How does the piped program know that it is piped? I would think that all
it knows is that it is outputing to sdtout. Who changes the data in the
pipe? The shell?
Alan
At 01:33 PM 7/26/01 -0700, you wrote:
>On Jul 26, 1:03pm, Gorman, John wrote:
>
>> Here is an example: telnet hostname | tee hostname.log
>>
>> What this does is telnet to host hostname and record the commands
>> and output from that into the currenct directory as the filename
>> hostname.log.
>>
>> By the way, this is an excellent way to record your testing history,
>> or save your actions for someone who wants to follow what you did at
>> a later time.
>
>The problem with using tee for this purpose is that stdout is no
>longer connected to a tty (or even a pseudo-tty). This means that
>some programs will behave quite differently than they would have had
>you not thrown the pipe in.
>
>A better way to capture this kind of output is to use ``script''...
>
> ocotillo:kev$ script
> Script started, file is typescript
> ocotillo:kev$ echo foo
> foo
> ocotillo:kev$ exit
> exit
> Script done, file is typescript
> ocotillo:kev$ cat typescript
> Script started on Thu Jul 26 13:27:14 2001
> ocotillo:kev$ echo foo
> foo
> ocotillo:kev$ exit
> exit
>
> Script done on Thu Jul 26 13:27:24 2001
>
>An example of a program that behaves differently when it's connected
>to a terminal vs a pipe is ``ls''. Try doing just ``ls'' and then
>``ls | cat'' (or even ``ls | tee''). You'll find that that the former
>gives you a listing with multiple columns while the latter gives you
>a listing with a single column.
>
>Kevin
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