How can I have variable redirection in a shell script?

Question

If I have a script with the command

echo xx 2>&1 >junk

I get a file with "xx" in it. If I have a script with

R="2>&1 >junk"
echo xx $R

the script prints "xx 2>&1 >junk", instead of creating the file I desire.
How can I have a redirection that is variable? In the case at hand, I either want to do the redirection, or just set the variable to the empty string to do no redirection. But I need to do it for a number of commands, so I would like to do it as a variable.
Note: environment is embedded Linux with an ash shell from busybox.

William Pursell · Accepted Answer · 2012-10-03 03:32:47Z

1

Use eval:

R="2>&1 >junk"
eval echo xx $R

BTW, if you want the stderr of the command redirected to the file, you must reorder the redirections. cmd 2>&1 > file will print stderr to the original stdout, but cmd > file 2>&1 will direct both stderr and stdout to the named file.

answered Oct 3, 2012 at 3:32

William Pursell

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1 Comment

rich Over a year ago

Thank you. Fixed my problem and caught a bug in one swell foop!

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