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How Unix programmers at restaurants search menus for their favorite plate

Miguel Mota on December 13, 2018

A Unix programmer heads over to the local diner to get something to eat for lunch. He, or Bob as he prefers, knows better than to manually scan the...

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Ben Tomasik • Dec 13 '18

What sort of monster does cat | grep !?

acidnik • Dec 13 '18

With real life menus with millions of lines, you usually start with head | grep, and then, when you one-liner of 15 lines is complete, you replace head with cat and cross your fingers

Jeshan Giovanni BABOOA • Dec 16 '18

real life menus with millions each? ;)

acidnik • Dec 16 '18

That was my attempt to make a joke

Michael • Dec 13 '18 • Edited

You can almost accomplish this entire task using awk. For example:

awk -F '$' '/shrimp/ {printf "%s- %.2f\n", $1, $NF}' < menu.txt

Christopher McClellan • Dec 14 '18

awk is Turing Complete.
s/almost//

Jesús Gómez • Dec 13 '18

Some people, including me:

reddit.com/r/programming/comments/...

Pulkit Singhania • Dec 13 '18

Grep won't be able to find anything because you are searching for ! Which is not in the menu

Ben Sinclair • Dec 13 '18 • Edited

I've been reading the thread about this on /r/programming (how circular!) and they're mostly (deliberately?) missing the point and trying to optimise it rather than to see it as a demonstration of pipes.

cough

grep -q 'shrimp.*$[0-9]\.' menu.txt && echo "Available" || echo ":("

EDIT: changed \d shortcode for [0-9] so it'll work with BSD and GNU grep.

Comment deleted

Ken Bellows • Dec 14 '18 • Edited

That's what this bit at the end is for:

$[0-9]\.

That bit of the regex will only match on a line that contains a dollar sign ($), a single digit ([0-9]), and a literal dot (\.). So "$2.99" will match, but "$12.99" won't, because there are two digits between the dollar sign and the dot.

Ben Sinclair • Dec 14 '18

Try it.

Ben Sinclair • Dec 14 '18

| rev | cut -d\ -f1 | rev

Jesús Gómez • Dec 13 '18

"test returns an exit status code of 1 if the condition passes or 0 if no match." It is actually backwards: reddit.com/r/programming/comments/...

Peter Hoffmann • Dec 14 '18

Why are you guys alwas using awk for field separation? There ist cut -d" " -f3 that is nice as well

Peter Bertok • Dec 14 '18 • Edited

The equivalent is much more readable with PowerShell:

$shrimp = Get-Content menu.txt | Select-String 'shrimp'
$price = $shrimp | ForEach-Object { $cols = $_ -split ' '; $cols[-1] }
$under10 = [decimal]$price.Substring(1) -lt 10
if ( $under10 ) { 'Available!' } else { ':(' }

Of course, you can use aliases to make this a bit "shorter", but then we're back in the world of Unix, where precious bytes have to be saved to achieve acceptable performance on 300 baud Teletype terminals:

$p = gc menu.txt | sls 'shrimp' | % { $c = $_ -split ' '; $c[-1] }
if ([decimal]$p.Substring(1) -lt 10) {'Available!'} else {':('}

Cat Chenal • Dec 15 '18 • Edited

Given this menu:

ps1$cat menu.txt

the menu

steak burrito $11.95
pasta and shrimp $9.75
caesar salad $6.50
shrimp salad $9.99
alfredo shrimp $10

My Nix programmer does this:

awk -F$ '/shrimp/{if ($NF < 10){ print $1}}' menu.txt

pasta and shrimp
shrimp salad

awk rules!

labibllaca • Aug 21 '19

if you are looking for meals under 10 bucks, as shown in ($NF < 10), why isn't caesar salad($6.50) in the output ?

Agustin Navcevich • Dec 14 '18

This is why two unix programmers will never eat together, because they will start to discuss which is the best way to order the shrimps

Andrew (he/him) • Dec 13 '18

You're blowing up on Reddit

Mohamed Shoukry • Dec 15 '18

Bob should've rounded up. He probably ran off when he remembered he didn't factor taxes in!
Oh & btw, he should've done a case insensitive grep grep -i shrimp menu.txt. Although if he's using awk anyway, then he might have included that there too and avoid all those unnecessary pipes! awk '$0~/shrimp/{print $NF}

ppetermann • Dec 16 '18

In a lot of countries the tax is part of the price

Jeff Prestes • Dec 17 '18

hahaha, it's amazing! Congratulations.

Michael • Dec 13 '18

You need to replace your double quotes with literal single quotes. Here's why.

$ echo "Available!"
bash: !": event not found

$ echo 'Available!'
Available!

GManon • Dec 18 '18

Hilarious!

Swarup Kumar Mahapatra • Dec 13 '18

This article is awesome. It really shows all the possibilities in Linux. I am quite surprised by the comments here where people are trying to correct you. Anyways, good job