Advanced Bash−Scripting Guide

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Advanced Bash−Scripting Guide A−7). It can even be used to generate prime numbers, (see Example A−17). Modulo turns up surprisingly often in various numerical recipes. Example 8−1. Greatest common divisor #!/bin/bash # gcd.sh: greatest common divisor # Uses Euclid's algorithm # The "greatest common divisor" (gcd) of two integers #+ is the largest integer that will divide both, leaving no remainder. # Euclid's algorithm uses successive division. # In each pass, #+ dividend
Advanced Bash−Scripting Guide echo; echo "GCD of $1 and $2 = $dividend"; echo # Exercise : # −−−−−−−− # Check command−line arguments to make sure they are integers, #+ and exit the script with an appropriate error message if not. += −= *= /= %= exit 0 "plus−equal" (increment variable by a constant) let "var += 5" results in var being incremented by 5. "minus−equal" (decrement variable by a constant) "times−equal" (multiply variable by a constant) let "var *= 4" results in var being multiplied by 4. "slash−equal" (divide variable by a constant) "mod−equal" (remainder of dividing variable by a constant) Arithmetic operators often occur in an expr or let expression. Example 8−2. Using Arithmetic Operations #!/bin/bash # Counting to 6 in 5 different ways. n=1; echo −n "$n " let "n = $n + 1" # let "n = n + 1" also works. echo −n "$n " : $((n = $n + 1)) # ":" necessary because otherwise Bash attempts #+ to interpret "$((n = $n + 1))" as a command. echo −n "$n " n=$(($n + 1)) echo −n "$n " : $[ n = $n + 1 ] # ":" necessary because otherwise Bash attempts #+ to interpret "$[ n = $n + 1 ]" as a command. # Works even if "n" was initialized as a string. echo −n "$n " n=$[ $n + 1 ] # Works even if "n" was initialized as a string. #* Avoid this type of construct, since it is obsolete and nonportable. echo −n "$n "; echo # Thanks, Stephane Chazelas. Chapter 8. Operations and Related Topics 57
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Chapter 1. Why Shell Programming? A
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Chapter 2. Starting Off With a Sha
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As is the case with for/in loops, p
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This construct tests for a conditio
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# Accept upper or lowercase input.
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# May need to also press ENTER if a
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cat, tac # Burn the CDR. cdrecord
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Advanced Bash−Scripting Guide 12.
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exit $E_CHANGED_MIND ;; *) echo "De
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The multiplication operator must be
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echo Number of digits at the beginn
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Outputs very verbose timing statist
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This line occurs three times. This
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# List all the users in /etc/passwd
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Advanced Bash−Scripting Guide # r
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Advanced Bash−Scripting Guide gre
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The −d option deletes a range of
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# Delete CR and write to new file.
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mailto Similar to the mail command,
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[ ${NETWORKING} = "no" ] && exit 0
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chroot Advanced Bash−Scripting Gu
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Chapter 15. Arithmetic Expansion Ar
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# Saves stdin. Advanced Bash−Scri
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Chapter 17. Here Documents A here d
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Example 17−11. A self−documenti
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Part 4. Advanced Topics At this poi
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"Sed & Awk", by Dougherty and Robbi
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Chapter 20. Subshells Running a she
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# Range: 0 − 200 # It's crude, bu
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# grep PATTERN /etc/passwd | awk
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Advanced Bash−Scripting Guide # Y
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Chapter 25. List Constructs The "an
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# AND LIST executes on true, OR LIS
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echo ${colors[$index]} let "index =
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# Replace all matching wildcarded s
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fi let "t += $i " Primes[t]=$NON_PR
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# −−−−−−−−− # 1)
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Chapter 28. /dev and /proc A Linux
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Chapter 30. Debugging The Bash shel
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4. Advanced Bash−Scripting Guide
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Chapter 31. Options Options are set
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Chapter 32. Gotchas Turandot: Gli e
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command1 2> − | command2 # Trying
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echo "one two three" | read a b c #
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Chapter 33. Scripting With Style Ge
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#!/bin/bash # color−echo.sh: Echo
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34.7. Assorted Tips Advanced Bash
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# agram.sh: Playing games with anag
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Chapter 35. Bash, version 2 The cur
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1−56592−580−7). This is the s
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Bibliography Edited by Peter Dennin
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Advanced Bash−Scripting Guide * A
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Mark Komarinski's Printing−Usage
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let "row = $r" # Count center row o
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next_gen "$Cur" let "generation +=
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[−c localdirectory] [−m filepat
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Advanced Bash−Scripting Guide #:d
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# ListDirectory "FileGlob" "Field
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The md5sum program is documented as
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Note: 'mount −l' does return the
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Appendix B. A Sed and Awk Micro−P
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Appendix D. A Detailed Introduction
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Appendix E. Localization Localizati
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Appendix F. History Commands The Ba
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Appendix H. Converting DOS Batch Fi
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Appendix I. Exercises I.1. Analyzin
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Lottery Numbers One type of lottery
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[33] This is actually a script adap
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# Thanks to Stephane Chazelas for p
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