Métodos Numéricos para la Astronomía 2016A Licenciatura en Astronomía Departamento de Física y Astronomía, Facultad de Ciencias. Universidad de La Serena Clase 5 José Luis Nilo Castellón
Unix Architecture
hardware es la mas profunda estando formada por los componentes físicos de tu computador. Envolviendo a ésta, viene la capa del kernel que es el corazón de Linux, su núcleo, y es quien hace que el hardware funcione, efectuando su manejo y control. Los programas y comandos que envuelven el kernel, lo utilizan para realizar las tareas especificas para las cuales fueron desarrolladas. Encerrando todo eso viene el Shell que tiene este nombre porque en ingles, Shell significa concha, envoltura, o sea que, queda entre los usuarios y el sistema operativo, de forma que todo lo que interacciona con el sistema operativo, tiene que pasar por su filtro.
Unix History and Motivation The first version of Unix came from AT&T in the early 1970s (Unix is old!). Unix was developed by programmers and for programmers. Unix is designed so that users can extend the functionality To build new tools easily and efficiently To customize the shell and user interface. To string together a series of Unix commands to create new functionality. To create custom commands that do exactly what we want.
What is Shell? Shell is Command Interpreter that turns text that you type (at the command line) in to actions: User Interface: take the command from user Programming Shell can do Customization of a Unix session Scripting
Programming languages are generally a lot more powerful and a lot faster than scripting languages. Programming languages generally start from Programming or Scripting? bash is not only an excellent command line shell, but a scripting language in itself. Shell scripting allows us to use the shell's abilities and to automate a lot of tasks that would otherwise require a lot of commands. Difference between programming and scripting languages:
Customization of a Session Each shell supports some customization. User prompt Where to find mail Shortcuts (alias) The customization takes place in startup files Startup files are read by the shell when it starts up The Startup files can differ for different shell
Types of Shells Interactive vs. Non-interactive; login or not Interactive login shell started after login Non-interactive shell Present when shell script is running Just inherits parent s environment Interactive non-login shell started Started from a command line Copies parent environment then invokes ~/.bash_rc (or ~/.cshrc or ~/.tcshrc)
Popular Shells sh ksh Bourne Shell Korn Shell csh,tcsh C Shell (for this course) bash Bourne-Again Shell
Una visión rápida em los Principales Sabores de Shell Bourne Shell (sh) Desarrollado por Stephen Bourne de la Bell Labs (de AT&T donde también fue desarrollado el Unix), este fue durante muchos años el Shell patrón del sistema operativo Unix. Es también llamado de Standard Shell por haber sido durante varios años, el único y hasta hoy es el mas utilizado ya que fue transportado para todos los ambientes Unix y distros Linux. Korn Shell (ksh) Desarrollado por David Korn, también de la Bell Labs, es un superconjunto del sh, o sea, posee todas las facilidades del sh y a ellas se agregaron muchas otras. La compatibilidade total con el sh esta atrayendo a muchos usuarios y programadores de Shell para este ambiente. Boune Again Shell (bash) Este es el Shell mas moderno y cuyo número de adeptos crece mas en todo el mundo, sea por ser el Shell default de Linux, su sistema operativo natural, o sea por su gran diversidad de comandos, que incorpora inclusive diversas instrucciones características del C Shell. C Shell (csh) Desarrollado por Bill Joy de la Berkley University es el Shell mas utilizado en ambientes*bsd e Xenix. La estrutura de sus comandos es bastante similar al del lenguage C. Su gran pecado fue ignorar la compatibilidad con el sh, partiendo por un camino propio.
El Shell es el primer programa al que accedes al loguearte en Linux. Es él quien va a resolver una cantidad de cosas para no cargar al kernel con tareas repetitivas, aliviandolo para tratar asuntos mas importantes. Como cada usuario posee su propio Shell interponiendose entre él y el Linux, es el Shell quien interpreta los comandos que son tecleados y examina sus sintaxis, pasándolos desmenuzados para su ejecución.
Connecting to a Unix/Linux system Open up a terminal:
Connecting to a Unix/Linux system Open up a terminal: The prompt The current directory ( path ) The host
What exactly is a shell? After logging in, Linux/Unix starts another program called the shell The shell interprets commands the user types and manages their execution The shell communicates with the internal part of the operating system called the kernel The most popular shells are: tcsh, csh, korn, and bash The differences are most times subtle For this tutorial, we are using bash Shell commands are CASE SENSITIVE!
Help! Whenever you need help with a command type man and the command name
Help!
Help!
Help!
Unix/Linux File System NOTE: Unix file names are CASE SENSITIVE! /home/mary/ /home/john/portfolio/ The Path
Command: pwd To find your current path use pwd
Command: cd To change to a specific directory use cd
Command: cd ~ is the location of your home directory
Command: cd.. is the location of the directory below current one
Command: ls To list the files in the current directory use ls
Command: ls ls has many options -l long list (displays lots of info) -t sort by modification time -S sort by size -h list file sizes in human readable format -r reverse the order man ls for more options Options can be combined: ls -ltr
Command: ls -ltr List files by time in reverse order with long listing
General Syntax: * * can be used as a wildcard in unix/linux
Command: mkdir To create a new directory use mkdir
Command: rmdir To remove and empty directory use rmdir
Creating files in Unix/Linux Requires the use of an Editor Various Editors: 1) nano / pico 2) vi 3) emacs
Editing a file using pico or nano Type pico or nano at the prompt
Editing a file using pico To save use ctrl-x
Displaying a file Various ways to display a file in Unix cat less head tail
Command: cat Dumps an entire file to standard output Good for displaying short, simple files
Command: less less displays a file, allowing forward/backward movement within it return scrolls forward one line, space one page y scrolls back one line, b one page use / to search for a string Press q to quit
Command: head head displays the top part of a file By default it shows the first 10 lines -n option allows you to change that head -n50 file.txt displays the first 50 lines of file.txt
Command: head Here s an example of using head :
Command: tail Same as head, but shows the last lines
File Commands Copying a file: cp Move or rename a file: mv Remove a file: rm
Command: cp To copy a file use cp
Command: mv To move a file to a different location use mv
Command: mv mv can also be used to rename a file
Command: rm To remove a file use rm
Command: rm To remove a file recursively : rm r Used to remove all files and directories Be very careful, deletions are permanent in Unix/Linux
File permissions Each file in Unix/Linux has an associated permission level This allows the user to prevent others from reading/writing/executing their files or directories Use ls -l filename to find the permission level of that file
Permission levels r means read only permission w means write permission x means execute permission In case of directory, x grants permission to list directory contents
File Permissions User (you)
File Permissions Group
File Permissions The World
Command: chmod If you own the file, you can change it s permissions with chmod Syntax: chmod [user/group/others/all]+[permission] [file(s)] Below we grant execute permission to all:
Running a program (a.k.a. a job) Make sure the program has executable permissions Use./ to run the program
Running a program: an example Running the sample perl script hello_world.pl
Ending a program To end a program use ctrl-c. To try it:
Command: ps To view the processes that you re running:
Command: top To view the CPU usage of all processes:
Command: kill To terminate a process use kill
Input/Output Redirection ( piping ) Programs can output to other programs Called piping program_a program_b program_a s output becomes program_b s input program_a > file.txt program_a s output is written to a file called file.txt program_a < input.txt program_a gets its input from a file called input.txt
A few examples of piping
A few examples of piping
Command: wc To count the characters, words, and lines in a file use wc The first column in the output is lines, the second is words, and the last is characters
A few examples of piping
Command: grep To search files in a directory for a specific string use grep
Command: diff To compare to files for differences use diff Try: diff /dev/null hello.txt /dev/null is a special address -- it is always empty, and anything moved there is deleted
ssh, scp ssh is used to securely log in to remote systems, successor to telnet ssh [username]@[hostname] Try: ssh yourusername@localhost Type exit to log out of session Scp is used to copy files to/from remote systems, syntax is similar to cp: Try: scp [local path] [usernme]@[hostname]:[remote file path] scp hello.txt yourusername@localhost:scp-test.txt
Unix Web Resources http://www.ee.surrey.ac.uk/teaching/unix/ http://www.ugu.com/sui/ugu/show?help. beginners http://en.wikipedia.org/wiki/unix