Bash parsing commands break when using $$ in command substitution $(...)

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 8
  • bash-4.4.19-7.el8

Issue

When using $$ in a command substitution $(...), bash cannot parse the command and it fails.

Bash ignores the space after $$and reports syntax error.

Same command works fine in earlier versions of bash on earlier RHEL versions.

Resolution

Update to bash-4.4.19-8.el8_0 shipped with Advisory RHBA-2019:2707 or newer.

Root Cause

Previously, having $$ inside command substitution was reported as syntax error . As a consequence, many scripts were broken. A patch has been applied to fix parsing $$ inside command substitution. As a result, $$ now working correctly inside command substitution.

Diagnostic Steps

The following command is used as an example

A=$(awk -v p=$$ '{print $0}' <testfile)

Returns an error from awk as it is run without a space between p=$$ and '{print}'

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