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--- tools:bash:customization [2024/05/19 21:47] – created - external edit 127.0.0.1
+++ tools:bash:customization [2025/01/04 03:40] (current) – Humphrey Boa-Gart
@@ Line 1: / Line 1: @@
-{{wst>tagout}}
 // This article is **Part 6** in a [[tools:bash|series of cheat-sheets]] on the command line shell, **bash**. ([[tools:bash:files archives|Previous Page]]) //
 ====== Bash: Customization Basics ======
-,14,'## Invocation Methods\n\n#### Invoked as interactive login shell\n(ex: SSH, SU)\n1. /etc/profile\n	a. /etc/profile.d/\n2. /etc/bashrc\n3. ~/.bash_profile\n	a. ~/.bashrc\n4. ~/.bash_logout (upon logout)\n\n#### Invoked as interactive non-login shell\n(ex: within X window manager)\n- ~/.bashrc\n\n#### Invoked non-interactively\n(ex: scripts)\n- Defined by BASH_ENV\n\n## Basics\n\n###### `$ echo $PATH`\nSee directories bash looks for scripts in.\n\n## Notes\n\n- User specific functions should go in user\'s .bashrc\n- Global functions should be individual files in /etc/profile.d/\n\n## Aliases\n\n###### `$ alias -p`\nSee list of active aliases.\n\n###### `$ alias li=\'ls -li\'`\nCreate alias for li for current shell process only.\n\n###### `$ unalias`\nFor unsetting aliases.\n\n## Environment Variables\n\n### Getting Variable Info\n\n###### `$ env`\nSee list of global variables.\n\n###### `$ printenv`\nSame as above, but with less available option flags.\n\n###### `$ set`\nSee full list of global and local variables.\n\n###### `$ declare`\nAnother long list of environment variables.\n\n###### `$ printenv HOME`\nSee value for global variable HOME.\n\n###### `$ echo $HOME`\nSame as above.\n\n###### `$ ls $HOME`\nUse global variable HOME as part of another command.\n\n### Setting Variables\n\n###### `$ testvar=testvalue`\nSet value of new local variable \'testvar\'.\n\n###### `$ testvar=\"A String Value\"`\nSame as above, but for strings.\n\n###### `$ testvar=$testvar:moredata`\nAppend more data to the end of existing variable.\n\n###### `$ testvar=$(other | commands)`\nAssign variable the result of set of commands.\n\n###### `$ export testvar`\nExport a local variable to the global environment.\n\n###### `$ unset testvar`\nRemoves variable \'testvar\'.\n\n### Variable Arrays\n\n###### `$ vararray=(one two three four five)`\nDefine multiple values for variable as array.\n\n###### `$ echo ${vararray[2]}`\nEcho column three from vararray.\n\n###### `$ echo ${vararray[*]}`\nEcho entire array from vararray.\n\n###### `$ vararray[2]=whatever`\nChange the value of column three in vararray.\n\n###### `$ unset vararry[2]`\nRemove column 2 from vararray. Prior col 3 now new col 2.\n\n### Variable Notes\n\n- Get value of variables with `$`, but don\'t use `$` when assigning them.\n- Global environment variables can be accessed from any child shells of the parent from which it was defined.\n- Local environment variables can only be accessed from the process in which they were defined.\n- Export and unset, when used in a child shell, will not affect the parent shell.\n- Variable arrays start with an index value of zero, not one.\n\n\n','xhtml'
+The real power of bash is in its potential for limitless customization. When a bash shell is started, it goes down a list of predefined paths, looking for customization files. Depending on your operating system, it is likely that 99% of what you will need to do can be accomplished in **.bash_aliases**, which is located in the top-level of your user directory.
+**.bashrc** and **.bash_profile** will take edits as well, but this is generally not advisable. Some operating systems have things mixed around, but by default most of them will have comments in the headings of these files explaining how they are arranged on your machine.
+===== Invocation Methods =====
+Depending on how bash is invoked and initialized, there are a handful of other places it will look for customizations.
+==== Invoked as interactive login shell ====
+(ex: SSH, SU)
+  - **/etc/profile** //(global configuration)//
+    -  **/etc/profile.d/** //(directory for global configuration modules)//
+  - **/etc/bashrc** //(more global settings)//
+  - **~/.bash_profile** //(user configuration)//
+    - **~/.bashrc** //(more user configuration)//
+    - **~/.bash_aliases** //(user aliases file)//
+  - **~/.bash_logout** //(performed on user logout)//
+==== Invoked as interactive non-login shell ====
+(ex: within X window manager)
+  - **~/.bashrc**
+  - **~/.bash_aliases**
+==== Invoked non-interactively ====
+(ex: scripts)
+  - Defined by ''BASH_ENV''
+===== Aliases =====
+As you start to use bash more often, you will find yourself using specific combinations of commands and flags to accomplish basic tasks. You can drastically cut the amount of typing you will do by setting **aliases**, which are just pseudo-commands that refer to other commands. These are the simplest customizations to make to bash.
+For example, lets look at the ''ls'' command. The default output of ls is very bare-bones, and you have to type something like ''ls -lhAF'' to get a more detailed view. To make it so typing ''ls'' by itself gives you an easy-to-read detail view, add the following line to your **.bash_aliases** file:
+  ls='ls -lhAF --color=auto'
+Aliases do not have to be permanent, either. To set that same alias to only work for the current shell session, you would run:
+  $ alias ls=\'ls -lhAF --color=auto\'
+To unset that alias, you would run:
+  $ unalias ls
+You can also unset all aliases for the current shell session with:
+  $ unalias -a
+To see a list of active aliases, run:
+  $ alias -p
+===== More Simple Tricks =====
+You can set all sorts of things up in your aliases file. The following are just a few tweaks you can make:
+==== Custom Hostnames ====
+You can tweak the prompt, aka the string that appears before $ in your terminal. (Usually something like **[user@host]$**)
+If you want to restyle the prompt, you will need to set it to the **$PS1** variable. Here is one example with custom green and blue color codes, which you can copy/paste to your aliases file and use right away:
+  PS1='\[\033[01;32m\]\u@\h\[\033[00m\] \[\033[01;34m\]\w\[\033[00m\] \[\033[01;32m\]\$\[\033[00m\] '
+Here is a separate <wrap em>red version</wrap> of the same prompt, which you can add to the aliases file for a root user or superuser, so you can more easily tell at a glance when you are in an account with escalated privs:
+  PS1='\[\033[01;31m\]\u@\h\[\033[00m\] \[\033[01;34m\]\w\[\033[00m\] \[\033[01;31m\]\$\[\033[00m\] '
+Be careful setting the **$PS1** variable, as you can very easily make your shell unusable if you set it the wrong way!
+//(See 'ANSI Escape Codes' at the bottom of this page for more color options.)//
+==== Harden umask ====
+By default your **umask** is probably set up to give read access to things that do not need it by default. To make it so all new files/folders you create are chmodded to 600/700, add the following line to your aliases file:
+  umask 0077
+//(See [[tools:bash:users-permissions#umask|Part 4: Users and Permissions]] for more info.)//
+===== Environment Variables =====
+Just as in any programming language, bash uses **variables**. A variable in bash can contain a number, a character, or a string of characters.
+You have no need to declare a variable, as just assigning a value to its reference will create it.
+==== $PATH ====
+The most important variable you will deal with, is the **$PATH** variable, which specifies the directories that bash will look for executable files. (So you can type ''appname'' instead of ''/path/to/appname'' into your shell to run the program.) To figure out where your $PATH is, run:
+  $ echo $PATH
+This will output something like:
+  /home/user/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+This above line shows that bash will look in your personal **~/.local/bin** directory, as well as a list of common locations for globally-accessible binaries. Your system may have other locations appended here as well for things like games, [[tools:flatpak|Flatpak]] or [[tools:flatpak#snap|Snap]].
+To enable bash to run a custom application (such as a freshly downloaded [[tools:appimage|AppImage]] file) without having to type out the whole directory it is located in, you should place the file into your personal **~/.local/bin** directory. Or, you could put a symlink into that directory like so:
+  $ ln -s /path/to/the.appimage ~/.local/bin/commandname
+With ''commandname'' being whatever you want to type out to open that AppImage file in your shell or launcher.
+You could also put the file or symlink in **/usr/local/bin/** or **/usr/bin/** to make it accessible to other users on the system.
+==== Getting Variable Info ====
+See list of global variables:
+  $ env
+Same as above, but with less available option flags:
+  $ printenv
+See full list of global and local variables:
+  $ set
+Another long list of environment variables:
+  $ declare
+See value for global variable HOME:
+  $ printenv HOME
+Same as above:
+  $ echo $HOME
+Use global variable HOME as part of another command:
+  $ ls $HOME
+==== Setting Variables ====
+Set value of new local variable \'testvar\':
+  $ testvar=testvalue
+Same as above, but for strings:
+  $ testvar=\"A String Value\"
+Append more data to the end of existing variable:
+  $ testvar=$testvar:moredata
+Assign variable the result of set of commands:
+  $ testvar=$(other | commands)
+Export a local variable to the global environment:
+  $ export testvar
+Removes variable \'testvar\':
+  $ unset testvar
+==== Variable Arrays ====
+Define multiple values for variable as array:
+  $ vararray=(one two three four five)
+Echo column three from vararray:
+  $ echo ${vararray[2]}
+Echo entire array from vararray:
+  $ echo ${vararray[*]}
+Change the value of column three in vararray:
+  $ vararray[2]=whatever
+Remove column 2 from vararray. Prior col 3 now new col 2:
+  $ unset vararry[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.
+===== ANSI Escape Codes =====
+When you set your custom hostname earlier in this article, you may have noticed the **\033[..m]** or **\033[..;..m]** blocks, which contain a semicolon-separated list of other numbers with an **m**. Those **"m"** numbers are **ANSI Escape Codes** which you can use to tweak the style of bash output. You have a range of codes available:
+==== Color Codes ====
+^ Color         ^ Foreground Code ^ Background Code ^
+| Black         | 30              | 40              |
+| Red           | 31              | 41              |
+| Green         | 32              | 42              |
+| Yellow        | 33              | 43              |
+| Blue          | 34              | 44              |
+| Magenta       | 35              | 45              |
+| Cyan          | 36              | 46              |
+| Light Gray    | 37              | 47              |
+| Gray          | 90              | 100             |
+| Light Red	| 91      	  | 101             |
+| Light Green	| 92      	  | 102             |
+| Light Yellow	| 93      	  | 103             |
+| Light Blue	| 94      	  | 104             |
+| Light Magenta | 95              | 105             |
+| Light Cyan	| 96      	  | 106             |
+| White    	| 97      	  | 107             |
+==== Other Codes ====
+^ Code ^ Description     ^
+| 00   | Reset/Normal    |
+| 01   | Bold text       |
+| 02   | Faint text      |
+| 03   | Italics         |
+| 04   | Underlined text |
+----
+  * Previous Page: [[tools:bash:files-archives|← Managing Files & Archives]]
+  * [[tools:bash|Back to Index]]
+{{wst>cli}}

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