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Comment by mixedCase | Hacker News Reader

Sometimes you just want some 30-50 lines of piping a few commands and a couple of conditionals.

Python (the language with the most community traction to replace bash for scripts) is a royal pain to use for this without libraries that are present in no default system, and even with those it often ends up being more verbose than it should.

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> Sometimes you just want some 30-50 lines of piping a few commands and a couple of conditionals.

maybe I was not clear - nothing against shell-scripting but doing some weird dancing like in the article is imho useless, also depending on bash is a stupid idea imho.

posix sh + shellcheck is all you need. if you can't solve your problem in posix sh rethink your code / approach and simplify until it will work.

I agree.

I've used this page successfully as reference for portable syntax:

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3...

Some sections on features I use heavily:

- Parameter Expansion (specifically :-, %, %%, #, ##)

- Special Parameters (specifically "$@", $#, $?)

- set --, this lets you set the $1, $2, etc. variables. I use this with "$@" for arrays, primarily for building command strings.

Here's an small shell script demonstrating some of them:

    #!/bin/sh
    
    # err function
    err() { echo "$1" >&2; exit 1; }
    
    # init variables
    unset src
    unset dst
    dry_run=false
    
    # get arguments
    while [ $# -gt 0 ]; do
        case "$1" in
            -d|--dry-run) dry_run=true ;;
            --) shift; break ;;
            -*) err "unknown option: $1" ;;
            *)
                if [ -z "$src" ]; then src="$1"
                elif [ -z "$dst" ]; then dst="$1"
                else err "unexpected argument: $1"
                fi
            ;;
        esac
        shift
    done
    
    # sanity checks
    ## TODO: print usage
    if [ -z "$src" ]; then err "source not specified"; fi
    if [ ! -d "$src" ]; then err "source does not exist"; fi
    if [ ! -r "$src" ]; then err "cannot read source directory"; fi
    
    if [ -z "$dst" ]; then err "destination not specified"; fi
    
    if ! rsync --version >/dev/null 2>&1; then
        err "missing rsync(1)"
    fi
    
    # build rsync command
    set -- rsync -aq "$src" "$dst"
    
    # log command
    echo "copying $src to $dst"
    echo "    $@"
    if ! $dry_run; then
        if "$@"; then
            echo "success"
        else
            # rsync will have printed an error message
            err "rsync exited with error code $?"
        fi
    else
        echo "dry run; not executing"
    fi

Also be sure to read the man page for test (the [ command).

For typical system scripts, ansible is much better than bash. It has all the commands that are missing from Unix and it's not subject to the bash problems mentioned here.

I agree that python is a pain. It's too low level for any task.

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