DOCSLIB.ORG

Advanced Bash-Scripting Guide

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Advanced Bash-Scripting Guide Advanced Bash−Scripting Guide An in−depth exploration of the art of shell scripting Mendel Cooper <[email protected]> 2.4 25 January 2004 Revision History Revision 2.1 14 September 2003 Revised by: mc 'HUCKLEBERRY' release: bugfixes and more material. Revision 2.2 31 October 2003 Revised by: mc 'CRANBERRY' release: Major update. Revision 2.3 03 January 2004 Revised by: mc 'STRAWBERRY' release: Major update. Revision 2.4 25 January 2004 Revised by: mc 'MUSKMELON' release: Bugfixes. This tutorial assumes no previous knowledge of scripting or programming, but progresses rapidly toward an intermediate/advanced level of instruction . all the while sneaking in little snippets of UNIX® wisdom and lore. It serves as a textbook, a manual for self−study, and a reference and source of knowledge on shell scripting techniques. The exercises and heavily−commented examples invite active reader participation, under the premise that the only way to really learn scripting is to write scripts. This book is suitable for classroom use as a general introduction to programming concepts. The latest update of this document, as an archived, bzip2−ed "tarball" including both the SGML source and rendered HTML, may be downloaded from the author's home site. See the change log for a revision history. Dedication For Anita, the source of all the magic Advanced Bash−Scripting Guide Table of Contents Chapter 1. Why Shell Programming?...............................................................................................................1 Chapter 2. Starting Off With a Sha−Bang.......................................................................................................3 2.1. Invoking the script............................................................................................................................5 2.2. Preliminary Exercises.......................................................................................................................5 Part 2. Basics.......................................................................................................................................................6 Chapter 3. Special Characters...........................................................................................................................7 Chapter 4. Introduction to Variables and Parameters..................................................................................23 4.1. Variable Substitution......................................................................................................................23 4.2. Variable Assignment.......................................................................................................................25 4.3. Bash Variables Are Untyped..........................................................................................................26 4.4. Special Variable Types...................................................................................................................28 Chapter 5. Quoting...........................................................................................................................................32 Chapter 6. Exit and Exit Status.......................................................................................................................38 Chapter 7. Tests................................................................................................................................................40 7.1. Test Constructs...............................................................................................................................40 7.2. File test operators............................................................................................................................46 7.3. Comparison operators (binary).......................................................................................................49 7.4. Nested if/then Condition Tests.......................................................................................................54 7.5. Testing Your Knowledge of Tests..................................................................................................54 Chapter 8. Operations and Related Topics....................................................................................................55 8.1. Operators.........................................................................................................................................55 8.2. Numerical Constants.......................................................................................................................61 Part 3. Beyond the Basics.................................................................................................................................63 Chapter 9. Variables Revisited........................................................................................................................64 9.1. Internal Variables............................................................................................................................64 9.2. Manipulating Strings.......................................................................................................................80 9.2.1. Manipulating strings using awk............................................................................................84 9.2.2. Further Discussion.................................................................................................................85 9.3. Parameter Substitution....................................................................................................................85 9.4. Typing variables: declare or typeset...............................................................................................93 9.5. Indirect References to Variables.....................................................................................................95 9.6. $RANDOM: generate random integer............................................................................................97 9.7. The Double Parentheses Construct...............................................................................................106 Chapter 10. Loops and Branches..................................................................................................................108 10.1. Loops..........................................................................................................................................108 10.2. Nested Loops..............................................................................................................................118 10.3. Loop Control...............................................................................................................................119 i Advanced Bash−Scripting Guide Table of Contents Chapter 10. Loops and Branches 10.4. Testing and Branching................................................................................................................122 Chapter 11. Internal Commands and Builtins.............................................................................................130 11.1. Job Control Commands..............................................................................................................151 Chapter 12. External Filters, Programs and Commands...........................................................................155 12.1. Basic Commands........................................................................................................................155 12.2. Complex Commands...................................................................................................................159 12.3. Time / Date Commands..............................................................................................................167 12.4. Text Processing Commands........................................................................................................169 12.5. File and Archiving Commands...................................................................................................186 12.6. Communications Commands......................................................................................................200 12.7. Terminal Control Commands.....................................................................................................204 12.8. Math Commands.........................................................................................................................205 12.9. Miscellaneous Commands..........................................................................................................214 Chapter 13. System and Administrative Commands..................................................................................224 Chapter 14. Command Substitution.............................................................................................................246 Chapter 15. Arithmetic Expansion................................................................................................................251 Chapter 16. I/O Redirection...........................................................................................................................252 16.1. Using exec...................................................................................................................................254 16.2. Redirecting Code Blocks............................................................................................................257 16.3. Applications................................................................................................................................261
Load more

Recommended publications
  • RACF Tips Volume 3, Issue 1, January 2009
    Volume 3 Issue 1 IPS RSH RACF T January For Administrators, Auditors, and Analysts 2009 Specifying a Replacement ID used to change a file's attributes for Program Control, APF Authorized, and Shared Library. with IRRRID00 . To generate commands to delete an ID and all references to it, use RACF's IRRRID00 utility. You simply enter the ID in the SYSIN DD Temporary Access with statement of the IRRRID00 job like so: CONNECT REVOKE(date) //SYSIN DD * USERX You may occasionally need to permit a user temporary access to a resource. One way to do If USERX is the owner of a profile or connect, so is to grant a group access to the resource IRRRID00 generates commands like: and connect the user to that group with a revoke date. The command to set the connect revoke CONNECT RDSADM GROUP(RACFSTC) OWNER(?USERX) date would look something like this: In these cases, you need to change ?USERX to CONNECT USERA GROUP(TEMPACC) REVOKE(1/20/09) a valid replacement ID. This can be done manually or with ISPF EDIT CHANGE. On the date specified with the revoke, RACF will no longer allow the user to have the access Alternatively, you can tell IRRRID00 which permitted to the group. If you want to remove the replacement ID to use when it builds the revoke date but leave the connect intact, enter: commands. If, for instance, you want to replace every occurrence of USERX with USERJ, enter CONNECT USERA GROUP(TEMPACC) NOREVOKE the following in the SYSIN DD: A banking client of ours used this capability to //SYSIN DD * govern access to APF-authorized libraries.
    [Show full text]
  • Introduction to Command Line and Accessing Servers Remotely
    Introduction to command line and accessing servers remotely Marco Büchler, Emily Franzini, Greta Franzini, Maria Moritz eTRAP Research Group Göttingen Centre for Digital Humanities Institute of Computer Science Georg August University Göttingen, Germany DH Estonia 2015 - Text Reuse Hackathon 20. Oktober 2015 Who am I? • 2001/2 Head of Quality Assurance department in a software company • 2006 Diploma in Computer Science on big • scale co-occurrence analysis • 2007- Consultant for several SMEs in IT sector • 2008 Technical project management of eAQUA project • 2011 PI and project manager of eTRACES project • 2013 PhD in „Digital Humanities“ on Text Reuse • 2014- Head of Early Career Research Group eTRAP at Göttingen Centre for Digital Humanities DH Estonia 2015 - Text Reuse Hackathon 20. Oktober 2015 Agenda 1) Connecting to the server 2) Some command line introduction DH Estonia 2015 - Text Reuse Hackathon 20. Oktober 2015 Connecting to the server 1) Windows: Start Putty 2) Mac + Linux: Open a terminal 3) Connecting to server via ssh -l <login> 192.168.11.4 4) Enter password DH Estonia 2015 - Text Reuse Hackathon 20. Oktober 2015 Which folder am I on the server? Command: pwd (parent working directory) Usage: pwd <ENTER> Example: pwd <ENTER> DH Estonia 2015 - Text Reuse Hackathon 20. Oktober 2015 Which files and directories are contained in my pwd? Command: ls (list) Usage: ls -l <FOLDER> <ENTER> // list all files and directory one on each line ls -la <FOLDER> <ENTER> // show also hidden files ls -lh <FOLDER> <ENTER> // show e.g. files sizes in human- friendly version Example: ls -l <ENTER> ls -lh /home/mbuechler <ENTER> DH Estonia 2015 - Text Reuse Hackathon 20.
    [Show full text]
  • LS-09EN. OS Permissions. SUID/SGID/Sticky. Extended Attributes
    Operating Systems LS-09. OS Permissions. SUID/SGID/Sticky. Extended Attributes. Operating System Concepts 1.1 ys©2019 Linux/UNIX Security Basics Agenda ! UID ! GID ! Superuser ! File Permissions ! Umask ! RUID/EUID, RGID/EGID ! SUID, SGID, Sticky bits ! File Extended Attributes ! Mount/umount ! Windows Permissions ! File Systems Restriction Operating System Concepts 1.2 ys©2019 Domain Implementation in Linux/UNIX ! Two types domain (subjects) groups ! User Domains = User ID (UID>0) or User Group ID (GID>0) ! Superuser Domains = Root ID (UID=0) or Root Group ID (root can do everything, GID=0) ! Domain switch accomplished via file system. ! Each file has associated with it a domain bit (SetUID bit = SUID bit). ! When file is executed and SUID=on, then Effective UID is set to Owner of the file being executed. When execution completes Efective UID is reset to Real UID. ! Each subject (process) and object (file, socket,etc) has a 16-bit UID. ! Each object also has a 16-bit GID and each subject has one or more GIDs. ! Objects have access control lists that specify read, write, and execute permissions for user, group, and world. Operating System Concepts 1.3 ys©2019 Subjects and Objects Subjects = processes Objects = files (regular, directory, (Effective UID, EGID) devices /dev, ram /proc) RUID (EUID) Owner permissions (UID) RGID-main (EGID) Group Owner permissions (GID) +RGID-list Others RUID, RGID Others ID permissions Operating System Concepts 1.4 ys©2019 The Superuser (root) • Almost every Unix system comes with a special user in the /etc/passwd file with a UID=0. This user is known as the superuser and is normally given the username root.
    [Show full text]
  • Shell Scripting with Bash
    Introduction to Shell Scripting with Bash Charles Jahnke Research Computing Services Information Services & Technology Topics for Today ● Introductions ● Basic Terminology ● How to get help ● Command-line vs. Scripting ● Variables ● Handling Arguments ● Standard I/O, Pipes, and Redirection ● Control Structures (loops and If statements) ● SCC Job Submission Example Research Computing Services Research Computing Services (RCS) A group within Information Services & Technology at Boston University provides computing, storage, and visualization resources and services to support research that has specialized or highly intensive computation, storage, bandwidth, or graphics requirements. Three Primary Services: ● Research Computation ● Research Visualization ● Research Consulting and Training Breadth of Research on the Shared Computing Cluster (SCC) Me ● Research Facilitator and Administrator ● Background in biomedical engineering, bioinformatics, and IT systems ● Offices on both CRC and BUMC ○ Most of our staff on the Charles River Campus, some dedicated to BUMC ● Contact: [email protected] You ● Who has experience programming? ● Using Linux? ● Using the Shared Computing Cluster (SCC)? Basic Terminology The Command-line The line on which commands are typed and passed to the shell. Username Hostname Current Directory [username@scc1 ~]$ Prompt Command Line (input) The Shell ● The interface between the user and the operating system ● Program that interprets and executes input ● Provides: ○ Built-in commands ○ Programming control structures ○ Environment
    [Show full text]
  • CST8207 – Linux O/S I
    Mounting a Filesystem Directory Structure Fstab Mount command CST8207 - Algonquin College 2 Chapter 12: page 467 - 496 CST8207 - Algonquin College 3 The mount utility connects filesystems to the Linux directory hierarchy. The mount point is a directory in the local filesystem where you can access mounted filesystem. This directory must exist before you can mount a filesystem. All filesystems visible on the system exist as a mounted filesystem someplace below the root (/) directory CST8207 - Algonquin College 4 can be mounted manually ◦ can be listed in /etc/fstab, but not necessary ◦ all mounting information supplied manually at command line by user or administrator can be mounted automatically on startup ◦ must be listed /etc/fstab, with all appropriate information and options required Every filesystem, drive, storage device is listed as a mounted filesystem associated to a directory someplace under the root (/) directory CST8207 - Algonquin College 5 CST8207 - Algonquin College 6 Benefits Scalable ◦ As new drives are added and new partitions are created, further filesystems can be mounted at various mount points as required. ◦ This means a Linux system does not need to worry about running out of disk space. Transparent ◦ No application would stop working if transferred to a different partition, because access to data is done via the mount point. ◦ Also transparent to user CST8207 - Algonquin College 7 All known filesystems volumes are typically listed in the /etc/fstab (static information about filesystem) file to help automate the mounting process If it is not listed in the /etc/fstab file, then all appropriate information about the filesystem needs to be listed manually at the command line.
    [Show full text]
  • Download the Specification
    Internationalizing and Localizing Applications in Oracle Solaris Part No: E61053 November 2020 Internationalizing and Localizing Applications in Oracle Solaris Part No: E61053 Copyright © 2014, 2020, Oracle and/or its affiliates. License Restrictions Warranty/Consequential Damages Disclaimer This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited. Warranty Disclaimer The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing. Restricted Rights Notice If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, then the following notice is applicable: U.S. GOVERNMENT END USERS: Oracle programs (including any operating system, integrated software, any programs embedded, installed or activated on delivered hardware, and modifications of such programs) and Oracle computer documentation or other Oracle data delivered to or accessed by U.S. Government end users are "commercial
    [Show full text]
  • A Brief History of UNIX File Systems
    A Brief History of UNIX File Systems Val Henson IBM, Inc. [email protected] Summary • Review of UNIX file system concepts • File system formats, 1974-2004 • File system comparisons and recommendations • Fun trivia • Questions and answers (corrections ONLY during talk) 1 VFS/vnode architecture • VFS: Virtual File System: common object-oriented interface to fs's • vnode: virtual node: abstract file object, includes vnode ops • All operations to fs's and files done through VFS/vnode in- terface • S.R. Kleiman, \Vnodes: An Architecture for Multiple File System Types in Sun UNIX," Summer USENIX 1986 2 Some Definitions superblock: fs summary, pointers to other information inode: on-disk structure containing information about a file indirect block: block containing pointers to other blocks metadata: everything that is not user data, including directory entries 3 Disk characteristics • Track - contiguous region, can be read at maximum speed • Seek time - time to move the head between different tracks • Rotational delay - time for part of track to move under head • Fixed per I/O overhead means bigger I/Os are better 4 In the beginning: System V FS (S5FS) (c. 1974) • First UNIX file system, referred to as \FS" • Disk layout: superblock, inodes, followed by everything else • 512-1024 byte block size, no fragments • Super simple - and super slow! 2-5% of raw disk bandwidth 5 Berkeley Fast File System (FFS or UFS) (c. 1984) • Metadata spread throughout the disk in \cylinder groups" • Block size 4KB minimum, frag size 1KB (to avoid 45% wasted space) • Physical
    [Show full text]
  • Beginning Portable Shell Scripting from Novice to Professional
    Beginning Portable Shell Scripting From Novice to Professional Peter Seebach 10436fmfinal 1 10/23/08 10:40:24 PM Beginning Portable Shell Scripting: From Novice to Professional Copyright © 2008 by Peter Seebach All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. ISBN-13 (pbk): 978-1-4302-1043-6 ISBN-10 (pbk): 1-4302-1043-5 ISBN-13 (electronic): 978-1-4302-1044-3 ISBN-10 (electronic): 1-4302-1044-3 Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1 Trademarked names may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, we use the names only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. Lead Editor: Frank Pohlmann Technical Reviewer: Gary V. Vaughan Editorial Board: Clay Andres, Steve Anglin, Ewan Buckingham, Tony Campbell, Gary Cornell, Jonathan Gennick, Michelle Lowman, Matthew Moodie, Jeffrey Pepper, Frank Pohlmann, Ben Renow-Clarke, Dominic Shakeshaft, Matt Wade, Tom Welsh Project Manager: Richard Dal Porto Copy Editor: Kim Benbow Associate Production Director: Kari Brooks-Copony Production Editor: Katie Stence Compositor: Linda Weidemann, Wolf Creek Press Proofreader: Dan Shaw Indexer: Broccoli Information Management Cover Designer: Kurt Krames Manufacturing Director: Tom Debolski Distributed to the book trade worldwide by Springer-Verlag New York, Inc., 233 Spring Street, 6th Floor, New York, NY 10013.
    [Show full text]
  • File System, Files, and *Tab /Etc/Fstab
    File system, files, and *tab File system files directories volumes, file systems mounting points local versus networked file systems 1 /etc/fstab Specifies what is to be mounted where and how fs_spec: describes block special device for remote filesystem to be mounted fs_file: describes the mount point fs_vfstype: describes the type of file system fs_mntops: describes the mount options associated with the filesystem 2 /etc/fstab cont. fs_freq: used by the dump command fs_passno: used by fsck to determine the order in which checks are done at boot time. Root file systems should be specified as 1, others should be 2. Value 0 means that file system does not need to be checked 3 /etc/fstab 4 from blocks to mounting points metadata inodes directories superblocks 5 mounting file systems mounting e.g., mount -a unmounting manually or during shutdown umount 6 /etc/mtab see what is mounted 7 Network File System Access file system (FS) over a network looks like a local file system to user e.g. mount user FS rather than duplicating it (which would be a disaster) Developed by Sun Microsystems (mid 80s) history for NFS: NFS, NFSv2, NFSv3, NFSv4 RFC 3530 (from 2003) take a look to see what these RFCs are like!) 8 Network File System How does this actually work? server needs to export the system client needs to mount the system server: /etc/exports file client: /etc/fstab file 9 Network File System Security concerns UID GID What problems could arise? 10 Network File System example from our raid system (what is a RAID again?) Example of exports file from
    [Show full text]
  • Introduction to Unix
    Introduction to Unix Rob Funk <[email protected]> University Technology Services Workstation Support http://wks.uts.ohio-state.edu/ University Technology Services Course Objectives • basic background in Unix structure • knowledge of getting started • directory navigation and control • file maintenance and display commands • shells • Unix features • text processing University Technology Services Course Objectives Useful commands • working with files • system resources • printing • vi editor University Technology Services In the Introduction to UNIX document 3 • shell programming • Unix command summary tables • short Unix bibliography (also see web site) We will not, however, be covering these topics in the lecture. Numbers on slides indicate page number in book. University Technology Services History of Unix 7–8 1960s multics project (MIT, GE, AT&T) 1970s AT&T Bell Labs 1970s/80s UC Berkeley 1980s DOS imitated many Unix ideas Commercial Unix fragmentation GNU Project 1990s Linux now Unix is widespread and available from many sources, both free and commercial University Technology Services Unix Systems 7–8 SunOS/Solaris Sun Microsystems Digital Unix (Tru64) Digital/Compaq HP-UX Hewlett Packard Irix SGI UNICOS Cray NetBSD, FreeBSD UC Berkeley / the Net Linux Linus Torvalds / the Net University Technology Services Unix Philosophy • Multiuser / Multitasking • Toolbox approach • Flexibility / Freedom • Conciseness • Everything is a file • File system has places, processes have life • Designed by programmers for programmers University Technology Services
    [Show full text]
  • Use Perl Regular Expressions in SAS® Shuguang Zhang, WRDS, Philadelphia, PA
    NESUG 2007 Programming Beyond the Basics Use Perl Regular Expressions in SAS® Shuguang Zhang, WRDS, Philadelphia, PA ABSTRACT Regular Expression (Regexp) enhance search and replace operations on text. In SAS®, the INDEX, SCAN and SUBSTR functions along with concatenation (||) can be used for simple search and replace operations on static text. These functions lack flexibility and make searching dynamic text difficult, and involve more function calls. Regexp combines most, if not all, of these steps into one expression. This makes code less error prone, easier to maintain, clearer, and can improve performance. This paper will discuss three ways to use Perl Regular Expression in SAS: 1. Use SAS PRX functions; 2. Use Perl Regular Expression with filename statement through a PIPE such as ‘Filename fileref PIPE 'Perl programm'; 3. Use an X command such as ‘X Perl_program’; Three typical uses of regular expressions will also be discussed and example(s) will be presented for each: 1. Test for a pattern of characters within a string; 2. Replace text; 3. Extract a substring. INTRODUCTION Perl is short for “Practical Extraction and Report Language". Larry Wall Created Perl in mid-1980s when he was trying to produce some reports from a Usenet-Nes-like hierarchy of files. Perl tries to fill the gap between low-level programming and high-level programming and it is easy, nearly unlimited, and fast. A regular expression, often called a pattern in Perl, is a template that either matches or does not match a given string. That is, there are an infinite number of possible text strings.
    [Show full text]
  • A First Course to Openfoam
    Basic Shell Scripting Slides from Wei Feinstein HPC User Services LSU HPC & LON [email protected] September 2018 Outline • Introduction to Linux Shell • Shell Scripting Basics • Variables/Special Characters • Arithmetic Operations • Arrays • Beyond Basic Shell Scripting – Flow Control – Functions • Advanced Text Processing Commands (grep, sed, awk) Basic Shell Scripting 2 Linux System Architecture Basic Shell Scripting 3 Linux Shell What is a Shell ▪ An application running on top of the kernel and provides a command line interface to the system ▪ Process user’s commands, gather input from user and execute programs ▪ Types of shell with varied features o sh o csh o ksh o bash o tcsh Basic Shell Scripting 4 Shell Comparison Software sh csh ksh bash tcsh Programming language y y y y y Shell variables y y y y y Command alias n y y y y Command history n y y y y Filename autocompletion n y* y* y y Command line editing n n y* y y Job control n y y y y *: not by default http://www.cis.rit.edu/class/simg211/unixintro/Shell.html Basic Shell Scripting 5 What can you do with a shell? ▪ Check the current shell ▪ echo $SHELL ▪ List available shells on the system ▪ cat /etc/shells ▪ Change to another shell ▪ csh ▪ Date ▪ date ▪ wget: get online files ▪ wget https://ftp.gnu.org/gnu/gcc/gcc-7.1.0/gcc-7.1.0.tar.gz ▪ Compile and run applications ▪ gcc hello.c –o hello ▪ ./hello ▪ What we need to learn today? o Automation of an entire script of commands! o Use the shell script to run jobs – Write job scripts Basic Shell Scripting 6 Shell Scripting ▪ Script: a program written for a software environment to automate execution of tasks ▪ A series of shell commands put together in a file ▪ When the script is executed, those commands will be executed one line at a time automatically ▪ Shell script is interpreted, not compiled.
    [Show full text]