 |
|
 |
Quick reference to simple Unix commands
|
-
Introduction:
There are only a few commands that you have to know in order to get started on Unix. These will be presented in this introduction. For a more detailed description of the syntax od the commands and available options, you can consult the help files ( so called manual pages ) on the computer, or read a good Unix book.
I know that it is quite boring starting to read books. I hope that you will enjoy this quick reference.
Unix commands sometimes have cryptic names and a very strict calling sequence for their options and parameters. The commands are case senitive, as are the file names on the system, but most of the Unix commands are lower case letters. Options are usually preceded by a "-" sign,or sometimes by a "+" sign.
The general syntax is :
command – options parameter
As usual there are exceptions. Most commands allow more than one option. Theses options can either be put individually on the command line ( e.g. cmd –1 –2 –3 … ) or combined to a single option string ( cmd –123 … )
-
File and Directory Names:
Unix has a tree like file and directory structure, where you can address any file or directory with its absolute path name starting at the file system root ( denoted by / ), or with a name relative to the current position in the file tree.
.
|
the dot denotes the current working directory
|
..
|
two dots denote the directory above the current one
|
/sbin/lib/joe
|
is an absolute path name for the command file joe
|
../otherdir
|
is a directory parallel to the current
|
subdirectory
|
is the name of a subdirectory below the current one
|
~
|
is your home directory
|
~marc
|
home directory of the user marc
|
.controlfile
|
name of a control file in the current directory ( e.g. for mail, editors, … )
usually these "dotted files" are found in the home directory
|
-
Manipulate Files:
Wildcards ( ? single character, * word ) are very useful in handling files. Be very careful when you use wildcards with the copy, move or remove command. Unix will delete or overwrite existing files without warning. Normaly the cannot be restored.
cat name
|
list file with name name
|
head name
|
list first 10 lines of file ( option –number, e.g. head –20 for the first 20 lines)
|
tail name
|
list last 10 lines of file ( option –number, e.g. tail –20 for the last 20 lines)
tail –f continuously lists the end of a file : This can be used to check the system.
tail –f /var/log/mail shows what sendmail is working
|
less name
|
list file page by page
|
cp name newname
|
copy file to new name or new directory
|
mv name newname
|
move file to new name or new directory
|
rm name
|
remove file ( At the beginning please use the option –i in order to be prompted before deletion
rm * will remove all files in the directory
|
file name
|
analyse file type and contents
|
find path-name expression
|
find a file in the file tree (relatively slow) |
-
Manipulate Directories:
mkdir name
|
create a directory with name name
|
mkdir name
|
remove a (empty)directory with name name
|
cd name
|
change to working directory with the name name
|
pwd
|
print working directory ( = print name of the current working directory )
|
ls name
|
list contents of the directory with the name name
( = under DOS =: dir )
if name is omitted, the current working directory is listed
options : ls -lsa
-l long detailed listing ( owner group rights ...)
-s shows the file size in KB
-a lists also the dotted files
|
-
Miscellaneous Commands
chmod rights file
|
change access rights ( who±right )of files or directories,
e.g. chmodg+x filename will add execution right for members of the group
chmodu+x filename will add execution right for user
chmodg+rwx filename will add reading, writing, execution right for members of the group
|
who
|
list all logged in users on local machine
|
passwd
|
change your password
|
finger user@host
|
list information about ussers on local or remote machines
|
last
|
display last login information of users on the system
|
grep string file
|
find a string or regular pattern in a file
|
diff file1 file2
|
display differences between two text files
|
tar
|
tape file archiver ( files with name.tar )
|
su user
|
change the user
|
-
Root Commands
chown user.group file
|
change owner and group of files or directories,
|
chgrp group file
|
change possesion of files or directories,
|
shutdown
|
switch off the server
|
reboot
|
shutdown the server and restarts it
|
 |
 |
|
|
