Linux by ExamplesHow to redirect output to a file as well as display it out

How to redirect output to a file as well as display it out

December 6th, 2007 mysurface Posted in pipeline, python, tee, Text Manipulation | Hits: 364182 | 48 Comments »

To redirect standard output to a file is easy, you just need to use the redirection symbol, for example:

echo "hello world" > test.txt

But what if I want to display it out as well as store into a file?
Answer: tee

echo "hello world" | tee test.txt

Okay it seems very easy, how about append?

To append the standard output to a file, you do this:

echo"hello world" >> test.txt

Append to file and display it out as well?

echo"hello world" | tee -a test.txt

Okay, how about dealing with standard output(stdout) and standard error(stderr)?
There are two different output stream, one is stdout and another one is stderr. Normal print usually goes to stdout and error related message will goes to stderr. Lets make a simple python script to print 1 line to stdout and 1 line to stderr.

#!/usr/bin/env python

import sys

sys.stdout.write("I am stdout\n")
sys.stderr.write("I am stderr\n")

Ok, lets save the python script as sout.py and try to redirect the output to a file.

$ ./sout.py > test.txt
I am stderr

Standard output is redirect to test.txt but stderr is print out.

What if I want stderr to be redirect and display the stdout?

 ./sout.py 2> test.txt

I want both stored into the file.

 ./sout.py 2&> test.txt

At last, I want both display and redirect to a file:

 ./sout.py 2>&1 | tee test.txt

Interesting isn’t it?

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vansii Says:
December 13th, 2007 at 3:12 pm

Wot if I want to redirect same output to two files without displaying it and without using like cat first file n then copy it to second?

Sachin Says:
October 21st, 2008 at 12:48 am

echo “hello” | tee -a

Sachin Says:
October 21st, 2008 at 12:49 am

echo “hello” | tee -a file1 file2
or
echo “hello” | tee -a file1 file2 > /dev/null

Dinke Says:
November 19th, 2008 at 12:23 am

I was looking for a way how to look at some php script output on screen but also to have whole output saved in a file. Your post is exactly what I needed. Great thanks for sharing this with us. :)

Caught in a Web » Izlaz scripta na ekranu i fajlu Says:
November 19th, 2008 at 12:47 am

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JW Says:
April 18th, 2009 at 12:30 pm

Thanks! I spent hours looking for just this!

Seetharam Says:
August 17th, 2009 at 7:12 pm

Very useful to me

Thanks

Tom Says:
October 7th, 2009 at 8:51 pm

Thanks – the redirect stderr/stdout to a file AND console is what I needed. Appreciate the post.

Zeft Says:
December 4th, 2009 at 4:08 pm

Thanx mate !

yoz Says:
January 15th, 2010 at 11:23 am

hi, what if i want out both stdout&stderr to file1 and stderr to file2 ? is it possible to do that?

jaja Says:
February 3rd, 2010 at 8:55 am

Nice post, bravo!

Erin Says:
March 3rd, 2010 at 11:37 pm

Have you ever piped output through firefox to a file? Would use lynx but its an unsupported browser for the webpage I’m trying to copy down.

Keilaron Says:
March 30th, 2010 at 4:13 am

Erin – do you want to save the HTML, or text format the way –dump does it? Or do you want to save a screenshot? I don’t know if Firefox lets you output the page it sees like that. If you did it, let me know.

jagadesh Says:
May 19th, 2010 at 12:08 pm

can i redirect standard output of one command to mail body in python sendmail script

Nikhil Says:
May 20th, 2010 at 8:19 pm

Exactly what I required . Thanks a lot !

Joviano Dias Says:
July 20th, 2010 at 2:03 pm

this is what i needed, redirect output to file and simultaneously print to command line
Thanks!

Joviano Dias Says:
July 20th, 2010 at 2:05 pm

how do i use this in a batch file since i do not have tee?

Joviano Dias Says:
July 20th, 2010 at 2:10 pm

>>how do i use this in a batch file since i do not have tee?
>>./sout.py 2>&1 | tee test.txt

Got it..
TEE for batch files is at http://www.robvanderwoude.com/tee.php

Jan Vodolan Says:
July 28th, 2010 at 8:28 pm

Hello,
# ./script.sh | tee file.log
if [ $? -ne 0]; then
echo “Do something…”
fi

I need print log to console, save it to log AND handle the exit code !
Unfortunatelly, ‘|tee file’ overwrite exit code of my script. So, “do something” part will never happen. Any idea how to solve this ? Many thanks.
W

leyo04 Says:
August 11th, 2010 at 10:34 am

spot on. my requirement to save to file and display at the same time…

Thanks a lot.

Malcolm Faniel Says:
February 9th, 2011 at 1:49 pm

This web page is really a stroll-through for the entire info you wanted about this and didn’t know who to ask. Glimpse here, and you’ll definitely discover it.

Jan Vodolan Says:
February 25th, 2011 at 2:34 pm

I finally solved my previous problem – how to handle exit code.
# ./script.sh | tee file.log
if [ ${PIPESTATUS[0]} -eq 0 ]; then
echo “Do something…”
fi

lceel Says:
August 9th, 2011 at 3:43 am

It also works if you need to capture the output from a telnet session to a file “telnet soandso | tee /anydir/output.txt”. In Unix and Linux, most Terminals don’t have a “Capture” function as they do in that other o/s. This does it.

Neil Says:
September 5th, 2011 at 4:53 am

Thanks, I was wondering how to do this and google sent me to your page.

GM Says:
September 5th, 2011 at 9:18 pm

Hi,

How do I save something in a script file, then get it to display on the screen as displaying the last word in another file?

I can get all words to display on the screen and in a separate file, and I can get the last word to display on the screen and all of them to display in the file, but I cant seem to get them all to display on the screen and only one on the file. I’ve played around with tee and tail…

sort $input | tee outputfile1.txt displays all the words in the file and on the screen

Charan Says:
November 8th, 2011 at 4:07 pm

Hi,
Very useful to me…..:)
Thanks

ipek Says:
November 19th, 2011 at 8:57 pm

how to do it when you want to write your program
I have written a program using fork and pipes that performs 3 commands using 2 pipes but now i want to store it in a file i know it is like this ls | sort | wc > text
but how to to ii using exec?
exec(“wc”,”wc”,”>”,”text”,NULL); this didn’t work

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January 18th, 2012 at 6:30 pm

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Shawn Sharpe Says:
February 17th, 2012 at 10:27 am

Thanks… I remembered there was tee but I also wanted to see the output in the console at the same time.

Reddeiah Says:
April 5th, 2012 at 2:59 am

I am trying to execute C Program

For that I have to give file as input and output should be stored in output.txt file

I am Using the following command

AIQ1 output.txt

Output in output.txt file is

cat output.txt
Program to distinguish input character
Enter any character or Number :
You Entered a Number

But I need output like this

Program to distinguish input character
Enter any character or Number :3

You Entered a Number

Here problem is The input I am giving from file is not storing in output.txt

Please solve my problem

reshma Says:
May 24th, 2012 at 2:03 pm

Hi,
I am new to the linux and i wanted to redirect the unzipped output to an another directory.Can you please tell me what is the command to perform the above mentioned operation.
I tried the following command.
$unzip zippedfile.zip >> newdir
is that correct?
Please reply soon..

Exheon Says:
October 1st, 2012 at 2:15 am

Hi Reshma, to extract for zipped file to a particular directory yo must issue this command

unzip zippedfile.zip -d /path/to/your/directory

what you’re doing up there is unzipping the files contained by “zippedfile.zip” to the current directory and then append the output, (output for this matter is what a program prints in the screen), to a file called newdir.

Yes it actually creates a “newdir” text file if it not exist yet

Michal Says:
December 3rd, 2012 at 4:13 pm

What if I would like to have redirection of stderr to file a, redirection of stdout to file b and display both on the screen?

Pankaj Says:
December 11th, 2012 at 11:50 pm

Hello,
I need a help to redirect below mentioned commands output to my home directory or create a .txt file.How to redirect plz let me know.
below are the commands
w
date
hostname
uname -a
ps -ef |grep -i pmon
netstat -rn
bdf
bdf |wc -l
tail -100 /var/opt/resmon/log/event.log
sar 1 5

urwa shabir Says:
March 12th, 2013 at 5:26 am

thanks a million….just what i was searching

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Jay A Says:
April 8th, 2015 at 3:14 am

This helps to record the output, and error. I need to have the inputs to the script (readline from screen, user input) and record it, for logging/debugging purposes. Is there another command for that?

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