Important UNIX conventions
1, Command Format
Commands must be typed all on one line, with spaces between the command, options, and arguments.
2,Naming Files
Filenames consist of alphanumeric characters, underscores, dashes, and periods. DO NOT use spaces or other punctuation in filenames!
3,Case Sensitivity
Commands and filenames in UNIX are case sensitive!!
4,Filename Completiom
After typeing a unique prefix of a filename, pressing the Tab key will cause the Unix shell to complete the filename.
5,Command Editing
The up arrow key will retrieve a previous command. This command may be edited using the left/right arrow keys and backspace.
6,^C (control-C)
In UNIX, this terminates a currently running process when typed in the window the process is running in.
7,^Z (control-Z)
In UNIX, this sends a process to run in the background. The process will still exist; you just won't see it. Type "fg" to bring it back so that you can exit properly. Don't exit Unix with processes running in the background.
Working with Directories
0,Directory Notes
In UNIX pathnames, slashes (/) separate the directory and filenames
e.g. /home/mcb/myfile.txt [ here home and mcb are directories and myfile.txt is a file ]. The current directory is referred to as . (‘dot’) and the parent directory is referred to as .. (‘dot dot’). The home directory is called ~ (‘tilde’).
1,Display present working directory
pwd echo present working directory on screen
2,Change directory
cd dirname Change current working directory to specific directory.
cd or cd ~ Go to your home directory, i.e. the directory you start in when you login.
cd .. Go to the parent of the directory you are in now [ move up by 1 directory ]
3,Create/Delete directory
mkdir dirname Creates a directory called dirname in the current directory
rmdir dirname Delete (remove) empty directory
rm –r dirname Delete directory and the content inside it(files,subdirectoris)
4,Lists directory contents
ls dirname lists contents within specific directory
ls –l shows a "long", detailed listing
ls –a lists all of contents ,including hide directoris,files(starting with “.”)
Working with Files
1,Display file content
cat filename display entire file
cat –vet display file including Non-printing characters such as tab,carriage return,linefeed.It’s useful when a file move from windows to unix.
cat filename | less display and navigate file content
2,Rename/Move files
mv file1 file2 rename file1 to file2
mv file dir move the file to the specific directory
3,Copy a file
cp f1 f2 makes a copy of f1,named f2
cp f1 dir copy f1 to a specific directory
4,Delete a file
rm f1 delete a file permanently,Use this command carefully - there is no Undo!!
rm –i f1 ask your confirm before you delete a file. in practice, you can add alias from rm to rm –i in your .bashrc file
5,Change file’s mode(who can operate on the file)
chmod perm f1 change mode of filename as specified by perm(issions). e.g. chmod +x file makes file executable,chmod g-r file removes group read permission on file
Patterns and Counting
1,Pattern
grep pattern files find the lines that meet the pattern
grep –r pattern dir find the lines recursively in a directory. e.g. grep –r fatal /var/log
2,Counting
wc –l count by line,usually get input from pipeline. e.g. cat f1 | wc -l
wc –w count by word
wc –m count by character
Input/Output and Pipelines
0,Input/output notes
By default the output of a command goes to STDOUT (standard output or the monitor), and input of a command comes from STDIN (the keyboard). Input and output can be redirected to/from files with the < , > and >> symbols
1,Redirect
cat f1 f2 > f3 concatenate files f1 and f2 and store the result in file f3. Warning: this overwrites file f3
cat f1 >> f2 concatenate file f1 and append to the contents of f2
sort < f1 > f1.sort sort command reads from f1 and outputs to f1.sort
2,Pipelines notes
Multiple commands can be chained together in a pipeline with the | (‘pipe’) symbol. When | is used between commands, the output of the first command is piped as input to the second command
3,Pipelines
grep “A” f1 | wc –l find lines in f1 containing “A” and pipe them to wc -l Note: this counts the number of lines containing “A”
grep “>” f1 | wc –l note that quoting “>” prevents it from acting as output redirection.
cat f1|sort|head send the contents of f1 to the sort command, then send the sorted lines to the head command to print the top 10.
Finding help
command –help a short usage description
man command manual for a command
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