bash-libraries

A set of useful Bash libraries

Current libraries

• liblog.bash
• libfs.bash
• libos.bash

Use

Load the desired library on you Bash scripts as follows:

...
. /dev/stdin <<< "$(curl -s https://raw.githubusercontent.com/juan131/bash-libraries/master/lib/liblog.bash)"
...

Bash best practices

Here you can find a series of tips when developing a Bash script:

• Start your scripts with the proper shebang: #!/bin/bash.

• Start each file with a description of its contents.

• Use built-in options set -o OPTION:

  • errexit: make your script exit when a command fails. Add || true to allow a command to fail.
  • nounset: make your script exit when using undeclared variables.
  • pipefail: sets the exit code of a pipeline to that of the rightmost command to exit with a non-zero status, or to zero if all commands of the pipeline exit successfully.
  • xtrace: only for debugging.

• Create a main function for scripts long enough to contain at least one other function.

• Use local when declaring variables, unless there is reason to use declare.

• Use readonly when defining "read only" constants.

• Use :- for variables that could be undeclared.

• Naming conventions:

  • Only use uppercase on constants or when a variable is exported to the environment.
  • Use underscore _ instead of - to separate words. Do not use camelCase.
  • Do not start variable names with special characters or numbers.

• Use . xxx.sh instead of source xxx.sh.

• Use $() over backticks.

• Use ${var} instead of $var when concatenating strings.

• Double quote variables, no naked $ signs.

• Use my_func() { ... } instead of function my_func { ... }.

• Use && and || for simple conditionals.

• Put then;, do;, etc. on the same line.

• Use [[ instead of [.

• Prefer absolute paths.

• Avoiding temporary files. Use process substitution (<()) to transform commands output into sth that can be used as a filename:

  # Note that if any of the wget fails, and the diff succeed, this
  # statement will success regarding of built-in options!
  diff <(wget -O - url1) <(wget -O - url2)

• Warnings and errors should go to STDERR.

• Use bash -x myscript.sh for debugging.

Note: You can use ShellCheck to ensure your bash syntax does not contain any warning/error. Linters will be included on repositories to ensure every commit passes a series of checks.