I have a brand-new file called ./foo, which looks like this:
#!/usr/bin/env bash
echo 'Hello world'
The output of the umask command looks like so:
$ umask -S
u=rwx,g=rx,o=rx
$ umask
022
Yet, when I try to execute the brand-new file (no chmod yet), I get the following:
$ ./foo
zsh: permission denied: ./foo
For what it's worth, I get the same thing when I open a bash shell:
$ bash
The default interactive shell is now zsh.
To update your account to use zsh, please run `chsh -s /bin/zsh`.
For more details, please visit https://support.apple.com/kb/HT208050.
bash-3.2$ ./foo
bash: ./foo: Permission denied
And when I inspect the file's permissions with ls -l, it also appears to not be executable:
$ ls -l foo
-rw-r--r-- 1 richiethomas staff 40 Mar 3 10:11 foo
When I chmod the file, however, it works as expected:
$ chmod +x foo
$ ./foo
Hello world
$ ls -l foo
-rwxr-xr-x 1 richiethomas staff 40 Mar 3 10:11 foo
Using this document as a source, I learned that a umask value of 022 means "Owner has all permissions. Everyone else can read and execute, but not write."
If umask is telling me that a file's creator (i.e. me) should be able to execute the file by default, why am I not in fact able to do so?
The only way I know to make a file executable immediately on creation without using hidden steps (like in a function or script) is to create it by copying another file that is already executable. You could use this to make a base template, then edit the file as needed.
$ echo echo hi > a
$ ./a
-bash: ./a: Permission denied
$ chmod +x a
$ ./a
hi
$ cp a b
$ ./b
hi
...but in general, the default behaviors are always there for a reason. Please think about those reasons before changing them. I'm not saying you shouldn't customize your environment however is needed, just that you should be aware of the possible consequences in the specific context. This might save you a bit of time and a few spoons on a dev sandbox, but don't let it go to a company prod system without really thinking it through.