Bash-Beginners-Guide

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1.2.2.2.1. Invoked as an interactive login shell, or with `--login' Interactive means you can enter commands. The shell is not running because a script has been activated. A login shell means that you got the shell after authenticating to the system, usually by giving your user name and password. Files read: Bash Guide for Beginners • /etc/profile • ~/.bash_profile, ~/.bash_login or ~/.profile: first existing readable file is read • ~/.bash_logout upon logout. Error messages are printed if configuration files exist but are not readable. If a file does not exist, bash searches for the next. 1.2.2.2.2. Invoked as an interactive non-login shell A non-login shell means that you did not have to authenticate to the system. For instance, when you open a terminal using an icon, or a menu item, that is a non-login shell. Files read: • ~/.bashrc This file is usually referred to in ~/.bash_profile: if [ -f ~/.bashrc ]; then . ~/.bashrc; fi See Chapter 7 for more information on the if construct. 1.2.2.2.3. Invoked non-interactively All scripts use non-interactive shells. They are programmed to do certain tasks and cannot be instructed to do other jobs than those for which they are programmed. Files read: • defined by BASH_ENV PATH is not used to search for this file, so if you want to use it, best refer to it by giving the full path and file name. 1.2.2.2.4. Invoked with the sh command Bash tries to behave as the historical Bourne sh program while conforming to the POSIX standard as well. Files read: • /etc/profile • ~/.profile Chapter 1. Bash and Bash scripts 8
Bash Guide for Beginners When invoked interactively, the ENV variable can point to extra startup information. 1.2.2.2.5. POSIX mode This option is enabled either using the set built-in: set -o posix or by calling the bash program with the --posix option. Bash will then try to behave as compliant as possible to the POSIX standard for shells. Setting the POSIXLY_CORRECT variable does the same. Files read: • defined by ENV variable. 1.2.2.2.6. Invoked remotely Files read when invoked by rshd: • ~/.bashrc Avoid use of r-tools Be aware of the dangers when using tools such as rlogin, telnet, rsh and rcp. They are intrinsically insecure because confidential data is sent over the network unencrypted. If you need tools for remote execution, file transfer and so on, use an implementation of Secure SHell, generally known as SSH, freely available from http://www.openssh.org. Different client programs are available for non-UNIX systems as well, see your local software mirror. 1.2.2.2.7. Invoked when UID is not equal to EUID No startup files are read in this case. 1.2.2.3. Interactive shells 1.2.2.3.1. What is an interactive shell? An interactive shell generally reads from, and writes to, a user's terminal: input and output are connected to a terminal. Bash interactive behavior is started when the bash command is called upon without non-option arguments, except when the option is a string to read from or when the shell is invoked to read from standard input, which allows for positional parameters to be set (see Chapter 3 ). 1.2.2.3.2. Is this shell interactive? Test by looking at the content of the special parameter -, it contains an 'i' when the shell is interactive: eddy:~> echo $- himBH In non-interactive shells, the prompt, PS1, is unset. Chapter 1. Bash and Bash scripts 9
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LABEL=/ / ext3 defaults 1 1 If this
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cathy ~> ls -ld [[:digit:]]* drwxrw
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Bash Guide for Beginners p Print te
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sandy ~> sed -n '/a text/,/This/p'
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Bash Guide for Beginners # This is
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Chapter 6. The GNU awk programming
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Bash Guide for Beginners 121script.
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Bash Guide for Beginners amd.conf a
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Bash Guide for Beginners record1 re
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Bash Guide for Beginners 6.3.6. The
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Chapter 7. Conditional statements I
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Bash Guide for Beginners Table 7-2.
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Bash Guide for Beginners 7.1.2.2. N
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[root@elegance root]# We switch to
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Bash Guide for Beginners echo "Prop
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Bash Guide for Beginners We use the
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Bash Guide for Beginners case EXPRE
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Upon successful condition testing,
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Bash Guide for Beginners bit better
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8.2. Catching user input 8.2.1. Usi
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Bash Guide for Beginners michel ~/t
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Bash Guide for Beginners # DO NOT E
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File descriptor 5 Bash Guide for Be
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Bash Guide for Beginners The result
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Bash Guide for Beginners ♦ Compre
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Bash Guide for Beginners for i in `
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touch pic-`date +%s`.jpg sleep 300
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DISKFUL=$(df -h $WEBDIR | grep -v F
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;; 2) $FORTUNE startrek ;; 3) $FORT
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[carol@octarine ~/test] ls -a ./ ..
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Bash Guide for Beginners 9.7.2. Exa
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Chapter 10. More on variables In th
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Bash Guide for Beginners [bob in ~]
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if [ -z $1 ]; then echo "Usage: $0
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10.3.3. Transformations of variable
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Bash Guide for Beginners The opposi
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Chapter 11. Functions In this chapt
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The commands after && are only exec
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zip2 "$TAR" echo "...done." >> "$LO
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Chapter 12. Catching signals In thi
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Bash Guide for Beginners maud: ~> k
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Bash Guide for Beginners 2. Write a
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Bash Guide for Beginners jobs kill
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if [ $i -eq 5 ] ArrowUp+Enter or !!
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cd Change directory. cdp/cdplay An
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Bash Guide for Beginners gimp grep
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Send and receive mail. man Read man
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Bash Guide for Beginners rsh RPM Pa
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W Bash Guide for Beginners w Show w
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Index A aliases Section 3.5.1 ANSI-
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Bash Guide for Beginners Section 3.
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J Bash Guide for Beginners K kill k
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eadonly Section 10.1.3 regular expr
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Bash Guide for Beginners vi(m) Sect
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