## Invocation Methods

#### Invoked as interactive login shell\n(ex: SSH, SU) 1. /etc/profile

a. /etc/profile.d/

2. /etc/bashrc 3. ~/.bash_profile

a. ~/.bashrc

4. ~/.bash_logout (upon logout)

#### Invoked as interactive non-login shell (ex: within X window manager) - ~/.bashrc

#### Invoked non-interactively (ex: scripts) - Defined by BASH_ENV

## Basics

###### `$ echo $PATH` See directories bash looks for scripts in.

## Notes

• User specific functions should go in user\'s .bashrc
• Global functions should be individual files in /etc/profile.d/

## Aliases

###### `$ alias -p` See list of active aliases.

###### `$ alias li=\'ls -li\'` Create alias for li for current shell process only.

###### `$ unalias` For unsetting aliases.

## Environment Variables

### Getting Variable Info

###### `$ env` See list of global variables.

###### `$ printenv` Same as above, but with less available option flags.

###### `$ set` See full list of global and local variables.

###### `$ declare` Another long list of environment variables.

###### `$ printenv HOME` See value for global variable HOME.

###### `$ echo $HOME` Same as above.

###### `$ ls $HOME` Use global variable HOME as part of another command.

### Setting Variables

###### `$ testvar=testvalue` Set value of new local variable \'testvar\'.

###### `$ testvar=\“A String Value\”` Same as above, but for strings.

###### `$ testvar=$testvar:moredata` Append more data to the end of existing variable.

###### `$ testvar=$(other | commands)` Assign variable the result of set of commands.

###### `$ export testvar` Export a local variable to the global environment.

###### `$ unset testvar` Removes variable \'testvar\'.

### Variable Arrays

###### `$ vararray=(one two three four five)` Define multiple values for variable as array.

###### `$ echo ${vararray[2]}` Echo column three from vararray.

###### `$ echo ${vararray[*]}` Echo entire array from vararray.

###### `$ vararray[2]=whatever` Change the value of column three in vararray.

###### `$ unset vararry[2]` Remove column 2 from vararray. Prior col 3 now new col 2.

### Variable Notes

• Get value of variables with `$`, but don\'t use `$` when assigning them.
• Global environment variables can be accessed from any child shells of the parent from which it was defined.
• Local environment variables can only be accessed from the process in which they were defined.
• Export and unset, when used in a child shell, will not affect the parent shell.
• Variable arrays start with an index value of zero, not one.

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