You're probably linking with libucb and didn't read question 6.18. (Readdir in libucb.so wants you to include sys/dir.h, but many SunOS 4.1.x programs included <dirent.h>, consequently, you're mixing native <dirent.h> struct dirent with libucb readdir(). The symptom of this mixup is that the first two characters of each filename are missing. Make sure you use a native compiler (default /opt/SUNWspro/bin/cc, which may not be in your PATH), and not /usr/ucb/cc.