some bash features aren’t in the POSIX spec

Illustration of a smiling stick figure with curly hair.

Person: here are some examples! These won’t work in POSIX shells like dash and sh.

arrays

POSIX shells only have one array: $@ for arguments

[[ $DIR=/home/*]]

POSIX alternative: match strings with grep

[[ … ]]

POSIX alternative: [ ... ]

diff <(./cmd1) <./cmd2)

this is called “process substitution”, you can use named pipes instead

the local Keyword

in POSIX shells, all variables are global

for ((i=0; i <3; i++))

sh only has for x in … loops, not C-style loops

a. {png, svg}

you’ll have to type a.png a.svg

{1..5}

POSIX alternative:
$(seq 1 5)

$’\n’

POSIX alternative:
$(printf "\n")

${var//search/replace}

POSIX alternative: pipe to sed