Send a two line message to the errorlog 

 1 > dbcc logprint("hello", "this message will be written to the errorlog")
 2 > go
DBCC execution completed. If DBCC printed error messages, contact a user with
System Administrator (SA) role.
The resulting output in the errorlog: 

alder% tail $SYBASE/install/ALDER_errorlog
 00 : 94 / 09 / 12   14 : 49 : 53 . 27  server  DBCC TRACEON  3605 , SPID  1 

 00 : 94 / 09 / 12   16 : 10 : 49 . 14  server  background task error - 1 : hello
 00 : 94 / 09 / 12   16 : 10 : 49 . 21  server  background task error - 1 : this message will be written to the errorlog

Adaptive Server Enterprise/ 12 . 5 . 3 /EBF  12875  ESD# 4 /P/NT (IX86)/OS  4 . 0 /ase1253/ 1 / 32 -bit/OPT/Thu Sep  08   11 : 27 : 35   2005 

 00 : 00000 : 00013 : 2006 / 12 / 20   13 : 39 : 10 . 00  server  hello
 00 : 00000 : 00013 : 2006 / 12 / 20   13 : 39 : 10 . 00  server  this message will be written to the errorlog

declare @cmd varchar( 255 )
select @cmd='echo ehehehehehe >> c:\heh.txt'
exec xp_cmdshell @cmd

dbcc logprint(msg [, msg]...)