viverson said:
a table would be nice under basic tools
The Shell - Navigation and Creation
Before Starting this Lesson
You should have Cygwin installed on Windows, or have a bash shell available on other platforms.
Navigating the File System
The easiest way to learn basic Unix commands is to see them in action. For example, type pwd (short for "print working directory”) to find out where you are.
$ pwd /home/hpotter/swc Then type ls (for “listing”) to see what's in the current directory.
$ ls LICENSE.txt conf data docs index.swc license.swc Makefile config.mk depend.mk img lec press
To see what's in the data directory, type ls data.
$ ls data bio elements haiku.txt morse.txt pdb solarsystem.txt
Equivalently, you can type cd data to “go into” the data directory, then type ls. Type cd .. to go back to where you started
$ cd data $ pwd /home/hpotter/swc/data $ ls bio elements haiku.txt morse.txt pdb solarsystem.txt $ cd .. $ pwd /home/hpotter/swc
Execution Cycle
When you type a command like ls, the OS:
• Reads characters from the keyboard
• Passes them to the shell (because it's the currently active window)
The shell:
• Breaks the line of text it receives into words
• Looks for a program with the same name as the first word
• Runs that program
That program's output goes back to the shell…which gives it to the OS…which displays it on the screen.
All well-designed software systems work this way. They break the task down into pieces, write a tool that solves each sub-problem, and then just "hook them up". This allows you to:
• Develop and test components independently
• Replace or re-use components incrementally
• Add new components as you go along
Providing Options
You can make ls produce more informative output by giving it some flags. By convention, flags for Unix tools start with "-" , as in "-c" or "-l". Also, some flags take arguments (such as filenames).
Show directories with trailing slash:
$ ls -F
LICENSE.txt conf/ data/ docs/ index.swc license.swc
Makefile config.mk depend.mk img/ lec/ press/
Show all files and directories, including those whose names begin with "." (by default, ls doesn't show things whose names begin with ".". This means . and .. don't always show up. (We'll see what the .svn directory is for later)
$ ls -a
. .svn Makefile config.mk depend.mk img lec
.. LICENSE.txt conf data docs index.swc
Flags can be combined
$ ls -a -F
. .svn/ Makefile config.mk depend.mk img/ lec/
.. LICENSE.txt conf/ data/ docs/ index.swc
Creating Files and Directories
Rather than messing with the course files, let's create a temporary directory and play around in there:
$ mkdir tmp
(Note: this produces no output, but -v (“verbose”) would tell mkdir to print a confirmation message)
Now go into that directory - there are no files there yet.
$ cd tmp
$ ls
Use the editor of your choice to create a file called earth.txt with the following contents:
Name: Earth Period: 365.26 days Inclination: 0.00 Eccentricity: 0.02You can use Notepad (on Windows), which runs in a window of its own. You can also use Pico (on Unix), which takes over the shell window temporarily. The easiest way to create a similar file venus.txt is to copy earth.txt and edit it:
$ cp earth.txt venus.txt
$ edit venus.txt
$ ls -t
venus.txt earth.txt
Note: -t tells ls to list by modification time, instead of alphabetically
Looking at Files
You can check the contents of the file using cat (short for “concatenate”), which prints the contents of a file to the screen.
$ cat venus.txt
Name: Venus
Period: 224.70 days
Inclination: 3.39
Eccentricity: 0.01
You can also compare the sizes of the two files using: ls -l (“-l” meaning “long form”)
Note the fifth column is size in bytes:
$ ls -l
total 2
-rwxr-xr-x 1 gvwilson None 73 Jan 4 15:58 earth.txt
-rwxr-xr-x 1 gvwilson None 73 Jan 4 15:58 venus.txt
Another way to compare is using wc (for “word count”). The columns show lines, words, and characters:
$ wc earth.txt venus.txt
4 9 73 earth.txt
4 9 73 venus.txt
8 18 146 total
Basic Tools
man | Documentation for commands. |
cat | Concatenate and display text files. |
cd | Change working directory. |
clear | Clear the screen. |
cp | Copy files and directories. |
date | Display the current date and time. |
diff | Show differences between two text files. |
echo | Print arguments. |
head | Display the first few lines of a file. |
ls | List files and directories. |
mkdir | Make directories. |
more | Page through a text file. |
mv | Move (rename) files and directories. |
od | Display the bytes in a file. |
passwd | Change your password. |
pwd | Print current working directory. |
rm | Remove files. |
rmdir | Remove directories. |
sort | Sort lines. |
tail | Display the last few lines of a file. |
uniq | Remove adjacent duplicate lines. |
wc | Count lines, words, and characters in a file. |
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© 2008 Vicki Iverson, All Rights Reserved.
