4 SC1098

Joachim Ansorg edited this page 2021-11-12 10:47:49 +01:00

Table of Contents

• Quote/escape special characters when using eval, e.g. eval "a=(b)".
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:

Quote/escape special characters when using eval, e.g. eval "a=(b)".

Problematic code:

eval $var=(a b)

Correct code:

eval "$var=(a b)"

Rationale:

Shells differ widely in how they handle unescaped parentheses in eval expressions.

• eval foo=bar is allowed by dash, bash and ksh.
• eval foo=(bar) is allowed by bash and ksh, but not dash.
• eval $var=(bar) is allowed by ksh, but not bash or dash.
• eval foo() ( echo bar; ) is not allowed by any shell.

Since the expression is evaluated as shell script code anyways, it should be passed in as a literal string without relying on special case parsing rules in the target shell. Quote/escape the characters accordingly.

Exceptions:

None.

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