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