4 ms·

> 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 d

by nisa 8y ago

> 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.

deleted 8y ago
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thisacctforreal 8y ago
I agree. I've used this page successfully as reference for portable syntax: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html 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).

by nisa 8y ago

deleted 8y ago

[deleted]

thisacctforreal 8y ago

I agree. I've used this page successfully as reference for portable syntax: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html 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).