Transcript Common commands

"Two of the
most famous
products of
Berkeley are
LSD and Unix.
I don't think
that this is a
coincidence.”
Anonymous
Basics of the Unix/Linux
Environment
Common Commands
Making directories
 mkdir: make directory
% mkdir bin src Projects Classes
Makes 4 directories: bin, src, Projects, and Classes in the
working directory.
Removing Directories
 rmdir: remove directory; only works with empty
directories but is safe
% rmdir bin src Projects Classes
Removes the 4 directories bin, src,
Projects, and Classes in the working
directory -- if they are EMPTY.
Removing files and directories
 rm: remove files and directories; a very straightforward
and DANGEROUS command
There is no trash can on a unix machine.
CERI accounts are set up so that rm is aliased to rm –
i, which means the computer will ask you if you
really want to remove the file(s) one at a time
%which rm
rm:
aliased to /bin/rm –i
%rm file1
remove file1? yes
%
Valid answers.
Yes, yes, Y, y – to accept and erase.
No, no, N, n – to not erase.
<CR> - does not erase.
Something it does not understand – does not erase.
 rm –d: remove directory like rmdir
 rm –r: remove directory and all subdirectories and files;
implies –d; can be very dangerous… one typo could
remove months of files
% rm -r Classes
 \rm: You can return to the original definition of rm using
the “\”. You will no longer be prompted before a file is
removed so don’t make a typo
Looking at files
 more: browse or page through a text file; opens file
quickly and pages down full screen; use space bar to
page down
 less: same as more but allows forward and backward
paging; in OSX, more is aliased to less because less
is more with additional features
Looking at files continued
 head -nX: prints the first X number of lines to the
screen; default is 10 lines if -n is not specified
 tail -nX: prints the last X number of lines to the
screen; default is 10 lines if -n is not specified
(mac/linux)
 tail -Xf: prints the last X number of lines to the screen;
default is 10 lines if -f is not specified (ceri suns)
Manipulating files
 cat: concatenate files into a single column; it dumps the
entire file contents to the screen unless redirected to a file
o Since it dumps the entire file contents to the screen, we can
use it to “print out” or ”type out” a file.
%cat dead.letter
Hello...testing
Another Unix philosophy issue – use of side effects.
We don’t need another command to print or type the contents
of a file to the screen as it is a side effect of the cat
command.
 Example: make one file out of file1, file2 and file3 and
call it alltogether.
%cat file1 file2 file3 > alltogether
or
%cat file1 file2 file3
 This command (does not need input redirection,
exception to regular rule that input comes from
Standard IN) takes files file1, file2, and file3 and puts
them into file alltogether or you can skip creating the
file alltogether
 Creating files using cat - type the command
%cat > name_of_file
Now type in your text. Press the <Return> key to start a
new line. When you have finished typing in your text,
enter Ctrl-d (Press and hold down the Ctrl key and type
a "d"). This stops the cat command and returns you to
the system prompt.
%cat > test.file
Hello everyone<CR>
CNTL-D
%more test.file
Hello everyone
 paste: concatenate files with each file a new column;
when used on a single file, it dumps the entire file
contents to the screen
Piping and Redirect
 Input and output on the command line are
controlled by the |, >, <, and ! symbols
 | : pipe function; sends the output from
command on left side as input to the command
on the right side
% cd SACdata
% ls | head -n5
1002
1019
1023
1045
1046
Piping and Redirect
 > : redirect standard output (screen) to a specific file*
% cd SACdata
% ls | head -n5 > directory.list
% more directory.list
1002
1019
1023
1045
1046
* In tcsh, this will not overwrite a pre-existing file
with the same name. In bash shell, the >
overwrites any pre-existing file with no warning
Piping and Redirect
 >! : redirect standard output (screen output) to a specific
file and overwrite the file if it already exists *
% ls | head –n5 >! directory.list
% more directory.list
1002
1019
1023
1045
1046
*This syntax is specific to tcsh, your default CERI
shell; in bash this will put the output into a file
named !
Piping and Redirect
 >> : concatenate standard output (screen output) to the
end of a specific file
% ls | head –n2 >! directory.list
% ls | tail –n2 >> directory.list
% more directory.list
1002
1019
tmp
tmp.file
 < : redirect file on right as input to command
on the left
% head –n1 < suma1.hrdpicks
1 51995 31410273254
30870
958490 297
Copying, moving, or linking
files & directories
 cp: copy files
 cp -r: copy directory and all files & subdirectories
within it
% cp file1 Project/SUMATRA/file2
% cp file1 Project/SUMATRA/.
 mv: move files or directories
% mv file1 file2 Project/SUMATRA/.
 If you want to change the names when you move them,
you have to do them one at a time
% mv file1 ESCI7205/HW/HW1
% mv file2 ESCI7205/HW/HW2
 ln -s: create a symbolic link between two files
% ln –s sourcefile1 Project/SUMATRA/targetfile1
% ln –s sourcefile1 Project/SUMATRA/.
This makes the file show up in the new directory (the target)
listing, but the file really only exists in the original place.
Wildcards
 Wildcards all you to match multiple instances of
characters/numbers in file or directory names
 They can be used in combination with almost all unix
commands
 Wildcards are essential when dealing with large
amounts of geophysical data
Wildcards
 * : represents zero or more characters or numbers
% ls 2/*.BHZ.*
2/HIA.BHZ.SAC
2/filt.HIA.BHZ.SAC
2/WMQ.BHZ.SAC
2/filt.WMQ.BHZ.SAC
% ls 2/f*.BHZ.*
2/filt.HIA.BHZ.SAC
2/filt.WMQ.BHZ.SAC
 ? : represents a single character or number
% ls 2/HIA.BH?.*
2/HIA.BHE.SAC
2/HIA.BHZ.SAC
2/HIA.BHN.SAC
Wildcards
 [] : single placeholder used to specify a range of
characters or numbers rather than all possible
characters or numbers
% ls 2/HIA.BH[E,N,Z].*
2/HIA.BHE.SAC
2/HIA.BHN.SAC
2/HIA.BHZ.SAC
% ls */HIA*198[0-9]*
795/HIA.BHZ.D.1988.041:07.18.30
799/HIA.BHZ.D.1988:14:35:27.00
812/HIA.BHZ.D.1988:03:43:49.00
813/HIA.BHZ.D.1988.362:13.58.59
814/HIA.BHZ.D.1989.041:17.07.43
CNTL-C
 Use CNTL-C to quit a job
 If you accidently start something that isn’t working,
CNTL-C will quit and return you to a blank command
line
See this link for a list and
description of many Unix
commands
http://pcsplace.com/tech-list/ultimate-list-of-linuxand-unix-commands/