How to execute certain commands if a file does NOT exist?

Question

I would like to check if a file exists, then if it does not, create it.

Consider an equivalent of the following C code but with shell scripting.

if(!exist) {
    command;
    command;
}
else {
    command;
    command;
}

Answer 1

Checking if a file exists is a very common task. To search for relevant questions, use the search bar (top right). I got lots of results with the terms "bash script file exists"

In any case, you want either the test builtin or its semantic equivalent [ ]:

[ ! -e your_file ] && >your_file

or

test ! -e your_file && >your_file

which will first test that your_file does not (!) exist (-e) and creates it if that's the case.

For more information on the different tests you can run (other than -e), you can type:

help -m test | less