#include <netdb.h> struct servent *getservent(void);
The getservent() function reads the next line from the file /etc/services and returns a structure servent containing the broken out fields from the line. The /etc/services file is opened if necessary.
The servent structure is defined in <netdb.h> as follows:
char *s_name; /* official service name */
char **s_aliases; /* alias list */
int s_port; /* port number */
char *s_proto; /* protocol to use */
getservent() returns the servent structure, or a NULL pointer if an error occurs or the end of the file is reached.