SC2148: Tips depend on target shell and yours is unknown. Add a shebang.
#  the below excludes are (mostly) about bourne shell and style issues
SC2001: See if you can use ${variable//search/replace} instead.
SC2006: Use $(..) instead of legacy `..`.
SC2046: Quote this to prevent word splitting.
SC2086: Double quote to prevent globbing and word splitting.
SC2103: Consider using ( subshell ), 'cd foo||exit', or pushd/popd instead.
SC2129: Consider using { cmd1; cmd2; } >> file instead of individual redirects.