SC2294 – ShellCheck Wiki

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eval negates the benefit of arrays. Drop eval to preserve whitespace/symbols (or eval as string).

Problematic code:

check() {
  eval "$@" || exit

Correct code:

check() {
  "$@" || exit


ShellCheck found eval used on an array (or equivalently, "$@"). This is problematic because it effectively throws away all boundary information and rebuilds it from shell words.

Let's say you invoke check sed -i '$d' "my file.txt":

eval "$@" will:

  1. Join the elements on spaces: sed -i $d my file.txt
  2. Split the string on shell word boundaries: sed, -i, $d, my file.txt
  3. Perform shell expansions (assuming $d is unset): sed, -i, my, file.txt
  4. Execute the first element as the command and the rest as its arguments, as if running sed -i 'my' 'file.txt'

"$@" will

  1. Execute the first element as the command and the rest as its arguments, as if running sed -i '$d' 'my file.txt'

Note that while "$@" is essentially always better than eval "$@", it's easy to unintentionally introduce a dependency on bad behavior through the shell debugging anti-strategy of "adding quotes until it works":

# Works with problematic example because of double-escaping, fails with correct example
check ls -l "'My File.txt'" 

# Works with correct example the way it was always intended:
check ls -l "My File.txt" 

The correct example is still better, but the function invocation has to be tweaked as well.


If each of the array elements is a carefully escaped shell command or word, use * instead of @ to explicitly join the elements on spaces which is what would happen anyways:

  'rm /tmp/myfile; '
  'echo "Finished on $(date)" > log.txt; '

# Equivalent to `eval "${on_exit[@]}"`, but more explicit
eval "${on_exit[*]}"

# Even better in this case, as it does not require
# semicolons and commands don't interfere:
for cmd in "${on_exit[@]}"
  eval "$cmd"

If you require eval for another part of the command, explicitly transform the array into a series of escaped shell words. This ensures that the array elements will eval back to themselves:

# Assumed to be outside of our control, 
# otherwise we would output this in an array as well:
COMMAND='dialog --menu "Choose file:" 15 40 4'

# Our array:
  1 "My File.txt"
  2 "My Other File.txt"
eval "$COMMAND ${array[*]@Q}"                     # Bash 4+
eval "$COMMAND $(printf "%q " "${array[@]}")"     # Bash 1+

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