What does this notation mean in bash?

Question

I am pretty sure this will be a duplicate, because I have seen it sometimes at other places, but I do not remember where and I also (obviously) do not know how it is called.

In an other SO post, there is this piece of code (bash):

obj(){
    . <(sed "s/obj/$1/g" obj.class)
}

What does . < do ? If it has a name, what is it ?

Answer 1

Source . ^[Docs]

Read and execute commands from the filename argument in the current shell context.

source is a synonym for dot/period . in bash, but not in POSIX sh, so for maximum compatibility use the period.

• What's the meaning of a dot before a command in shell?

---

Process Substitution < () ^[Docs]

Process substitution allows a process’s input or output to be referred to using a filename.

• What does "< <(command args)" mean in the shell?

Answer 2

Type this into your terminal:

help .

The function obj takes one argument. It executes sed and replaces all occurrences of obj in the file obj.class with the argument. The result is used as Bash code and gets evaluated by the running Bash instance.