redirect AND print stdout

samel_tvom · 08-02-2005, 06:35 PM

Hello!

I would like to redirect stdout to a file (or pipe it) AND display stdout.

something like
$cat whatever.txt > file.txt magicOperatorForStdout

so that stdout is being "split" or copied so I can use it in many places.

thanks!

ilikejam · 08-02-2005, 07:41 PM

Hi.

Code:

$cat whatever.txt | tee file.txt

Dave

samel_tvom · 08-04-2005, 10:23 AM

thanks! but is there also a way to pipe "one of the stdouts" so that "the real stdout" is being printed, but the other is being piped to grep for instance, and later on redirected to a file?

ilikejam · 08-04-2005, 10:47 AM

I'm sure there's an easier way, but I can't think of it at the moment, however, try this:

Code:

mkfifo greppipe
grep myregexp greppipe > grepout &
cat whatever.txt | tee greppipe
rm greppipe

That should give you the results of the grep in 'grepout' and stdout should be printed to (un-grepped) as well.

Dave

samel_tvom · 08-04-2005, 12:44 PM

thanks! I didn't know about the mkfifo command. pretty sweet =)

ilikejam · 08-04-2005, 09:56 PM

Welcome to the power of UNIX... :)

AngryLlama · 08-04-2005, 10:02 PM

narg, I was going to post about tee, but I realized it was already posted.

BTW, This will write both stdout and stderr to the file allfile.txt

Code:

(cat whatever.txt) 2>&1 | tee log.txt

However, how is there a way to split stderr to one file and stdout to another file. Both must be printed to the screen normally.

AngryLlama · 08-04-2005, 10:36 PM

Nevermind. I finally figured it out:

Code:

(cat whatever.txt | tee log.txt) 3>&1 1>&2 2>&3 | tee err.txt 3>&1 1>&2 2>&3

of course, thats worthless if using cat.. but the idea is the same

eddiebaby1023 · 08-07-2005, 05:30 AM

Quote:

Originally posted by AngryLlama
However, how is there a way to split stderr to one file and stdout to another file. Both must be printed to the screen normally.

Code:

someprog 2>err.log 1>out.log

Neither is printed to the screen.

AngryLlama · 08-09-2005, 05:01 PM

Thanks--

However,

Code:

(someprog | tee log.txt) 3>&1 1>&2 2>&3 | tee err.txt 3>&1 1>&2 2>&3

will seperate stderr and stdout to seperate files while still printing both to the screen.

So, it looks like we have every possible redirect scenerio posted on this thread

amseek · 09-28-2012, 03:50 PM

Quote:

Originally Posted by AngryLlama

So, it looks like we have every possible redirect scenerio posted on this thread

-- which is awesome

thank you

David the H. · 09-30-2012, 08:42 AM

We're happy you're happy, but (as the reply page you had to go through to post it undoubtedly pointed out), please don't reopen old threads unless you have something substantial to add to that discussion.

Speaking of which, I can add something to it. bash now offers process substitution, which can usually be used with tee instead of the old cumbersome redirectors.

Example:

Code:

command 2> >( grep "error" >errorfile ) | tee >( grep "output" >outputfile )

stderr is filtered by the first grep and saved to a file.
stdout is split by tee.
One stream is filtered by the second grep and then to a file,
while the raw data goes to screen.

PS: I could swear I came across an almost identical reopened thread just a month or two ago.

amseek · 10-07-2012, 05:37 PM

Quote:

Originally Posted by David the H.

PS: I could swear I came across an almost identical reopened thread just a month or two ago.

'twasn't me

sorry about the old post thing.. didn't notice it was from 2005! whoops. sorry

thanks for the update though and the page itself of course

-Art