Shell script best practices, from a decade of scripting things

Post by orwin » Thu, Oct 27, 2022, 9:30 PM UTC

AtlasBarfed wrote: post #391

xelxebar wrote: post #182

Hands down, shell scripting is one of my all time favorite languages. It gets tons of hate, e.g. "If you have to write more than 10 lines, then use a real language," but I feel like those assertions are more socially-founded opinions than technically-backed arguments. My basic thesis is that Shell as a programming language---with it's dynamic scope, focus on line-oriented text, and pipelines---is simply a different p…

Hard Disagree. Bash programming: - no standard unit testing - how do you debug except with printlns? Fail. - each line usually takes a minimum of 10 minutes to debug unless you've done bash scripting for... ten years - basic constructs like the arg array are broken once you have special chars and spaces and want to pass those args to other commands. and UNICODE? Ha. - standard library is nil, you're dependent on a ho…

Post by squirt » Thu, Oct 27, 2022, 9:34 PM UTC

kotlin2 wrote: post #250

Spivak wrote: post #246

Earlier quoted context omitted.

I mean they're not that bad. declare -A mydict( [lookma]=initalization ) mydict[foo]=bar echo "${mydict[foo]}" list=() list+=(foo bar baz) echo "${list[0]}"

Now do an associative array containing another associative array.

  declare -A outer=(
    [inner]="_inner"
  )
  declare -A _inner=(
    [key]="value"
  )

  declare -n inner="${outer[inner]}"
  echo "${inner[key]}"
  # value

Post by ahungry » Thu, Oct 27, 2022, 10:03 PM UTC

Post by crucialfelix » Thu, Oct 27, 2022, 10:13 PM UTC

irrational wrote: post #313

snidane wrote: post #204

Earlier quoted context omitted.

Shell and SQL make you 10x productive over any alternative. Nothing even comes close. I've seen people scrambling for 1 hours to write some data munging, then spend another 1 hour to run it through a thread pool to utilize those cores , while somebody comfortable is shell writes a parallelized one liner, rips through GBs of data, and delivers the answer in 15 minutes. What Python is to Java, Shell is to Python. It sp…

> while somebody comfortable is shell writes a parallelized one liner Do you have an example of this? I didn’t even know you could make sql calls in scripts.

  PSQL="psql postgresql://$POSTGRES_USER:$POSTGRES_PASSWORD@$DATABASE_HOST:$DATABASE_PORT/$POSTGRES_DB -t -P pager=off -c "
  
  OLD="CURRENT_DATE - INTERVAL '5 years'"

  $PSQL "SELECT id from apt WHERE apt.created_on > $OLD order by apt.created_on asc;" | while 
  read -r id; do
    if [[ $id != "" ]]; then
      printf "\n\*\* Do something in the loop with id where newer than \"$OLD\" \*\*\*\n"
      # ...
    fi
  done

Post by sophacles » Thu, Oct 27, 2022, 10:21 PM UTC

jayd16 wrote: post #280

xelxebar wrote: post #182

Hands down, shell scripting is one of my all time favorite languages. It gets tons of hate, e.g. "If you have to write more than 10 lines, then use a real language," but I feel like those assertions are more socially-founded opinions than technically-backed arguments. My basic thesis is that Shell as a programming language---with it's dynamic scope, focus on line-oriented text, and pipelines---is simply a different p…

Eh, this is true but I dont think its because of the programming model of bash. I feel like this is conflating the *nix ecosystem with bash. If every programming language was configured by default and had access to standard unix tools with idiomatic bindings, Shell's advantages would be greatly reduced. You still get a scripting language with some neat tricks but I don't think I would reach for it nearly as often if…