Shell is there a way to use pipes to name a variable?

Question

Let's say I have a text file that has three lines. Its called a

1
2
3

Is there a way to make this possible:

$ x='cat a | head -1'

Do you really want to name the variable 1, or do you want to assign the value 1 to a variable named x? — steeldriver, Jan 27 '18 at 04:18
Possible duplicate of Why is using a shell loop to process text considered bad practice? — Wildcard, Jan 27 '18 at 04:23
You can do it, but the answer to "should you do this?" is a definite "no." However, look into command substitution, which is what you're looking for. (And it's a useful tool that has its place...this just isn't it.) — Wildcard, Jan 27 '18 at 04:25
Very few questions are legitimately duplicates of that one, and this isn't one of them. — Michael Homer, Jan 27 '18 at 04:43
This question has nothing to do with shell looops. It is just "how do I do command substitution?". Answer is x=$(cat a | head -1) or, since the cat is unnecessary, x=$(head -1 a) — cas, Jan 27 '18 at 05:04

score 2 · Answer 1 · answered Jan 27 '18 at 05:07

What you're trying to do is called command substitution, which puts the output of a command onto the command-line of another. e.g. to provide arguments for the other command, or to assign the output to a variable.

You almost had the right syntax. You need to use $() around your command. e.g.

x=$(cat a | head -1) or, since the cat is unnecessary, x=$(head -1 a)

backticks (`) can also be used but are considered obsolete, as they have a number of problems (including inability to nest them, and difficulty in distinguishing them from single-quotes).

Shell is there a way to use pipes to name a variable?

1 Answers1