Useful Tricks with Null Device

/dev/null is the null device. It is very useful when we want to discard output of any operation or we want truncate a file. This is due to the fact reading/writing to /dev/null has no effect. In the case of reading, it generates end of file right away.

To discard stderr, which has file descriptor 2, we can use the following redirection:

ls -l dir 2>/dev/null

To truncate a file, instead of rm and then touch, we can use:

cat /dev/null > file-to-truncate