bash: how to flush the output from command `tee`

lihao

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Mar 25, 2010, 3:21:06 PM3/25/10

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Below is my pipe line under bash(RHEL5):

/path/to/my_script.sh 2>/dev/null | tee /path/to/log_file

I want to check the output from script '/path/to/my_script.sh'
immediately without having to wait for the buffer to be full. Is there
any bash configuration to handle this and only to this script [not to
the whole bash environment].

BTW. most of the output in the script "/path/to/my_script.sh" are from
the 'echo' command.

Thanks in advance,
lihao

pk

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Mar 25, 2010, 3:17:37 PM3/25/10

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lihao wrote:

Try

man stdbuf

there is an example similar to yours near the end.

Janis Papanagnou

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Mar 25, 2010, 3:31:45 PM3/25/10

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lihao wrote:
> Below is my pipe line under bash(RHEL5):
>
> /path/to/my_script.sh 2>/dev/null | tee /path/to/log_file
>
> I want to check the output from script '/path/to/my_script.sh'
> immediately without having to wait for the buffer to be full. Is there
> any bash configuration to handle this and only to this script [not to
> the whole bash environment].

In bash; not that I know of.

I use a pty. If you like, have a look at the book "Advanced Programming in
the UNIX Environment". The source code of the pty program from the book are
available online. Google for it.

Janis

Sidney Lambe

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Mar 25, 2010, 4:06:22 PM3/25/10

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Maybe you could have those echos in the script also echo to,
say, /dev/pts/4

At the prompt, from /dev/pts/5:

echo -e "\n\nfoo\n" > /dev/pts/4

Output at /dev/pts/4

root:/root:
$

foo

Ctrl-c to exit.

Sid

Sidney Lambe

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Mar 25, 2010, 4:35:10 PM3/25/10

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Wait a second. They are already echoing to whatever pty you
are running the script from. Where else?
I guess I'm not following this and should just shut up.

Sid

Sven Mascheck

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Mar 25, 2010, 7:39:22 PM3/25/10

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lihao wrote:

> /path/to/my_script.sh 2>/dev/null | tee /path/to/log_file
>
> I want to check the output from script '/path/to/my_script.sh'
> immediately without having to wait for the buffer to be full.

> [...] BTW. most of the output in the script "/path/to/my_script.sh"

> are from the 'echo' command.

In that case, sh -c "echo x;sleep 1"|tee, I can't see any block buffering.
Not even with sh -c "echo x|grep .;sleep 1"|tee.
What and how many commands in your script are fully buffered?

foo

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Jul 30, 2010, 11:32:51 AM7/30/10

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... | tee /dev/stderr | tee /path/to/log_file ?

Janis Papanagnou

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Jul 30, 2010, 12:23:33 PM7/30/10

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On 30/07/10 17:32, foo wrote:
> ... | tee /dev/stderr | tee /path/to/log_file ?
>
>

pty

Icarus Sparry

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Jul 30, 2010, 12:54:56 PM7/30/10

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pty is very very good.

A simpler answer in this case might be multitee.

... | multitee 0-1,2,3 3>/path/to/log_file

It might even be the case that the OP's 'tee' command would work

... | tee /dev/stderr /path/to/log_file

(I am guessing that the OP would be actually running
... | tee /dev/stderr | tee /path/to/log_file | something
as otherwise they will be getting two copies of the output of ..., one on
stderr and one on stdout)

bardy

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Jul 31, 2010, 11:00:17 AM7/31/10

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Or simply:

cmd 2>/dev/null | tee /dev/stderr > file.log