1.1 Your First Steps with the Command Line#
Before jumping into the world of Git, you first need to be comfortable with the command line. This section will introduce you to the basic commands that are essential for navigating your computer and managing files. Think of it as learning the alphabet before you start writing sentences.
The Command Line Interface#
The command line is a powerful, text-based tool for interacting with your computer. It allows you to perform tasks, manage files, and run programs by typing commands instead of clicking on icons.
The Prompt#
When you open the command line, you are greeted by the prompt. It typically shows information like your username, the machine’s name (hostname), and your current location (directory). For example:
user@hostname:~$
Let’s break this down:
user: The current logged-in user.hostname: The name of the computer.~: A shortcut for your home directory.$: A standard symbol indicating you are logged in as a regular user. An administrator (or root) user often sees a#symbol.
Where Am I? Finding Your Place#
The first thing you need to know is how to find out where you are in the file system.
To display the full path of your current directory, use the pwd (print working directory) command:
pwd
/home/callaram/tds/msdp-book/home/ch1
This command will print the absolute path from the root of the file system (/) to your current location.
Now that you know where you are, let’s see what’s in there. To list the files and directories in your current location, use the ls (list) command:
ls
Creating and Managing Files#
Now that you can navigate, let’s create and work with files.
To create a new, empty file, use the touch command:
touch notes.txt
To add content to a file, you can use the echo command combined with the > redirection operator.
echo "Hello, Command Line!" > notes.txt
Behind the scenes: Redirection
The > symbol is a redirection operator. It takes the output of the command on its left (in this case, the text “Hello, Command Line!”) and, instead of printing it to the screen, writes it into the file on its right (notes.txt). Be careful: if the file already has content, > will overwrite it completely. To append content, use >>.
To display the content of your new file, use the cat (concatenate) command:
cat notes.txt
Hello, Command Line!
Cleaning Up Your Workspace#
To keep things tidy, you’ll need to know how to delete files and directories.
To remove a file, use the rm (remove) command:
rm notes.txt
To remove an empty directory, you can use rmdir. However, to remove a directory and all the files and subdirectories inside it, you need to use rm with the -r (recursive) option.
Let’s remove the my-test-folder directory we created earlier:
rm -r my-test-folder
Danger: rm is forever
The rm command is powerful and irreversible. There is no “Recycle Bin” or “Trash” on the command line. Once a file is deleted with rm, it’s gone for good. Always double-check which directory you are in (pwd) and what you are deleting before you press Enter. You can add the -i (interactive) flag to prompt for confirmation before each removal.
Getting Help#
Almost every command has a help page that lists its options and how to use them. To see it, you can usually use the --help flag.
ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
Mandatory arguments to long options are mandatory for short options too.
-a, --all do not ignore entries starting with .
-A, --almost-all do not list implied . and ..
--author with -l, print the author of each file
-b, --escape print C-style escapes for nongraphic characters
--block-size=SIZE with -l, scale sizes by SIZE when printing them;
e.g., '--block-size=M'; see SIZE format below
-B, --ignore-backups do not list implied entries ending with ~
-c with -lt: sort by, and show, ctime (time of last
modification of file status information);
with -l: show ctime and sort by name;
otherwise: sort by ctime, newest first
-C list entries by columns
--color[=WHEN] colorize the output; WHEN can be 'always' (default
if omitted), 'auto', or 'never'; more info below
-d, --directory list directories themselves, not their contents
-D, --dired generate output designed for Emacs' dired mode
-f do not sort, enable -aU, disable -ls --color
-F, --classify append indicator (one of */=>@|) to entries
--file-type likewise, except do not append '*'
--format=WORD across -x, commas -m, horizontal -x, long -l,
single-column -1, verbose -l, vertical -C
--full-time like -l --time-style=full-iso
-g like -l, but do not list owner
--group-directories-first
group directories before files;
can be augmented with a --sort option, but any
use of --sort=none (-U) disables grouping
-G, --no-group in a long listing, don't print group names
-h, --human-readable with -l and -s, print sizes like 1K 234M 2G etc.
--si likewise, but use powers of 1000 not 1024
-H, --dereference-command-line
follow symbolic links listed on the command line
--dereference-command-line-symlink-to-dir
follow each command line symbolic link
that points to a directory
--hide=PATTERN do not list implied entries matching shell PATTERN
(overridden by -a or -A)
--hyperlink[=WHEN] hyperlink file names; WHEN can be 'always'
(default if omitted), 'auto', or 'never'
--indicator-style=WORD append indicator with style WORD to entry names:
none (default), slash (-p),
file-type (--file-type), classify (-F)
-i, --inode print the index number of each file
-I, --ignore=PATTERN do not list implied entries matching shell PATTERN
-k, --kibibytes default to 1024-byte blocks for disk usage;
used only with -s and per directory totals
-l use a long listing format
-L, --dereference when showing file information for a symbolic
link, show information for the file the link
references rather than for the link itself
-m fill width with a comma separated list of entries
-n, --numeric-uid-gid like -l, but list numeric user and group IDs
-N, --literal print entry names without quoting
-o like -l, but do not list group information
-p, --indicator-style=slash
append / indicator to directories
-q, --hide-control-chars print ? instead of nongraphic characters
--show-control-chars show nongraphic characters as-is (the default,
unless program is 'ls' and output is a terminal)
-Q, --quote-name enclose entry names in double quotes
--quoting-style=WORD use quoting style WORD for entry names:
literal, locale, shell, shell-always,
shell-escape, shell-escape-always, c, escape
(overrides QUOTING_STYLE environment variable)
-r, --reverse reverse order while sorting
-R, --recursive list subdirectories recursively
-s, --size print the allocated size of each file, in blocks
-S sort by file size, largest first
--sort=WORD sort by WORD instead of name: none (-U), size (-S),
time (-t), version (-v), extension (-X)
--time=WORD with -l, show time as WORD instead of default
modification time: atime or access or use (-u);
ctime or status (-c); also use specified time
as sort key if --sort=time (newest first)
--time-style=TIME_STYLE time/date format with -l; see TIME_STYLE below
-t sort by modification time, newest first
-T, --tabsize=COLS assume tab stops at each COLS instead of 8
-u with -lt: sort by, and show, access time;
with -l: show access time and sort by name;
otherwise: sort by access time, newest first
-U do not sort; list entries in directory order
-v natural sort of (version) numbers within text
-w, --width=COLS set output width to COLS. 0 means no limit
-x list entries by lines instead of by columns
-X sort alphabetically by entry extension
-Z, --context print any security context of each file
-1 list one file per line. Avoid '\n' with -q or -b
--help display this help and exit
--version output version information and exit
The SIZE argument is an integer and optional unit (example: 10K is 10*1024).
Units are K,M,G,T,P,E,Z,Y (powers of 1024) or KB,MB,... (powers of 1000).
The TIME_STYLE argument can be full-iso, long-iso, iso, locale, or +FORMAT.
FORMAT is interpreted like in date(1). If FORMAT is FORMAT1<newline>FORMAT2,
then FORMAT1 applies to non-recent files and FORMAT2 to recent files.
TIME_STYLE prefixed with 'posix-' takes effect only outside the POSIX locale.
Also the TIME_STYLE environment variable sets the default style to use.
Using color to distinguish file types is disabled both by default and
with --color=never. With --color=auto, ls emits color codes only when
standard output is connected to a terminal. The LS_COLORS environment
variable can change the settings. Use the dircolors command to set it.
Exit status:
0 if OK,
1 if minor problems (e.g., cannot access subdirectory),
2 if serious trouble (e.g., cannot access command-line argument).
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation at: <https://www.gnu.org/software/coreutils/ls>
or available locally via: info '(coreutils) ls invocation'
Introduction to Git#
Now that you have a handle on the basic command-line tools, you’re ready to start with Git. Git is a version control system that runs on the command line, which is why we started there.
First, let’s check if Git is installed and what version you have.
git --version
git version 2.28.0
If this command returns a version number (e.g., git version 2.34.1), you’re ready to go. If you get an error, you’ll need to install Git first.
Configuring Git#
The first thing you should do after installing Git is to tell it who you are. This information is attached to every change you make, so it’s important for collaboration.
To set your username and email address for all your projects (globally), use the git config command:
git config --global user.name "msdp-book"
git config --global user.email "msdp.book@gmail.com"
To check your settings, you can list the global configuration:
git config --global --list
user.name=msdp-book
user.email=msdp.book@gmail.com
http.sslverify=false
init.defaultbranch=main
credential.helper=store
Know more: System vs Global vs Local Configuration
Git uses three levels of configuration:
--system: Settings for every user on the computer.--global: Settings for you, the current user, across all your projects.--local: Settings for the specific project (repository) you are currently in. This is the default if you don’t specify a level. Local settings override global settings, which in turn override system settings.