A Genomics View of Unix

Transcription

1 A Genomics View of Unix Genomics Requires Powerful Computers Genomic data sets are large and complex, the requirements for computing power are also quite large Computers that can provide this power generally use the Unix operating system - so you must learn Unix The mac OS X is based on Unix most of the Unix information is true for your mac simply open Terminal inside X11 and you can control your powerbook with unix commands Unix Advantages It is very popular, so it is easy to find information and get help Lots of books plenty of helpful websites USENET discussions (google groups) and lists most Comp. Sci. students know Unix Unix can run on virtually any computer (IBM, Sun, Compaq, Macintosh,etc) Unix is free or nearly free Linux/open source software movement Suse, FreeBSD, Red Hat, LinuxPPC, etc. Stable and Efficient Unix is very stable - computers running Unix almost never crash Unix is very efficient it gets maximum number crunching power out of your processor (and multiple processors) it can smoothly manage very large amounts of data Most bioinformatics software is created for Unix - its easy for the programmers 1

2 Unix has some Drawbacks Unix computers are controlled by a command line interface NOT user-friendly difficult to learn, even more difficult to truly master Hackers love Unix there are lots of security holes most computers on the Internet run Unix, so hackers can apply the same tricks to many different computers There are many different versions of Unix with subtle (or not so subtle) differences General Unix Tips UNIX is case sensitive!! myfile.txt and MyFile.txt do not mean the same thing You communicate with a Unix computer through a command program known as a shell. The shell interprets the commands that you type on the keyboard Advanced users can write shell scripts to automate program execution, important for large (genomic size) datasets Tips..Control Characters You type Control characters by holding down the ctrl key while also pressing the specified character. While you are typing a command: ctrl-u erases the whole command line Control commands that work (almost) any time ctrl-s suspends (halts) output scrolling up on your terminal screen ctrl-q resumes the display of output on your screen ctrl-c will abort any program ctrl-z will pause any program Getting Help in Unix Unix is not a user-friendly computer system. While not actively user-hostile, it is perfectly happy to sit there and taunt you with a blank screen and a blinking > cursor. There is a rudimentary Help system which consists of a set of "manual pages for every Unix command. The man pages tell you which options a particular command can take, and how each option modifies the behavior of the command. Type man and the name of a command to read the manual page for that command. 2

3 Apple s OS X man page for ls More Help (?) LS(1) System General Commands Manual LS(1) NAME ls - list directory contents SYNOPSIS ls [-ACFLRSTWacdfgiklnoqrstux1] [file...] DESCRIPTION For each operand that names a file of a type other than directory, ls displays its name as well as any requested, associated information. For each operand that names a file of type directory, ls displays the names of files contained within that directory, as well as any requested, associated information. If no operands are given, the contents of the current directory are displayed. If more than one operand is given, non-directory operands are displayed first; directory and non-directory operands are sorted separately and in lexicographical order. The following options are available: -A List all entries except for `.' and `..'. Always set for the So what if you don t know what command you need? You can search the manual pages for a given keyword in the header: man -k E.g. to get help on commands that deal with passwords you would type: man -k password Apropos works on some unix systems as well, try man apropos on other unix systems for help Get yourself a good "Intro to Unix" book Unix Help on the Web Here is a list of a few online Unix tutorials: Unix for Beginners Getting Started in Unix Unix Guru Universe Getting Started With The Unix Operating System You will need to be able to: Type and understand basic commands Manipulate files (copy, delete, examine etc) Run Bioinformatic programs (consed, etc) Understand files and directories 3

4 Unix Commands Most commands have this basic structure: command -a -b -c input.file Program modifiers input Program: the name of the program you want to run (blast, consed, etc.) Modifiers (optional, usually in any order): a CASE SENSITIVE letter which controls exactly how the program will run Some will be plain -l some will have values -l guest Input (optional): the file(s) you wish the program to act upon. Unix Commands (cont) Many Unix commands are short and cryptic like vi or rm. Computer geeks like it that way. The more you use it the more you will like it Every command has a host of modifiers which are generally single letters preceded by a hyphen: ls -l or mv -R Capital letters have different functions than small letters, often completely unrelated. A command also generally requires one or more arguments, meaning some file on which it will act: cat -n mygene.seq Lets change your Password 1. Start X11 click on icon at bottom 2. You should see a window xterm show up where you can type commands 3. Type: passwd This command has no arguments 4. enter current password (dna50) 5. enter new password 2X 6. DO NOT FORGET! Unix Filenames Unix is case sensitive UNIX filenames should contain only letters, numbers, and the _ (underscore),. (dot), and - (dash) characters. Unix does not allow two files to exist in the same directory with the same name. Whenever a situation occurs where a file is about to be created or copied into a directory where another file has that exact same name, the new file will overwrite (and delete) the older file. Unix will generally alert you when this is about to happen, but it is easy to ignore the warning. 4

5 Filename Extensions By convention most UNIX filenames start with a lower case letter and end with a dot followed by one, two, or three letters (or more): myfile.txt However, this is just a common convention and is not required. It is also possible to have additional dots in the filename. The part of the name following the dot is called the extension. The extension is used to designate the file type This convention is used to help you remember what the file is. Unix does not require extensions. Some Common Extensions By convention files that end in :.txt are text files.html are HTML files for the Web.zip or.gz are compressed files.fasta are DNA or peptide sequences in fasta format.seq or.pep are DNA or protein sequences Files can have more than one extension. Compressed text files would end.txt.gz Unix directories Unix systems can have many thousands of files Directories are a means of organizing your files on a Unix computer. They are equivalent to folders in Windows and Macintosh computers Start with the root directory: / There are files and directories inside root There are files and other directories inside those There are files and other directories inside those.. Unix directories (cont) When logged into a computer there is always one directory called the current working directory. The computer will look for files in the current working dir, unless told specifically where to look. 5

6 Unix directories (cont) A list of all the directories to a file is called the path. The path can either start at root / /Users/chris/Documents/4342files/2004/lecture1.ppt Or the current working directory Documents/4342files/2004/lecture1.ppt Your Home Directory When you login to any Unix server, you always start in your Home directory. On Mac my home is /Users/chris Create sub-directories to store specific projects or groups of information, just as you would place folders in a filing cabinet. Do not accumulate thousands of files with cryptic names in your Home directory File & Directory Commands This is a minimal list of Unix commands that you must know for file management: ls (list files) cd (change directory) mkdir (make directory) rmdir (remove directory) cp (copy file) pwd (present working directory) mv (move file) rm (remove) more (view by page) cat (dump file on screen) All of these commands can be modified with many options. Learn to use Unix man pages for more information. Navigation pwd (present working directory) shows the name of the current working directory: > pwd /Users/chris ls (list) gives you a list of the files in the current directory: Desktop Library Public Documents Movies Sites Use the ls -l (long) option to get more information ~/ >ls -l total 0 drwx chris staff 340 Mar 9 11:11 Desktop drwx chris staff 442 Mar 9 11:11 Documents drwx chris staff 952 Feb 21 10:42 Library drwx chris staff 102 Dec 20 21:16 Movies 6

7 Sub-directories cd (change directory) set a new current working dir >cd Documents > pwd /Users/chris/Documents mkdir (make directory) creates a new sub-directory inside of the current directory Leah.cvs splitgti.pl > mkdir subdir Leah.cvs splitgti.pl subdir rmdir (remove directory) deletes a sub-directory, but the sub-directory must be empty > rmdir subdir Leah.cvs splitgti.pl Shortcuts There are some important shortcuts in Unix for specifying directories. (dot) means "the current directory".. means "the parent directory" - the directory one level above the current directory, so cd.. will move you up one level ~ (tilde) means your Home directory, so cd ~ will move you back to your Home. Just typing a plain cd will also bring you back to your home directory Commands for Files Files are used to store information, for example, DNA sequence data or the results of some analysis. You will mostly deal with text files cat dumps the entire contents of a file onto the screen. For a long file this can be annoying, but it can also be helpful if you want to copy and paste from your screen More Use the command more to view the contents of a file one screen at a time: > more t27054_cel.pep!!aa_sequence 1.0 P1;T protein Y49E Caenorhabditis elegans Length: 534 May 30, :49 Type: P Check: MLKKAPCLFG SAIILGLLLA AAGVLLLIGI PIDRIVNRQV IDQDFLGYTR 51 DENGTEVPNA MTKSWLKPLY AMQLNIWMFN VTNVDGILKR HEKPNLHEIG 101 PFVFDEVQEK VYHRFADNDT RVFYKNQKLY HFNKNASCPT CHLDMKVTIP t27054_cel.pep (87%) Hit the spacebar to page down through the file b moves back up a page At the bottom of the screen, more shows how much of the file has been displayed /pattern searches ahead for pattern 7

8 Copy & Move cp lets you copy a file from any directory to any other directory, or create a copy of a file with a new name in one directory cp file.ext newname.ext cp file.ext subdir/newname.ext cp /Users/chris/file.ext./subdir/newfilename.ext mv allows you to move files to other directories, but it is also used to rename files. Filename and directory syntax for mv is exactly the same as for the cp command. mv filename.ext subdir/newfilename.ext NOTE: When you use mv to move a file into another directory, the current file is deleted. Delete Use the command rm (remove) to delete files There is no way to undo this command!!! some Unix setup s will ask you to confirm others will not. Be aware of this when deleting af gb_pr5 test.seq > rm test.seq af gb_pr5 Wildcards You may often want to work on more than one file at a time. You can use wildcard symbols to do this. You can substitute the * as a wildcard symbol for any number of characters in any filename. If you type just * after a command, it stands for all files in the current directory: cat * will dump all files to the screen You can mix the * with other characters to form a search pattern: a*.txt would be a list all files that start with a and end in.txt The? wildcard stands for any single character: draft?.doc would match draft1.doc, draft2.doc, draftb.doc, etc. Two Tricks for everyone Command History Filename completion 8

9 Command history The computer remembers you last 100 or so commands. Use the up arrow to scroll back through these commands. You can use right and left arrow to move around inside the command to edit it Very nice for long commands (e.g. blast searches) Command history The computer remembers you last 100 or so commands. Use the up arrow to scroll back through these commands. You can use right and left arrow to move around inside the command to edit it Very nice for long commands (e.g. blast searches) Files name completion Since the computer will only look in the current working dir for files when you want to type in a file name all you have to type is enough characters at the beginning to uniquely define the file When you hit <TAB> the shell will finish typeing the name for you af gb_pr5 test.seq apt.txt > rm af <hit tab> > rm af gb_pr5 Have long names but keep the differences at the beginning to facilitate using this feature 9