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• VASST POSIX Shell and Bash Coding Style Guidelines
  • Consider using Bash instead of the POSIX shell
  • File Layout
  • Provide usage/help information
  • Consider providing a machine-readable “Features:” line
  • Prefer getopts for processing command-line arguments
  • Avoid using $0 in usage and version output
  • Use tabs, not spaces
  • The POSIX shell is called /bin/sh, Bash is called /bin/bash
  • Use an empty string for a false value, and ‘1’ for a true one
  • Error messages, warnings, and diagnostic information go to the standard error stream
  • Consider making diagnostic messages conditional on a command-line option or environment variable
  • Use snake_case for both function and variable names
  • Use uppercase names for variables passed to or from other programs
  • Use lowercase names for the program’s own variables
  • Put as much of the logic as possible in functions
  • Avoid global variables if possible
  • Use local variables
  • Always initialize local variables when declaring them
  • ALWAYS, always, ALWAYS double-quote variable expansions!
  • Exception: running another program with more than one variable argument
  • Put quotes around the longest expression possible
  • Use single quotes for strings that do not contain variable interpolations
  • Use the shellcheck tool
  • Use the shell’s errexit and pipefail modes
  • Keep in mind that errexit mode may be disabled in some cases
  • Always test the error modes that the program checks for
  • Use command substitution on a line separate from a variable declaration
  • Use the Programmer’s Toolbox
  • Use the shell’s own constructs
  • Do not be afraid of using temporary files
  • Use find instead of ls
  • Use Bash’s features
  • Use the -e option when passing patterns to grep, sed, etc
  • Use grep’s -q and -x options as appropriate
  • Use text utilities in the optimal way
  • ALWAYS, always, ALWAYS double-quote variable interpolations!
  • Use two dashes as a delimiter between optional and positional arguments
  • Use printf instead of echo, especially for strings starting with a variable
  • Use temporary files (or directories) instead of files with predictable names
  • Do NOT write parsers for complicated input data (JSON, HTML, INI-style files, etc)
  • DO NOT SOURCE INI-STYLE FILES!
  • Pass variables to tools that support that, e.g. awk or jq
  • Use null-terminated strings for communication between programs if possible
  • Use find -exec instead of find | xargs