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From: superpollo on 21 May 2010 09:34
hi.

is it possible to crete a "text file" such that it has a different
content each time it is opened? such as:

<sample>
$ cat text
this is content
$ cat text
this is different
$ cat text
more different content
</sample>

and so on.

bye
From: Bit Twister on 21 May 2010 10:05
On Fri, 21 May 2010 15:34:04 +0200, superpollo wrote:
> hi.
>
> is it possible to crete a "text file" such that it has a different
> content each time it is opened? such as:
>
><sample>
> $ cat text


Only if you write a program and replace cat with your new program.
From: Ben Finney on 21 May 2010 10:25
superpollo <utente(a)esempio.net> writes:

> is it possible to crete a "text file" such that it has a different
> content each time it is opened?

Not as a text file.

Two existing patterns that I can think of:

* Write a program to generate the output. Run that program.

* Write a program to generate the output on a named pipe (see the Linux
man page 'fifo(7)', or any Unix documentation about FIFOs). Run that
program. Read the named pipe when you want the output.

--
\ “The right to search for truth implies also a duty; one must |
`\ not conceal any part of what one has recognized to be true.” |
_o__) —Albert Einstein |
Ben Finney
From: superpollo on 21 May 2010 10:43
Ben Finney ha scritto:
> superpollo <utente(a)esempio.net> writes:
>
>> is it possible to crete a "text file" such that it has a different
>> content each time it is opened?
>
> Not as a text file.
>
> Two existing patterns that I can think of:
>
> * Write a program to generate the output. Run that program.
>
> * Write a program to generate the output on a named pipe (see the Linux
> man page 'fifo(7)', or any Unix documentation about FIFOs). Run that
> program. Read the named pipe when you want the output.
>

ok, i tried this:


$ cat fifo.sh
#!/usr/bin/env bash
[ -p "numbers" ] || mkfifo "numbers"
for i in $(seq 1 1 10)
do
echo $i >> numbers
done
$ ./fifo.sh &
[1] 7946
$ cat numbers
1
2
3
4
5
6
7
8
9
10
[1]+ Done ./fifo.sh
$

but i expecter something like:

$ cat numbers
1
$ cat numbers
2
$ cat numbers
3
....
From: Ed Morton on 21 May 2010 11:15
On 5/21/2010 9:43 AM, superpollo wrote:
> Ben Finney ha scritto:
>> superpollo <utente(a)esempio.net> writes:
>>
>>> is it possible to crete a "text file" such that it has a different
>>> content each time it is opened?
>>
>> Not as a text file.
>>
>> Two existing patterns that I can think of:
>>
>> * Write a program to generate the output. Run that program.
>>
>> * Write a program to generate the output on a named pipe (see the Linux
>> man page 'fifo(7)', or any Unix documentation about FIFOs). Run that
>> program. Read the named pipe when you want the output.
>>
>
> ok, i tried this:
>
>
> $ cat fifo.sh
> #!/usr/bin/env bash
> [ -p "numbers" ] || mkfifo "numbers"
> for i in $(seq 1 1 10)
> do
> echo $i >> numbers
> done
> $ ./fifo.sh &
> [1] 7946
> $ cat numbers
> 1
> 2
> 3
> 4
> 5
> 6
> 7
> 8
> 9
> 10
> [1]+ Done ./fifo.sh
> $
>
> but i expecter something like:
>
> $ cat numbers
> 1
> $ cat numbers
> 2
> $ cat numbers
> 3
> ...

change ">>" to ">"
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