file system query

[Prof. Alan Rogers]

>	 UNIX 4.2 allows files to be opened in append mode. I would 
>	 like to know if this is "Atomic Append". 
>
>	 For example, if two programs open the same file in append mode,
>	 and append few blocks to the file then is it true that the blocks
>         will be appended in order (that is first all the blocks of first 
>         program followed by the blocks of the second program, or vice-versa).
   The other day I had two processes appending to the same file by mistake
(BDS4.2).  The first process wrote a few lines, and then these were
overwritten by the the second process.  When both were finished, the output
of the first process had disappeared.