Hey there, let's break down this frustrating error you're hitting—especially when shellcheck isn't picking up anything wrong. Here are some common fixes and checks to try:

• Verify your shebang line and execution method
  A super common culprit is running the script with sh instead of bash. Many systems link sh to a POSIX-compliant shell (like dash) that doesn't support Bash-specific syntax (e.g., array initialization with (), advanced brace expansion, or certain function patterns).

  • Double-check your script's first line: it should be #!/bin/bash, not #!/bin/sh.
  • If you're running the script with sh yourscript.sh, switch to bash yourscript.sh instead—even if the shebang is correct, explicitly calling bash ensures you're using the right shell.

• Check where you're using parentheses
  Shellcheck might assume Bash syntax, but if your script has Bash-only constructs that sh rejects, you'll get this error. Common examples include:

  • Array declarations like my_array=(foo bar baz)
  • Process substitution with <(command) or >(command)
  • Some extended function definitions (though basic func() { ... } works in POSIX sh)
    Go through the line mentioned in the error (if the shell specifies it) and confirm the parentheses are part of a Bash-supported feature.

• Fix hidden formatting issues
  If you edited the script on Windows, it might have CRLF line endings instead of Unix LF endings. This can throw off shell parsing in unexpected ways. Use a tool like dos2unix yourscript.sh to convert the line endings, then try running it again. Also, make sure your parentheses are regular ASCII (/)—not full-width or special characters that look the same but aren't parsed correctly.

• Debug line-by-line
  Use Bash's built-in debugging mode to pinpoint the exact line causing the error. Run:

  bash -x yourscript.sh
  

  This will print each command as it's executed, so you can see exactly where the shell hits the unexpected parenthesis. You can also comment out sections of your script to narrow down the problematic code.

• Check for unexpected variable expansion
  If you're using parentheses inside double quotes with a variable (e.g., "$some_var("), make sure the variable's value doesn't contain characters that break the syntax. For example, if some_var ends with a quote or backslash, it could cause the shell to misinterpret the following parenthesis.

内容的提问来源于stack exchange，提问作者Bobby