Bash-Beginners-Guide

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Bash Guide for Beginners 9.2.2. Examples 9.2.2.1. Simple example using while Here is an example for the impatient: #!/bin/bash # This script opens 4 terminal windows. i="0" while [ $i -lt 4 ] do xterm & i=$[$i+1] done 9.2.2.2. Nested while loops The example below was written to copy pictures that are made with a webcam to a web directory. Every five minutes a picture is taken. Every hour, a new directory is created, holding the images for that hour. Every day, a new directory is created containing 24 subdirectories. The script runs in the background. #!/bin/bash # This script copies files from my homedirectory into the webserver directory. # (use scp and SSH keys for a remote directory) # A new directory is created every hour. PICSDIR=/home/carol/pics WEBDIR=/var/www/carol/webcam while true; do DATE=`date +%Y%m%d` HOUR=`date +%H` mkdir $WEBDIR/"$DATE" while [ $HOUR -ne "00" ]; do DESTDIR=$WEBDIR/"$DATE"/"$HOUR" mkdir "$DESTDIR" mv $PICDIR/*.jpg "$DESTDIR"/ sleep 3600 HOUR=`date +%H` done done Note the use of the true statement. This means: continue execution until we are forcibly interrupted (with kill or Ctrl+C). This small script can be used for simulation testing; it generates files: #!/bin/bash # This generates a file every 5 minutes while true; do Chapter 9. Repetitive tasks 110
touch pic-`date +%s`.jpg sleep 300 done Note the use of the date command to generate all kinds of file and directory names. See the man page for more. Use the system Bash Guide for Beginners The previous example is for the sake of demonstration. Regular checks can easily be achieved using the system's cron facility. Do not forget to redirect output and errors when using scripts that are executed from your crontab! 9.2.2.3. Using keyboard input to control the while loop This script can be interrupted by the user when a Ctrl+C sequence is entered: #!/bin/bash # This script provides wisdom FORTUNE=/usr/games/fortune while true; do echo "On which topic do you want advice?" cat
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Bash Guide for Beginners Machtelt G
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Bash Guide for Beginners Table of C
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Bash Guide for Beginners Table of C
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Table of Contents Glossary C.......
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Introduction 1. Why this guide? The
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Revision 1.6 2005-03-01 Revised by:
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Bash Guide for Beginners See Chapte
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Bash Guide for Beginners mia:~> cat
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Bash Guide for Beginners When invok
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More information about the file des
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Built-in commands are necessary to
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• Brace expansion • Tilde expan
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A number of methods can be used; on
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Bash Guide for Beginners stop in ea
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Chapter 2. Writing and debugging sc
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the documentation of your favorite
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Bash Guide for Beginners Comments a
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Bash Guide for Beginners + set +x I
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Chapter 3. The Bash environment In
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Bash Guide for Beginners local pid
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MOZILLA_FIVE_HOME=/usr/lib/mozilla
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Bash Guide for Beginners franky ~>
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the GNU Awk programming language is
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Bash Guide for Beginners 3.2.4. Res
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LINES MACHTYPE MAILCHECK OLDPWD OPT
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two is the second positional parame
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Bash Guide for Beginners 3.3.1. Why
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A correctly-formed brace expansion
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Bash Guide for Beginners If the sub
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of the whitespace characters "space
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Bash Guide for Beginners /dev/hda5
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Bash Guide for Beginners 3.7. Summa
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Two regular expressions may be conc
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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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