AOS Lab 1: Hello, Linux!
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This document provides an introduction to Linux and common Linux commands. It discusses key facts about Unix, how Linux is based on Unix, popular Linux distributions like Ubuntu, and common file system layout and commands for manipulating files and directories. The document concludes with an assignment to write a Bash script to analyze and compare British and American English dictionaries.
AOS Lab 1: Hello, Linux!
- 1. Lab 1: Hello, Linux! Advanced Operating Systems Zubair Nabi zubair.nabi@itu.edu.pk January 23, 2013
- 2. Unix • Multi-task, multi-user OS out of Bell Labs in 19691 • Initially in Assembly but later in C (1973)2 • Code recycling! • Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, Michael Lesk and Joe Ossanna • Branched into BSD (FreeBSD, NetBSD, etc.) 1 2 http://www.youtube.com/watch?v=tc4ROCJYbm0 Dennis M. Ritchie and Ken Thompson. 1974. The UNIX time-sharing system. Commun. ACM 17, 7 (July 1974), 365-375. DOI=10.1145/361011.361061
- 3. Linux • Linux (circa 1991) is a Unix-clone under FOSS • Comes in many flavours/distributions (distros): Linux kernel3 + GUI (optional) + application/software suite • bash (shell) + GCC + GDB + coreutils • 600+ distros • Popular ones: Ubuntu, Fedora, Debian, Gentoo, SUSE, etc. • Now being used atop desktops, servers, and mobile/embedded systems Linus Torvalds: comp.os.minix mailing list (1991-08-25) I’m doing a (free) operating system (just a hobby, won’t be big and professional like gnu) for 386(486) AT clones. 3 http://www.kernel.org/
- 4. Ubuntu • Built on top of Debian and developed/distributed by Canonical Ltd. • Most popular desktop/laptop distribution • Applications: LibreOffice, Firefox (web browser), Thunderbird (email/chat/news), Empathy (IM/VoIP), etc. • Variants: Ubuntu Deskop, Ubuntu Server, Ubuntu for Phones, etc.
- 5. Linux guide(s) • Introduction to Linux: A Hands on Guide; Achtelt Garrels; CreateSpace Independent Publishing Platform Available online: http://www.tldp.org/LDP/intro-linux/html/
- 6. Common commands Command ls cd file cat pwd man logout/exit Description List the contents of a directory Change directory (jump across the filesystem tree) Display file type Send file contents to standard output Display current working directory Display manual page Close the current session
- 7. Files Everything is a file On a UNIX system, everything is a file; if something is not a file, it is a process. Type Regular (-) Directory (d) Special (c) Links (l) Domain sockets (s) Named pipes (p) Block device files (b) Description Ordinary files To list other files Used for input/output Pointers to other files IPC through TCP/IP-like sockets IPC enablers To represent block devices
- 8. Partitioning • Divides the disk device into multiple logical storage units • Data partitions contain regular user data • Swap partitions house the swap space • Attached to the file system at mount points • df displays free disk space in active partitions
- 9. Filesystem layout Type /bin /boot /dev /etc /home /lib /lost+found /media /mnt /opt /proc Description Programs shared by users, administrators, and the system itself Start-up files Hardware devices Configuration files Home directories of users Library files for programs and the system Files saved in case of failure Mount point for removable media Mount point for external filesystems Third-party software Information about system resources (userspace window into kernel data structures)
- 10. Filesystem layout (2) /sbin /tmp /usr /var Programs shared by administrators and the system Temporary space User processes and libraries Files which change size regularly, e.g. log files, etc.
- 11. Paths, environment variables, and home directories • Two types of paths: 1 Relative: Relative to the current working directory • ∼: Relative to home directory 2 Absolute: Starting from the root directory • Environment variables: Contain dynamic values that change the behaviour of running programs, e.g. PATH, HOME, etc. • Each user has a home directory
- 12. Manipulating files/directories • Create directory: mkdir • Move file/directory: mv • Copy file/directory: cp • Remove file/directory: rm • Find file/directory: find <path> -name <filename>
- 13. Manipulating files and their contents • Filter results: grep • Invert: -v • Display values from the top: head • Display values from the bottom: tail • Display unique values: uniq • Change file permissions: chmod • Permissions: -, r, w, x (bit masks) • Permission categories: owner, group, everyone else • Count number of lines (-l), words (-w), and bytes(-c): wc
- 14. Pipes and input/output redirection • Pipe (|): Redirect standard output to standard input • Input/output redirection (<>): Redirect standard input or output to a file • Appending redirection: << or >> • Replacing a string in place: sed -i s/<original_string>/<new_string>/ <file> • Replacing a string and copying into a new file: sed s/<original_string>/<new_string>/ <input_file> > <output_file>
- 15. Shell scripts • Shell commands can be put into a file and executed as a script • A file can be made executable through chmod
- 16. Today’s Task • Write a bash script that: 1 2 3 4 5 Creates two folders in your home directory: 1) temp, and 2) results, Copies both dictionaries into temp and renames them to american-english-dictionary and british-english-dictionary, Counts the total number of lines in both dictionaries and stores them in count-british-english-dictionary and count-american-english-dictionary in the results folder, Stores unique American English words (not present in the British English dictionary) in unique-american-english and unique British English words (not present in the American English dictionary) in unique-british-english in the results folder, Stores common words (present in both dictionaries) in common-english in the results folder.