Beej's Guide to Network Programming Using Internet Sockets

Beej’s Guide to Network Programming Using Internet Sockets 508.8. errnoHolds the error code for the last system callPrototypes#include int errno;DescriptionThis is the variable that holds error information for a lot of system calls. If you’ll recall, thingslike socket() and listen() return -1 on error, and they set the exact value of errno to let youknow specifically which error occurred.The header file errno.h lists a bunch of constant symbolic names for errors, such as EADDRI-NUSE, EPIPE, ECONNREFUSED, etc. Your local man pages will tell you what codes can be returnedas an error, and you can use these at run time to handle different errors in different ways.Or, more commonly, you can call perror() or strerror() to get a human-readable versionof the error.Return ValueThe value of the variable is the latest error to have transpired, which might be the code for“success” if the last action succeeded.Examples = socket(PF_INET, SOCK_STREAM, 0);if (s == -1) {perror("socket"); // or use strerror()}tryagain:if (select(n, &readfds, NULL, NULL) == -1) {// an error has occurred!!}// if we were only interrupted, just restart the select() call:if (errno == EINTR) goto tryagain; // AAAA! goto!!!// otherwise it’s a more serious error:perror("select");exit(1);See Alsoperror(), strerror()