Refactor main() - Add arg.h and fix usage Given slock is suid we don't want to have half-measures in place to parse the arguments in case the code is changed in the future with somebody not paying enough attention. Also, fix the usage string output to be more consistent across the suckless toolbase and make it reflect the manpage entry. - Comments Use proper block comments and add/change them where necessary to help in studying the code. - Error messages Consistently prepend them with "slock:" and fix wording and do a proper cleanup before quitting (XCloseDisplay and free the locks), making the die() semantics consistent with st's. - getpwuid() error reporting Properly present an error message if getpwuid() fails. - fork() error reporting Properly present an error message if fork() fails. If we cannot close the connection within the fork context we abort the operation and report an error. - execvp() error handling If execvp fails, we cannot call die() afterwards as this implies calling exit(). We must use _exit() to prevent the libc from doing now "illegal" cleanup-work.