CODEWITHSUNDEEP
bash
Zhro
Zhro

Reputation: 2614

Reading from a file only partially in a clean and performant manner

This is different from other questions such as Bash read from file and store to variables as I don't want to loop over the content for all possible lines.

To limit overhead, I'm calling read twice instead of piping something like head -n2. But to make read work like this, I'm redirecting it to a for loop.

This feels dirty as I'm using a loop from {1..1} and assigning to variable i which is never used. But this has been the simplest approach that I've found.

Is there any way to further minimize this approach to reading variables from a file while keeping overhead low? The best answer uses only bash built-ins and is both as clean and fast as possible.

File to read:

123
456
789

Script:

for i in {1..1}; do
   read -r a
   read -r b
done < file

echo $a
echo $b

Output:

123
456

Upvotes: 1

Views: 47

Answers (1)

rici
rici

Reputation: 241811

I'd do it with a simple { … } block:

{ read -r a; read -r b; } < file

Upvotes: 1

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