50

How can I hide the screen output (printf) of a shell application in Linux?

75

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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  • The first one didn't work for wget – Jader Dias Jul 17 '09 at 3:07
  • That's cause wget uses stderr for some of it's output. The second one should work. – theotherreceive Jul 17 '09 at 3:08
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    Incidentally, 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 – Matt Simmons Jul 17 '09 at 3:17
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    For wget you can use the -q options to make it quiet. – pkhamre Mar 30 '12 at 10:12
  • Any way to suppress output written directly to /dev/tty? – d11wtq Jul 17 '14 at 7:08
31

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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  • Can somebody explain how the command > file.log 2>&1 works? – Cory Klein May 23 '11 at 22:37
  • How low of a level would you like to know? – Matt Simmons May 29 '11 at 13:54
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    @nomoreink: it's actually 2 commands, one is > file and the second one is 2>&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 with 2> file. – Hubert Kario Nov 27 '12 at 11:39
13

Hide standard output:

./command >/dev/null

Hide standard output and standard error:

./command >/dev/null 2>&1

Hide standard output and standard error and release terminal (run the command in the background):

./command >/dev/null 2>&1 &
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3

If you just want to hide the output (and not save it to a file), you can use:

Edited:

$ command &> /dev/null

| improve this answer | |
  • This will redirect the output to a file called null – theotherreceive Jul 17 '09 at 3:03
  • It generated a null file – Jader Dias Jul 17 '09 at 3:04
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    you wouldn't have meant /dev/null, would you? – Babu Jul 17 '09 at 3:09
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    Yes, I would have, Babu. I meant $ command &> /dev/null. My apologies for typing too fast for my own good. – Lucho Jul 17 '09 at 3:13
2

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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  • My default stty under Debian/Arch does not have these options. – hendry Mar 3 '12 at 4:46
  • I should of course have mentioned that i wasn't even on the OP's OS. Edited my post. – vike Mar 30 '12 at 10:09

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