using tee to output intermediate results to stdout instead of files

I know that to capture a pipeline’s contents at an intermediate stage of processing, we use tee as ls /bin /usr/bin | sort | uniq | tee abc.txt | grep out , but what if i don’t want to redirect the contents after uniq to abc.txt but to screen(through stdout, ofcourse) so that as an end result , i’ll have on screen, the intermediate contents after uniq as well as the contents after grep.

Answers:

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Method 1

sometimes /dev/tty can be used for that…

ls /bin /usr/bin | sort | uniq | tee /dev/tty | grep out | wc

Method 2

ls /bin /usr/bin | sort | uniq | tee /dev/fd/2 | grep out | wc

On a linux system you can use the the /dev/fd/[num] links like named pipes in many cases. This will duplicate stdout to stderr, which, typically, is your terminal screen, but doesn’t need to be.

Method 3

This command worked for me.

ls /bin /usr/bin | sort | uniq | tee /dev/pts/0 | grep out

You could check what is your terminal using the command tty and replace the tee to redirect the output to that terminal.

References

https://stackoverflow.com/a/18025293/1742825

Method 4

How to do it (example):

exec 3>&1; ( ls |( tee >&3 ) >/dev/null ); exec 3>&-

Which will show the ls result and send it to nirvanah.

To grok the key part, 3>&1, you may read I/O Redirection and esp. this example.

In short: >somefileis short for 1>somefile, which in turn means Assign the file handle of somefile to file descriptor 1 (and drop the former value of that descriptor, for the scope of this process).

So, 3>&1 means: Assign the file descriptor 1 (which may but need not be tty) to the (until now unused) file descriptor 3. We’re effectively using &3 as a temporary variable.

Method 5

mkfifo myfifo
cat myfifo& ls /bin /usr/bin | sort | uniq | tee myfifo | grep out

mkfifo creates a FIFO (first in, first out) special file, a.k.a. a named pipe. 
Start an asynchronous cat to read from the fifo, and then run your pipeline,
teeing the intermediate result to the fifo.

This will produce a [1]+ Done cat myfifo message at the end. 
You can suppress that with this magic trick:

(cat myfifo&); ls /bin /usr/bin | sort | uniq | tee myfifo | grep out

For a long term, robust solution, you might want to create a permanent fifo
(e.g., $HOME/myfifo) rather than creating a new one every time. 
But that will fail if you may be running multiple instances of this simultaneously. 
Alternatively,

• Generate a unique name (e.g., with mktemp).
• Create the fifo in a directory that’s guaranteed to be writable (e.g., /tmp).
• Remove the fifo at the end of the command.

Method 6

In the case this is being run from a terminal you could

• start a terminal multiplexer such as tmux or screen
• split your terminal – in tmux Ctrl B"
• in the first window touch abc.txt then tail -f abc.txt
• switch to the second window and run your command. You’ll see the file created by tee update.

Method 7

http://tldp.org/LDP/abs/html/io-redirection.html

cat stuff | 3>&1 tee 3 | xsel -i

Edit: unfortunately, the above ↑ is incorrect.
An earlier answer of

cat stuff  | tee >(cat) | xsel -i

is good though.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0