This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
#include <netdb.h> void endprotoent(void); struct protoent *getprotobyname(const char *name); struct protoent *getprotobynumber(int proto); struct protoent *getprotoent(void); void setprotoent(int stayopen);
These functions shall retrieve information about protocols. This information is considered to be stored in a database that can be accessed sequentially or randomly. The implementation of this database is unspecified.
The setprotoent() function shall open a connection to the database, and set the next entry to the first entry. If the stayopen argument is non-zero, the connection to the network protocol database shall not be closed after each call to getprotoent() (either directly, or indirectly through one of the other getproto*() functions), and the implementation may maintain an open file descriptor for the database.
The getprotobyname() function shall search the database from the beginning and find the first entry for which the protocol name specified by name matches the p_name member, opening and closing a connection to the database as necessary.
The getprotobynumber() function shall search the database from the beginning and find the first entry for which the protocol number specified by proto matches the p_proto member, opening and closing a connection to the database as necessary.
The getprotoent() function shall read the next entry of the database, opening and closing a connection to the database as necessary.
The getprotobyname(), getprotobynumber(), and getprotoent() functions shall each return a pointer to a protoent structure, the members of which shall contain the fields of an entry in the network protocol database.
The endprotoent() function shall close the connection to the database, releasing any open file descriptor.
These functions need not be thread-safe.
Upon successful completion, getprotobyname(), getprotobynumber(), and getprotoent() return a pointer to a protoent structure if the requested entry was found, and a null pointer if the end of the database was reached or the requested entry was not found. Otherwise, a null pointer is returned.
The application shall not modify the structure to which the return value points, nor any storage areas pointed to by pointers within the structure. The returned pointer, and pointers within the structure, might be invalidated or the structure or the storage areas might be overwritten by a subsequent call to getprotobyname(), getprotobynumber(), or getprotoent(). The returned pointer, and pointers within the structure, might also be invalidated if the calling thread is terminated.
No errors are defined.
The following sections are informative.
The Base Definitions volume of POSIX.1-2017, <netdb.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .
endservent(3p), getsockopt(3p), netdb.h(0p), setsockopt(3p).