diff --git a/include/unistd.h b/include/unistd.h
index 7662e51..de173dc 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -16,6 +16,12 @@ extern "C" {
 #define SEEK_CUR 1
 #define SEEK_END 2
 
+#if defined(_BSD_SOURCE) && !defined(L_SET)
+#define L_SET
+#define L_INCR
+#define L_XTND
+#endif
+
 #undef NULL
 #ifdef __cplusplus
 #define NULL 0
@@ -47,13 +53,10 @@ ssize_t pread(int, void *, size_t, off_t);
 ssize_t pwrite(int, const void *, size_t, off_t);
 
 int chown(const char *, uid_t, gid_t);
-int fchown(int, uid_t, gid_t);
-int lchown(const char *, uid_t, gid_t);
 int fchownat(int, const char *, uid_t, gid_t, int);
 
 int link(const char *, const char *);
 int linkat(int, const char *, int, const char *, int);
-int symlink(const char *, const char *);
 int symlinkat(const char *, int, const char *);
 ssize_t readlink(const char *, char *, size_t);
 ssize_t readlinkat(int, const char *, char *, size_t);
@@ -61,7 +64,6 @@ int unlink(const char *);
 int unlinkat(int, const char *, int);
 int rmdir(const char *);
 int truncate(const char *, off_t);
-int ftruncate(int, off_t);
 
 #define F_OK 0
 #define R_OK 4
@@ -71,7 +73,6 @@ int access(const char *, int);
 int faccessat(int, const char *, int, int);
 
 int chdir(const char *);
-int fchdir(int);
 char *getcwd(char *, size_t);
 
 unsigned alarm(unsigned);
@@ -101,21 +102,23 @@ int isatty(int);
 pid_t tcgetpgrp(int);
 int tcsetpgrp(int, pid_t);
 
+#if defined(_BSD_SOURCE) && !defined(_POSIX_C_SOURCE) \
+ && !defined(_POSIX_SOURCE) && !defined(_XOPEN_SOURCE) \
+ && !defined(_GNU_SOURCE)
+#define setpgrp setpgid
+int symlink(const char *, const char *);
+#endif
+
 uid_t getuid(void);
 uid_t geteuid(void);
 gid_t getgid(void);
 gid_t getegid(void);
 int getgroups(int, gid_t []);
 int setuid(uid_t);
-int setreuid(uid_t, uid_t);
-int seteuid(uid_t);
 int setgid(gid_t);
-int setregid(gid_t, gid_t);
-int setegid(gid_t);
 
 char *getlogin(void);
 int getlogin_r(char *, size_t);
-int gethostname(char *, size_t);
 char *ctermid(char *);
 
 int getopt(int, char * const [], const char *);
@@ -138,23 +141,52 @@ pid_t setpgrp(void);
 char *crypt(const char *, const char *);
 void encrypt(char *, int);
 void swab(const void *, void *, ssize_t);
-long gethostid(void);
 int nice(int);
 void sync(void);
 int getdtablesize(void);
 #endif
 
+#if defined(_BSD_SOURCE) || defined(_XOPEN_SOURCE) \
+ || defined(_POSIX_SOURCE) || defined(_GNU_SOURCE)
+
+#if !( (_POSIX_SOURCE - 0) < 200112L )
+int seteuid(uid_t);
+int setegid(gid_t);
+#endif
+
+int ftruncate(int, off_t);
+int sethostname(const char *, size_t);
+#endif
+
+#if defined(_BSD_SOURCE) || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE)
+int setreuid(uid_t, uid_t);
+int setregid(gid_t, gid_t);
+
+int fchown(int, uid_t, gid_t);
+int lchown(const char *, uid_t, gid_t);
+
+int fchdir(int);
+
+pid_t vfork(void);
+int vhangup(void);
+int usleep(unsigned);
+unsigned ualarm(unsigned, unsigned);
+
+long gethostid(void);
+#endif
+
+#if defined(_BSD_SOURCE) || defined(_GNU_SOURCE)
+int gethostname(char *, size_t);
+int chroot(const char *); /* Also old 
+#endif
+
+
 #ifdef _GNU_SOURCE
 int brk(void *);
 void *sbrk(intptr_t);
 pid_t forkall(void);
-pid_t vfork(void);
-int vhangup(void);
-int chroot(const char *);
 int getpagesize(void);
-int sethostname(const char *, size_t);
-int usleep(unsigned);
-unsigned ualarm(unsigned, unsigned);
+
 int setgroups(size_t, const gid_t []);
 int setresuid(uid_t, uid_t, uid_t);
 int setresgid(gid_t, gid_t, gid_t);