Shell scripting: How to redirect output from within the script itself?

Arodef · 05-19-2006, 07:37 PM

I know I can do standard and error output redirection when I execute a shell script:

Ex: ./myscript.sh &> capture.txt

Would it be possible to add a line to the myscript.sh itself which would redirect the output so if I just type:

./myscript.sh

I would get a file capture.txt? Also, what would the command be from within the script if I wanted the standard output and error output to not only be captured in a file but to also still output to the terminal?

Thanks for any help!

zackarya · 05-19-2006, 07:46 PM

Hi Arodef,
I found this website which I think answers your questions.

http://www.cpqlinux.com/redirect.html

Zackarya

zhangmaike · 05-19-2006, 08:29 PM

To the beginning of your script, add:

Code:

exec &> capture.txt

for example:

Code:

#!/bin/bash

exec &> capture.txt

echo "This will be piped to capture.txt"

That will redirect all output to the file capture.txt.

As for your second question, I don't think it's possible to have stdout and stderr sent to both the terminal and a file using exec. You can do it from the command line easily enough:

./myscript.sh 2>&1 | tee capture.txt

The link which zackarya provided also discusses the tee command.

Arodef · 05-23-2006, 04:21 PM

Thanks for the suggestions. I did some more googling and I think the following should allow you to use exec to capture the stout and sterr to a file and also get terminal output:

Code:

exec &> capture.txt
tail -f capture.txt >/dev/tty7 &

spirit receiver · 05-23-2006, 07:30 PM

This will also do the trick (and give you a little more flexibility):

Code:

#! /bin/bash

TARGET="target-file"

# file descriptor 4 prints to STDOUT and to TARGET
exec 4> >(while read a; do echo $a; echo $a >>$TARGET; done)
# file descriptor 5 remembers STDOUT
exec 5>&1

# now STDOUT is redirected
exec >&4
date

# wer're done
exec >&5
echo "Date sent to fd4."