2. Some Basic Unix Commands#
Here are some commonly used Unix commands
ls - list files
man - get information about a unix command
pwd - display present working directory
cp - copy files
mv - move files
rm - remove files
cd - change directory
mkdir - make a directory
rmdir - remove a directory
For example, you can generate a list of files and directories by using the command ls.
ls
_build images notes.txt
_config.yml introduction-to-unix.ipynb _toc.yml
getting-started.ipynb intro.ipynb Untitled1.ipynb
image-creation.odp messages.txt Untitled.ipynb
Notice that the output of the command ls shown above is not on your system (it is on one of mine), so the output will be different.
Most unix commands can accept additional options which modify what the basic command does. For example
ls -l
total 4700
-rw-rw-r-- 1 grosed grosed 198676 Dec 16 10:22 android-architecture.jpg
-rw-rw-r-- 1 grosed grosed 72518 Dec 16 11:49 computer-hardware.jpg
-rw-rw-r-- 1 grosed grosed 539589 Dec 16 11:53 desktop-applications.jpg
-rw-rw-r-- 1 grosed grosed 202835 Dec 16 10:39 desktop-os-statistics.png
-rw-rw-r-- 1 grosed grosed 29663 Dec 16 10:32 device-shipment-2015.png
-rw-rw-r-- 1 grosed grosed 1255 Dec 20 13:19 file-1453.png
-rw-rw-r-- 1 grosed grosed 236442 Dec 20 13:51 file-stdin-cmd-stdout.png
-rw-rw-r-- 1 grosed grosed 237638 Dec 20 13:48 file-stdin-stdout-file.png
-rw-rw-r-- 1 grosed grosed 62234 Dec 20 11:24 introduction-to-unix.ipynb
-rw-rw-r-- 1 grosed grosed 108310 Dec 16 11:40 linux-kernel-code.png
-rw-rw-r-- 1 grosed grosed 47038 Dec 17 13:02 LU-mylab.png
-rw-rw-r-- 1 grosed grosed 275954 Dec 16 13:06 os-components2.png
-rw-rw-r-- 1 grosed grosed 85295 Dec 16 10:01 os-components.png
-rw-rw-r-- 1 grosed grosed 29259 Dec 20 13:49 stdin-cmd-file-cmd-stdout.png
-rw-rw-r-- 1 grosed grosed 11225 Dec 20 13:49 stdin-cmd-pipe-cmd-stdout.png
-rw-rw-r-- 1 grosed grosed 235988 Dec 20 13:47 stdin-stdout-file.png
-rw-rw-r-- 1 grosed grosed 232104 Dec 20 13:46 stdin-stdout.png
-rw-rw-r-- 1 grosed grosed 12139 Dec 17 15:03 terminal-icon.png
-rw-rw-r-- 1 grosed grosed 263810 Dec 16 11:52 terminal.jpg
-rw-rw-r-- 1 grosed grosed 189120 Dec 17 15:05 terminal.png
-rw-rw-r-- 1 grosed grosed 715211 Dec 17 13:06 ubuntu-lab-desktop.png
-rw-rw-r-- 1 grosed grosed 22372 Dec 17 13:04 ubuntu-lab-password.png
-rw-rw-r-- 1 grosed grosed 13427 Dec 17 13:02 ubuntu-lab.png
-rw-rw-r-- 1 grosed grosed 70595 Dec 17 15:00 ubuntu-lab-start-terminal.png
-rw-rw-r-- 1 grosed grosed 22012 Dec 17 13:04 ubuntu-lab-username.png
-rw-rw-r-- 1 grosed grosed 249989 Dec 16 10:22 unix-history.png
-rw-rw-r-- 1 grosed grosed 586762 Dec 17 13:17 waffle-application-launcher.png
Here, the -l options instructs ls to output information regarding the properties of the files being listed.
Unix commands take the general form of
command [-options] <arguments>
2.1. man#
You can find information about a Unix command using the man command. For example
man ls
LS(1) User Commands LS(1)
NAME
ls - list directory contents
SYNOPSIS
ls [OPTION]... [FILE]...
DESCRIPTION
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is speci‐
fied.
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 informa‐
tion 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
change the default of using modification times; access time
(-u): atime, access, use; change time (-c): ctime, status; birth
time: birth, creation;
with -l, WORD determines which time to show; with --sort=time,
sort by WORD (newest first)
--time-style=TIME_STYLE
time/date format with -l; see TIME_STYLE below
-t sort by time, newest first; see --time
-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). Binary prefixes can be used, too: KiB=K, MiB=M, and
so on.
The TIME_STYLE argument can be full-iso, long-iso, iso, locale, or
+FORMAT. FORMAT is interpreted like in date(1). If FORMAT is FOR‐
MAT1<newline>FORMAT2, then FORMAT1 applies to non-recent files and FOR‐
MAT2 to recent files. TIME_STYLE prefixed with 'posix-' takes effect
only outside the POSIX locale. Also the TIME_STYLE environment vari‐
able 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).
AUTHOR
Written by Richard M. Stallman and David MacKenzie.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
COPYRIGHT
Copyright © 2020 Free Software Foundation, Inc. License GPLv3+: GNU
GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
Full documentation <https://www.gnu.org/software/coreutils/ls>
or available locally via: info '(coreutils) ls invocation'
GNU coreutils 8.32 February 2022 LS(1)
2.1.1. Exercise#
List all of the files as before, but print them in a single column
As above, but in date order
Now do both of the above together.
Like many operating systems, Unix organises files into a hierarchy. Files are organised into directories (sometimes referred to as folders by Windows users), and directories can contain sub-directories.
Each file and directory has a name and you can navigate the tree like directory/file structure using Unix shell commands.
2.2. pwd - display present/current/working directory#
pwd
/home/grosedj1
2.3. cd - change present/current/working directory#
Try running the command
cd h-drive
2.3.1. Exercise#
What is the present working directory ?
What files are in your h-drive directory ?
What is the newest file in this directory ?
What is the largest file in this directory ?
Are there any directories in your h-drive ?
Your Unix account has a home directory. It has a nickname ~.
2.3.2. Exercise#
Change the current directory to your home directory. What is your home directory called ?
2.4. mkdir - make a new directory#
To create a directory in your current working directory use the command
mkdir <directory-name>
2.4.1. Exercise#
cd to your home directory and make a new directory called work.
cd into this new directory.
Now create a new directory in your home directory called play- but without changing directories.
2.5. wget - get remote files#
wget is a command that allows you to download a remote file by specifying its URL. Try the following command.
wget http://www.mathsbox.com/introduction-to-unix/files/examples.zip
2.5.1. Exercise#
List the contents of your work directoy.
2.6. unzip#
The file you downloaded using wget is a compressed file. It can be decompressed using the unzip command.
unzip examples.zip
2.7. cp - copy files#
The cp command can be used to copy a file. The syntax is
cp <source> <target>
2.7.1. Exercise#
Copy one or more files from your work directory to your play directory.
2.8. Redirection#
Set the current directory to your home directory and try this -
ls -1 > files.txt
What does it do ?
Hint - try using ls to find out.
The > is called the redirection operator. Normally, the output of ls will go to the terminal. The > operator can be used to send it to other things, such as a file.
2.9. head - display the first few lines#
Try this -
head files.txt
2.9.1. Exercise#
What did you see ?
What does head command do ?
What options does the head command have ?
Try some of these options.
What does the command tail do ?
2.10. echo#
2.10.1. Example#
echo "hello"
hello
2.10.2. Exercise#
Make a new file called messages.txt with the sentence “hello world” in it.
2.10.3. Solution#
echo "hello world" > messages.txt
2.11. wc - count words, lines, and letters#
Try this
wc messages.txt