endservent, getservbyname, getservbyport, getservent, setservent — network services database functions
#include <netdb.h>
void endservent(void);
struct servent *getservbyname(const char *name, const char *proto);
struct servent *getservbyport(int port, const char *proto);
struct servent *getservent(void);
void setservent(int stayopen);
These functions shall retrieve information about network services. 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 setservent() 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 net database shall not be closed after each call to the getservent() function (either directly, or indirectly through one of the other getserv*() functions), and the implementation may maintain an open file descriptor for the database. If a file descriptor is used, the FD_CLOEXEC flag shall be set; see <fcntl.h>.
The getservent() function shall read the next entry of the database, opening and closing a connection to the database as necessary.
The getservbyname() function shall search the database from the beginning and find the first entry for which the service name specified by name matches the s_name member and the protocol name specified by proto matches the s_proto member, opening and closing a connection to the database as necessary. If proto is a null pointer, any value of the s_proto member shall be matched.
The getservbyport() function shall search the database from the beginning and find the first entry for which the port specified by port matches the s_port member and the protocol name specified by proto matches the s_proto member, opening and closing a connection to the database as necessary. If proto is a null pointer, any value of the s_proto member shall be matched. The port argument shall be a value obtained by converting a uint16_t in network byte order to int.
The getservbyname(), getservbyport(), and getservent() functions shall each return a pointer to a servent structure, the members of which shall contain the fields of an entry in the network services database.
The endservent() function shall close the database, releasing any open file descriptor.
These functions need not be thread-safe.
Upon successful completion, getservbyname(), getservbyport(), and getservent() return a pointer to a servent 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 getservbyname(), getservbyport(), or getservent(). The returned pointer, and pointers within the structure, might also be invalidated if the calling thread is terminated.
The getservbyname(), getservbyport(), getservent(), and setservent() functions may fail if:
- [EMFILE]
- All file descriptors available to the process are currently open.
- [ENFILE]
- The maximum allowable number of files is currently open in the system.
None.
The port argument of getservbyport() need not be compatible with the port values of all address families.
None.
None.
First released in Issue 6. Derived from the XNS, Issue 5.2 specification.
Austin Group Interpretation 1003.1-2001 #156 is applied.
SD5-XBD-ERN-14 is applied.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0088 [75] and XSH/TC1-2008/0089 [75] are applied.
POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0095 [656] is applied.
Austin Group Defect 368 is applied, adding a requirement for FD_CLOEXEC to be set if a file descriptor is used, and adding the [EMFILE] and [ENFILE] errors.
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