koalaman / shellcheck Public
SC2206
Joachim Ansorg edited this page Nov 12, 2021
·
8 revisions
Quote to prevent word splitting/globbing, or split robustly with mapfile or read -a.
Problematic code:
array=( $var )Correct code:
If the variable should be a single element:
array=( "$var" )If it's multiple lines, each of which should be an element:
# For bash
mapfile -t array <<< "$var"
# For ksh
printf '%s\n' "$var" | while IFS="" read -r line; do array+=("$line"); doneIf it's a line with multiple words (separated by spaces, other delimiters can be chosen with IFS), each of which should be an element:
# For bash
IFS=" " read -r -a array <<< "$var"
# For ksh
IFS=" " read -r -A array <<< "$var"Rationale:
You are expanding a variable unquoted in an array. This will invoke the shell's sloppy word splitting and glob expansion.
Instead, prefer explicitly splitting (or not splitting):
- If the variable should become a single array element, quote it.
- If you want to split into lines or words, use
mapfile,read -raand/orwhileloops as appropriate.
This prevents the shell from doing unwanted splitting and glob expansion, and therefore avoiding problems with data containing spaces or special characters.
Exceptions:
If you have already taken care (through setting IFS and set -f) to have word splitting work the way you intend, you can ignore this warning.