Shell / Bash

Resources¶

Shells:

Bash
Qshell

POSIX:

Documentation¶

Bash

Cheatsheets¶

Bash scripting cheatsheet

Tutorials¶

Introductions

TBD

Games

Terminus

Introduction¶

Shell¶

Shell (computing) - Wikipedia
- An operating system shell is a computer program that provides relatively broad and direct access to the system on which it runs.
- Most operating system shells are not direct interfaces to the underlying kernel... Shells are special applications that use the kernel API in just the same way as it is used by other application programs.
- Related: Kernel • Operating system • Unix shell
Command-line interface - Wikipedia
- Related: Graphical user interface
Shell script - Wikipedia
- Related: Scripting language

Different shells¶

Using Bash¶

If you're using zsh, run:

vim ~/.zshrc

or

open ~/.zshrc

Command line interface¶

Customization¶

Language¶

Syntax¶

Variables¶

TBD

Quoting¶

In most cases, you should quote variables to prevent word-splitting and globbing issues.

"${VARIABLE}"

Comments¶

TBD

Pipelines¶

TBD

Compound commands¶

Looping constructs¶

Conditional constructs¶

Utilities¶

TBD

Working with files and directories¶

`ls`¶

ls lists the contents of a directory. ls -l produces outputs like the one below:

-rw-r--r--   1 user  staff   1234 Aug 27 21:10 notes.txt
drwxr-xr-x   5 user  staff    160 Aug 27 20:59 my_folder

File type and permissions (-rw-r--r--, drwxr-xr-x)
- First character: file type
  - - = regular file
  - d = directory
  - l = symbolic link
- Next 9 characters: permissions in 3 groups (owner, group, others).
  - r = read, w = write, x = execute (or directory access).
  - Example: rw- means read/write allowed, no execute.
Link count (1, 5)
- Number of hard links to the file (for directories, this counts subdirectories, including . and ..).
Owner (user)
- The username of the file owner.
Group (staff)
- The group that owns the file.
File size (1234, 160)
- Size in bytes (though for directories this is metadata size, not the total contents).
Last modified date/time (Aug 27 21:10)
- When the file was last changed (content or metadata).
File/directory name (notes.txt, my_folder)
- The actual name of the file or directory.