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5.8 Unix Extensions

If 'unix is provided (by linking in unix.o), the following functions are defined:

These privileged and symbolic link functions are not in Posix:

— Function: symlink oldname newname

The symlink function makes a symbolic link to oldname named newname.

symlink returns a value of #t if it is successful and #f on failure.

— Function: readlink filename

Returns the value of the symbolic link filename or #f for failure.

— Function: lstat filename

The lstat function is like stat, except that it does not follow symbolic links. If filename is the name of a symbolic link, lstat returns information about the link itself; otherwise, lstat works like stat. See I/O-Extensions.

— Function: nice increment

Increment the priority of the current process by increment. chown returns a value of #t if it is successful and #f on failure.

— Function: acct filename

When called with the name of an exisitng file as argument, accounting is turned on, records for each terminating process are appended to filename as it terminates. An argument of #f causes accounting to be turned off.

acct returns a value of #t if it is successful and #f on failure.

— Function: mknod filename mode dev

The mknod function makes a special file with name filename and modes mode for device number dev.

mknod returns a value of #t if it is successful and #f on failure.

— Function: sync

sync first commits inodes to buffers, and then buffers to disk. sync() only schedules the writes, so it may return before the actual writing is done. The value returned is unspecified.