SC2073 – ShellCheck Wiki

Escape `\<` to prevent it redirecting (or switch to `[[ .. ]]`).

Problematic code:

if [ "aardvark" < "zebra" ]
then
  echo "Alphabetical!"
fi

Correct code:

if [ "aardvark" \< "zebra" ]
then
  echo "Alphabetical!"
fi

or optionally in Bash/Ksh:

if [[ "aardvark" < "zebra" ]]
then
  echo "Alphabetical!"
fi

Rationale:

You are using the operator < or > in a [ test expression.

In this context, it will be considered a file redirection operator instead, so [ "aardvark" < "zebra" ] is equivalent to [ "aardvark" ] < ./zebra, which is true if there exists a readable file zebra in the current directory.

If you wanted to compare two strings lexicographically (alphabetically), escape the < or > with a backslash as in the correct example.

If you want to compare two numbers numerically, use -lt or -ge instead.

Exceptions:

None.

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