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#!/usr/bin/env bash - Use bash found in the environment path. Protects against not knowing where user's bash is installed.

set options

set options -xeuo

Commonly used options:

  • -x: turns on debug output, logging each command as it is executed
  • -e: causes the script to exit on most command failures (non-zero exit codes)
  • -u: treats unset variables and parameters other than the special parameters @ or * as an error when performing parameter expansion
  • -o pipefail: causes the script to exit if a command in a pipeline fails
  • use a + to unset them if necessary

Many more options available: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Variables

  • $@ - All of the arguments as individual strings
  • “$*” - All of the arguments as a single string
  • $# - The number of arguments
  • $1..n - Where n is an integer, the nth argument in the list
  • $0 - The command name
  • $? - The last exit code
  • $IFS - Internal/input field separator (defaults to combo of space, newline and tab)

Functions

Declaring a function (needs to happen before use):

function <function_name> { … do things … }

- or -

<function_name>() { … do things … }

  • Nothing ever goes inside parentheses.
  • Passed parameters can be accessed with $1..$n.

Tips

bash.txt · Last modified: 2020/08/12 19:07 by shawn