#ifdef linux

If you run any chroot environments such as schroot, they will generally set your prompt as a reminder that you are actually running within a chroot. For example with schroot, I have: $ schroot -c oneiric (oneiric):~$ echo hello hello (oneiric):~$ exit $ When you're in the chroot, you get the chroot name prepended to the prompt (here " (oneiric) "). But if you play tricks with your prompt variables ( PS1 , PS2 , etc) using maybe the magic bash PROMPT_COMMAND variable, you need to take care. I use screen , tmux , or byobu so need to take twice the amount of care since: I modify my prompt quite extensively I only have 1 window which multiplexes all my terminals (it's easier to make a mistake :) The problem is that if you forget which window you're in, you may end up modifying the wrong environment - installing packages in a minimal chroot rather than in your main (non-chroot) environment, or maybe trashing your live system rather than a throw-away chroot...

This is a useful trick to avoid creating lots of intermediate temporary files when you're trying to compare two files that are almost the same, but which have some fields which are guaranteed to be different. Classic examples of this are two log files that have almost the same data in them, but where every line in these files is prefixed by a pesky timestamp which is different between the two files. bash process substitution (using named pipes) to the rescue! Let's assume we have two files " file1.log " and " file2.log " and the first six space-separated fields comprise a timestamp. To ignore those fields and just diff the log file contents we can do this: $ diff <(cut -d" " -f7- /tmp/file1.log) <(cut -d" " -f7- /tmp/file2.log) But why limit yourself to a textual diff. Go graphical if you prefer: $ meld <(cut -d" " -f7- /tmp/file1.log) <(cut -d" " -f7- /tmp/file2.log) This technique can be employed ...

How do you run multiple commands in bash and calculate the total time taken to run all the commands? Use a list by surrounding the commands with curly braces: time { sleep 2; uptime; true && date; } The tricky bit is remembering to add that last semi-colon - without it, the command will fail to be parsed by bash. Also, the spaces either side of the curly braces are mandatory.