izabera

asking gemini to write some cube code

i'm writing another lil cube thing. if you've ever written a rubik's cube simulator/solver, you will know that some parts can be more akin to data than to code. one way or another, you always end up with lots and lots of tables to select the right pieces and move them to the right places. if good code reads like poetry and bad code reads like a phonebook, this is always easily in the top 10 most mind-numbingly boring programs of all time.

izabera

namerefs (introduced in bash 4.0) act as aliases for other variables

var=meow
declare -n ref=var

echo $ref  # prints meow

ref=moo
echo $var  # prints moo

izabera

1
/sent/ { stot += sent[s++] = $2 }
/recv/ { rtot += recv[r++] = $2 }
END {
    if (r != s)
        printf "error: s=%d r=%d\n", s, r
    for (i in sent)
        if (sent[i] < recv[i])
            printf "error: sent[%d]=%d recv[%d]=%d\n", i, sent[i], i, recv[i]
    printf "sent=%'d avg=%'d\n", stot, stot/s

izabera

#!/bin/bash

usage () {
    cat << 'eof'
bgcmd manages a long running, interactive command in background

usage:

    bgcmd START command [args...]    # starts a command in background

izabera

# try catch for bash/mksh/zsh/dash/busybox
[ "$BASH_VERSION" ] && shopt -s expand_aliases
alias try='tryblock ()'
alias throw='return'
alias catch='if tryblock; then :; else '
alias end_try='fi'
alias exceptions:='case $? in x) '
alias except=';;'
alias end_exceptions='esac'
alias always=' '

izabera

for the latest chapter of what's becoming a blog on the most cursed bash you can imagine, let's do some maths together

euclid's algorithm for gcd could be written like this in python:

>>> def gcd(a, b):
...     if b:
...         return gcd(b, a%b)
... return a

izabera

you know ${var?error message here} in sh? it produces an error and prints the message if $var is undefined. otherwise it expands to $var

introducing: ${var+${error message here}}

if $var is defined, the spaces in the error message cause a syntax error, which prints the message. otherwise it expands to nothing

(and similarly for all other outer expansions)

it reliably[^reliable] works[^works] perfectly[^dashzsh] in every[^shells] posix sh[^ext]

izabera

A funky shell thingy that I've never seen before

So you're in posix sh and you want to do the equivalent of this in bash:

foo | tee >(bar) >(baz) >/dev/null

(Suppose that bar and baz don't produce output. Add redirections where needed if that's not the case.)

izabera

#if 0
#define _XOPEN_SOURCE 700
#include <aio.h>
#include <arpa/inet.h>
#include <assert.h>
#include <_Complex.h>
#include <ctype.h>
#include <dirent.h>
#include <dlfcn.h>
#include <errno.h>

izabera

This is the table from man 5 terminfo.

Do NOT hardcode terminal escape sequences. Use tput with the cap-names from the table below to get the right code for your terminal.

(P)	indicates that padding may be specified