Understanding Tilde Expansion in Bash and Zsh

A user reported an issue while using the nono agent sandboxing tool, which displayed a warning regarding PATH entries that the sandbox can write to, specifically ~/.local/bin/. The user explained that when modifying the ~/.bashrc or ~/.zshrc files, the tilde (~) does not expand to the home path ($HOME) in quoted inputs. According to Bash documentation, tilde expansion occurs only when a word begins with an unquoted tilde character. Bash checks for unquoted tilde-prefixes immediately following a colon (:) or the first equals sign (=) and performs tilde expansion in these cases. As a result, instead of adding /home/<user>/.local/bin/ to the PATH, the entry ./~/.local/bin/ is added. The user noted that while the command export PATH=$PATH:~/.local/bin works in Bash and Zsh, it is fragile, as any whitespace can disrupt the variable assignment. The user provided a method to check for this issue and suggested replacing the tilde with $HOME in configuration files. They also acknowledged the nono tool for its warning, suggesting that it could be more detailed.