Bash substring with pipes and stdin

Question

My goal is to cut the output of a command down to an arbitrary number of characters (let's use 6). I would like to be able to append this command to the end of a pipeline, so it should be able to just use stdin.

echo "1234567890" | your command here 
# desired output: 123456

I checked out awk, and I also noticed bash has a substr command, but both of the solutions I've come up with seem longer than they need to be and I can't shake the feeling I'm missing something easier.

I'll post the two solutions I've found as answers, I welcome any critique as well as new solutions!

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Solution found, thank you to all who answered!

It was close between jcollado and Mithrandir - I will probably end up using both in the future. Mithrandir's answer was an actual substring and is easier to view the result, but jcollado's answer lets me pipe it to the clipboard with no EOL character in the way.

Solution 1

Do you want something like this:

echo "1234567890" | cut -b 1-6

Solution 2

What about using head -c/--bytes?

$ echo t9p8uat4ep | head -c 6
t9p8ua

Solution 3

I had come up with:

echo "1234567890" | ( read h; echo ${h:0:6} )

and

echo "1234567890" | awk '{print substr($0,1,6)}'

But both seemed like I was using a sledgehammer to hit a nail.

Solution 4

This might work for you:

printf "%.6s" 1234567890
123456

View more solutions

Comments

[Nick Knowlson]

Thanks, that's quite nice as well! Actually, even a bit better since it doesn't include an EOL character.

[Nick Knowlson]

The only problem with this is I did want something I could append on to the end of a pipeline, something that was able to just use stdin. I will edit the question to make that clearer.

[Sirex]

is that meant to be | ( read h; echo ${h:0:6} ) in the first example ?

[Nick Knowlson]

Honestly, I can't really remember. I just tried it again now and it works both ways for me in zsh, but in bash only seems to work with parentheses. So I guess maybe it is, thanks! :)