reading from / writing to file : 2 dumb questions

[jbv at souslelogo.com]

Richmond,
Thanks for your reply.
Yes, I perfectly understand what happens, but my point is :
why is it so ? What is the logic behind ?
Is it specific to LC of is it closely related to the different OSes
on which LC runs ?
Why the fact of closing then reopening a file leads to overwriting
its content ?

Best,
jbv


> On 09/09/14 18:39, jbv at souslelogo.com wrote:
>> Hi list
>>
>> I am trying to improve the speed of a large script including
>> many loops.
>> Could anyone explain why :
>>
>> - question 1 : if a text file contains "toto", after running the
>> following lines
>>     open file tpath
>>     read from file tpath until EOF
>>     write (it & return & "titi") to file tpath
>>     close file tpath
>>
>> the file contains :
>>    totototo
>>    titi
> Because you are doing this:
>
> reading the contents of file tpath
>
> and THEN writing that ('toto') and 'titi' back to the file.
>
> So 'toto' + 'toto' + return + 'titi' is what you end up with.
> ---------------------------------------------------------------
>>
>> and when running these lines
>>     open file tpath
>>     read from file tpath until EOF
>>     close file tpath
>>     open file tpath
>>     write (it & return & "titi") to file tpath
>>     close file tpath
>>
>> the file contains :
>>     toto
>>     titi
>
> Because here you close the file for reading and then open it again.
>
> In the first case your information is appended to the existing file.
>
> In the second case your information overwrites the existing file.
> -----------------------------------------------------------------