Defining a shell script variable on the same line as sourcing another script

Question

I am coming across lines in ksh scripts that declare a variable and source another shell script on the same line. For example: ``` MYVARIABLE="abc" . ~core/script.sh ``` Does this produce behaviour different from declaring them separately? For example: ``` MYVARIABLE="abc" . ~core/script.sh ```

Accepted Answer

In the case of

```
MYVARIABLE="abc" . ~core/script.sh
```

`MYVARIABLE` is only set to `abc` for the duration of the source (`.`) command. So it will be in scope for the code in `~core/script.sh`.

In the case of

```
MYVARIABLE="abc"
. ~core/script.sh
```

it will be set both in the scope of the current shell/script and in the scope of `~core/script.sh`.

Try running the first, then `echo $MYVARIABLE` to see that it's still empty (assuming it started empty). Run the latter, `echo` again, and you'll see that its value is set in the current shell.

Edit:

Note that `MYVARIABLE` is visible in the scope of `~core/script.sh` in both cases here, but only because you are sourcing the script. If you were instead to run an executable (even an executable shell script), rather than source it, the behavior would be different.

```
MYVARIABLE=foo /usr/local/bin/some_executable
```

will have the variable in scope when executed, but

```
MYVARIABLE=foo
/usr/local/bin/some_executable
```

will not have the variable in scope. In order to have it propagate to an executable/subshell, you would have to `export` it:

```
MYVARIABLE=foo
export MYVARIABLE
/use/local/bin/some_executable
```

In Bourne-derived shells newer than ksh (bash, zsh), you can combine the assignment and export:

```
export MYVARIABLE=foo
```

but that doesn't work in ksh; you need two statements.

Defining a shell script variable on the same line as sourcing another script

Solution

Problem