How can I hide the screen output (printf) of a shell application in Linux?
5 Answers
You can redirect the output of any program so that it won't be seen.
$ program > /dev/null
This will redirect the standard output - you'll still see any errors
$ program &> /dev/null
This will redirect all output, including errors.
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That's cause wget uses stderr for some of it's output. The second one should work. Jul 17, 2009 at 3:08
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2Incidentally, you might want to save that wget output to a log file, so when/if your download stops working, you can figure out why. If it's in a script anyway. If this is a one-off type run, then yea, to the trash Jul 17, 2009 at 3:17
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There are three I/O devices available on the command line.
standard input - 0
standard output - 1
standard error - 2
To redirect standard output (the default output) to a file (and overwrite the file), use
command > file.log
To append to file.log, use two >
s
command >> file.log
To redirect standard error to the file.log, use
command 2> file.log
And to append
command 2>> file.log
To combine the outputs into one stream and send them all to one place
command > file.log 2>&1
This sends 2 (standard error) into 1 (standard output), and sends standard output to file.log
Notice that it's also possible to redirect standard input into a command that expects standard input
command << file.txt
For more details, check out the Advanced Bash Scripting Guide.
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4@nomoreink: it's actually 2 commands, one is
> file
and the second one is2>&1
. The first one redirects the standard out to a file. The second one takes 2nd file descriptor and redirects it to first one. You can do the reverse, redirect standard output to standard error using>&2
and then redirect standard error to a file with2> file
. Nov 27, 2012 at 11:39
Hide standard output:
./command >/dev/null
Hide standard and error outputs:
./command >/dev/null 2>&1
Hide standard output and error outputs and release the terminal (run the command in the background):
./command >/dev/null 2>&1 &
If you just want to hide the output (and not save it to a file), you can use:
Edited:
$ command &> /dev/null
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1Yes, I would have, Babu. I meant $ command &> /dev/null. My apologies for typing too fast for my own good.– LuchoJul 17, 2009 at 3:13
For Mac OS X v10.6 (Snow Leopard):
If you need to hide the output without letting the program know it by checking the output/error file descriptor, you can try using the following in a shell:
stty flusho; command ;stty -flusho
or if you just want to hide input from the terminal by the way:
stty -echo; command ;stty echo
See stty(1) manual page for more information.
For Linux, all I know is that Ubuntu 10.04 (Lucid Lynx) and some Debian/Arch Linux (commented below - thanks, hendry) doesn't have the flusho
setting (and I can't see anything other appropriate in the man-page). The echo
setting works on the Ubuntu anyway.
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I should of course have mentioned that i wasn't even on the OP's OS. Edited my post.– vikeMar 30, 2012 at 10:09