Correct Bash and shell script variable capitalization

Question

I run across many shell scripts with variables in all caps, and I\'ve always thought that there is a severe misunderstanding with that. My understanding is that, by convent

Answer 1

Any naming conventions followed consistently will always help. Here are a few helpful tips for shell variable naming:

• Use all caps and underscores for exported variables and constants, especially when they are shared across multiple scripts or processes. Use a common prefix whenever applicable so that related variables stand out and won't clash with Bash internal variables which are all upper case.

  Examples:

  • Exported variables with a common prefix: JOB_HOME JOB_LOG JOB_TEMP JOB_RUN_CONTROL
  • Constants: LOG_DEBUG LOG_INFO LOG_ERROR STATUS_OK STATUS_ERROR STATUS_WARNING

• Use "snake case" (all lowercase and underscores) for all variables that are scoped to a single script or a block.

  Examples: input_file first_value max_amount num_errors

  Use mixed case when local variable has some relationship with an environment variable, like: old_IFS old_HOME

• Use a leading underscore for "private" variables and functions. This is especially relevant if you ever write a shell library where functions within a library file or across files need to share variables, without ever clashing with anything that might be similarly named in the main code.

  Examples: _debug _debug_level _current_log_file

• Avoid camel case. This will minimize the bugs caused by case typos. Remember, shell variables are case sensitive.

  Examples: inputArray thisLooksBAD, numRecordsProcessed, veryInconsistent_style

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See also:

• The Open Group Base Specifications Issue 7 - Environment Variables