descriptors are not deallocated after each call to getprotobynumber_r()
and getprotobyname_r(). Calls to the getprotobyname_r(), getprotoby‐
name(), getprotobynumber_r(), and getprotobynumber() functions might
leave the enumeration in an indeterminate state, so setprotoent()
should be called before the first call to getprotoent_r() or getpro‐
toent(). The setprotoent() function has process-wide scope, and rewinds
the protocol entries for all threads calling getprotoent_r() as well as
main-thread calls to getprotoent().
The endprotoent() function can be called to indicate that protocol pro‐
cessing is complete; the system may then close any open protocols file,
deallocate storage, and so forth. It is legitimate, but possibly less
efficient, to call more protocol functions after endprotoent().
The internal representation of a protocol entry is a protoent structure
defined in <netdb.h> with the following members:
char *p_name;
char **p_aliases;
int p_proto;
RETURN VALUES
The getprotobyname_r(), getprotobyname(), getprotobynumber_r(), and
getprotobynumber() functions return a pointer to a struct protoent if
they successfully locate the requested entry; otherwise they return
NULL.
The getprotoent_r() and getprotoent() functions return a pointer to a
struct protoent if they successfully enumerate an entry; otherwise they
return NULL, indicating the end of the enumeration.
ERRORS
The getprotobyname_r(), getprotobynumber_r(), and getprotoent_r() func‐
tions will fail if:
ERANGE The length of the buffer supplied by the caller is not large
enough to store the result.
FILES
/etc/protocols
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelSee NOTES below.
SEE ALSO
netdb.h(3HEAD), nsswitch.conf(5), protocols(5), attributes(7)
NOTES
Although getprotobyname_r(), getprotobynumber_r(), and getprotoent_r()
are not mentioned by POSIX 1003.1:2001, they were added to complete the
functionality provided by similar thread-safe functions.
The getprotobyname_r(), getprotobynumber_r(), and getprotoent_r() func‐
tions are reentrant and multithread safe. The reentrant interfaces can
be used in single-threaded as well as multithreaded applications and
are therefore the preferred interfaces.
The getprotobyname(), getprotobyaddr(), and getprotoent() functions use
static storage, so returned data must be copied if it is to be saved.
Because of their use of static storage for returned data, these func‐
tions are not safe for multithreaded applications.
The setprotoent() and endprotoent() functions have process-wide scope,
and are therefore not safe in multi-threaded applications.
Use of getprotoent_r() and getprotoent() is discouraged; enumeration is
well-defined for the protocols file and is supported (albeit ineffi‐
ciently) for NIS, but in general may not be well-defined. The semantics
of enumeration are discussed in nsswitch.conf(5).
BUGS
Only the Internet protocols are currently understood.
HISTORY
The reentrant interfaces getprotobyname_r(), getprotobynumber_r(), and
getprotoent_r() were added to Oracle Solaris in the Solaris 2.3
release.
The getprotobyname(), getprotobynumber(), getprotoent(), setprotoent(),
and endprotoent() functions have been present since the initial release
of Solaris.
Oracle Solaris 11.4 2 Feb 2021 getprotobyname(3C)