Perform a listing of the given path or your current directory.
Common options: -l, -h, -a
cd
this command to make you enter “go inside or outside” a path
Change into the given path or into your home directory.
## here is some description for cd path :
Path
it is A description of where a file or directory is on the filesystem.
Absolute Path
One beginning from the root of the file system (eg. /etc/sysconfig ).
Relative Path
One relative to where you currently are in the system (eg. Documents/music ).
~ (tilde)
Used in paths as a reference to your home directory (eg. ~/Documents ).
. (dot)
Used in paths as a reference to your current directory (eg. ./bin ).
.. (dot dot)
Used in paths as a reference to your current directories parent directory (eg. ../bin ).
TAB completion
Start typing and press TAB. The system will auto complete the path. Press TAB twice and it will show you your alternatives.
file followed with path
Find out what type of item a file or directory is.
Spaces in names
Put whole path in quotes ( “ ) or a backslash ( \ ) in front of spaces.
Hidden files and directories
A name beginning with a . (dot) is considered hidden.
Manual Pages
man
View the man page for a command.
man -k
Search for man pages containing the search term.
n
After performing a search within a manual page, select the next found item.
Press q to exit man pages
File Manipulation
mkdir
this will Create a directory
rmdir
this will Remove a directory (only if empty).
touch
Create a blank file.
cp
Copy the source file to the destination.
mv
Move the source file to the destination.
May also be used to rename files or directories.
rm
Remove a file or directory.
Common options: -r -f
Filters
.head
Show the first n lines.
.tail
Show the last n lines.
.sort
Sort lines in a given way.
.wc
How many words, characters and lines.
.grep
Search for a given pattern.
also
Redirect STDOUT to a file.
Append STDOUT to the end of a file.
2>
Redirect the STDERR to a file.
<
Pass the contents of a file to a program as STDIN.
|
Feed the STDOUT of the program on the left as STDIN to the program on the right.
Process Management
CTRL + C
Cancel the currently running process.
kill
Cancel the given process.
Include the option -9 to kill a stubborn process.
ps
Obtain a listing of processes and their id’s.
Including the option aux will show all processes.
CTRL + Z
Pause the currently running process and put it in the background.
jobs
See a list of current processes in the background.
fg
Move the given process from the background to the foreground.
du -sh ./*
Find the size of every directory in your current directory.
df -h
Display how much disk space is used and also free.
Make a copy of every jpg image file in the current directory and rename adding _original.
find /home -mtime -1
Find all files in the given directory (and subdirectories) which have been modified in the last 24 hours.
shutdown -h now
cat
View a file.
### less
less allows you to move up and down within a file using the arrow keys
vi
edit file
Wildcards may be used at any part of a path.
Wherever a path is used
Because wildcard substitution is done by the system, not the command, they may be used wherever a path is used.
ex: * ? []
chmod
Change permissions on a file or directory.
#### nl
. nl - s ` . ` -w num
-s specifies what should be printed after the number while the second one -w specifies how much padding to put before the number.
#### word count wc
By default it will give a count of all
option : -l / -lw
#### Stream Editor sed
#### uniq
Remove duplicate lines.
tac
Print the data in reverse order.
top
a program make snapshot of what is currently happening on the system
egrep
egrep is a program which will search a given set of data and print every line which contains a given pattern
options :
. (dot) - a single character.
? - the preceding character matches 0 or 1 times only.
* - the preceding character matches 0 or more times.
##### + - the preceding character matches 1 or more times.
{n} - the preceding character matches exactly n times.
{n,m} - the preceding character matches at least n times and not more than m times.
[agd] - the character is one of those included within the square brackets.
[^agd] - the character is not one of those included within the square brackets.
[c-f] - the dash within the square brackets operates as a range. In this case it means either the letters c, d, e or f.
() - allows us to group several characters to behave as one.
| (pipe symbol) - the logical OR operation.
^ - matches the beginning of the line.
$ - matches the end of the line.
### ps
which stands for processes. In it’s normal usage it will show you just the processes running in your current terminal (which is usually not very much). If we add the argument aux then it will show a complete system view which is a bit more helpful.
##### option :
###### aux hen it will show a complete system view which is a bit more helpful.
jobs
Display a list of current jobs running in the background.
fg
Move a background process into the foreground
#!
Shebang. Indicates which interpreter a script should be run with.
echo
Print a message to the screen.
which
Tells you the path to a particular program.
$
Placed before a variable name when we are referring to it’s value.
` `
Backticks. Used to save the output of a program into a variable.
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