Advanced Bash−Scripting Guide

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Advanced Bash−Scripting Guide bash$ lsdev Device DMA IRQ I/O Ports −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− cascade 4 2 dma 0080−008f dma1 0000−001f dma2 00c0−00df fpu 00f0−00ff ide0 14 01f0−01f7 03f6−03f6 ... du df stat Show (disk) file usage, recursively. Defaults to current working directory, unless otherwise specified. bash$ du −ach 1.0k ./wi.sh 1.0k ./tst.sh 1.0k ./random.file 6.0k . 6.0k total Shows filesystem usage in tabular form. bash$ df Filesystem 1k−blocks Used Available Use% Mounted on /dev/hda5 273262 92607 166547 36% / /dev/hda8 222525 123951 87085 59% /home /dev/hda7 1408796 1075744 261488 80% /usr Gives detailed and verbose statistics on a given file (even a directory or device file) or set of files. bash$ stat test.cru File: "test.cru" Size: 49970 Allocated Blocks: 100 Filetype: Regular File Mode: (0664/−rw−rw−r−−) Uid: ( 501/ bozo) Gid: ( 501/ bozo) Device: 3,8 Inode: 18185 Links: 1 Access: Sat Jun 2 16:40:24 2001 Modify: Sat Jun 2 16:40:24 2001 Change: Sat Jun 2 16:40:24 2001 If the target file does not exist, stat returns an error message. bash$ stat nonexistent−file nonexistent−file: No such file or directory vmstat Display virtual memory statistics. bash$ vmstat procs memory swap io system cpu r b w swpd free buff cache si so bi bo in cs us sy id 0 0 0 0 11040 2636 38952 0 0 33 7 271 88 8 3 89 netstat Show current network statistics and information, such as routing tables and active connections. This utility accesses information in /proc/net (Chapter 28). See Example 28−2. Chapter 13. System and Administrative Commands 222
Advanced Bash−Scripting Guide netstat −r is equivalent to route. uptime Shows how long the system has been running, along with associated statistics. bash$ uptime 10:28pm up 1:57, 3 users, load average: 0.17, 0.34, 0.27 hostname Lists the system's host name. This command sets the host name in an /etc/rc.d setup script (/etc/rc.d/rc.sysinit or similar). It is equivalent to uname −n, and a counterpart to the $HOSTNAME internal variable. bash$ hostname localhost.localdomain hostid bash$ echo $HOSTNAME localhost.localdomain Echo a 32−bit hexadecimal numerical identifier for the host machine. bash$ hostid 7f0100 This command allegedly fetches a "unique" serial number for a particular system. Certain product registration procedures use this number to brand a particular user license. Unfortunately, hostid only returns the machine network address in hexadecimal, with pairs of bytes transposed. The network address of a typical non−networked Linux machine, is found in /etc/hosts. bash$ cat /etc/hosts 127.0.0.1 localhost.localdomain localhost sar As it happens, transposing the bytes of 127.0.0.1, we get 0.127.1.0, which translates in hex to 007f0100, the exact equivalent of what hostid returns, above. There exist only a few million other Linux machines with this identical hostid. Invoking sar (system activity report) gives a very detailed rundown on system statistics. This command is found on some commercial UNIX systems, but is not part of the base Linux distribution. It is contained in the sysstat utilities package, written by Sebastien Godard. bash$ sar Linux 2.4.7−10 (localhost.localdomain) 12/31/2001 10:30:01 AM CPU %user %nice %system %idle 10:40:00 AM all 1.39 0.00 0.77 97.84 10:50:00 AM all 76.83 0.00 1.45 21.72 11:00:00 AM all 1.32 0.00 0.69 97.99 11:10:00 AM all 1.17 0.00 0.30 98.53 11:20:00 AM all 0.51 0.00 0.30 99.19 06:30:00 PM all 100.00 0.00 100.01 0.00 Average: all 1.39 0.00 0.66 97.95 readelf Chapter 13. System and Administrative Commands 223
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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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Chapter 3. Special Characters Speci
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# Sometimes, though, you get: # 11
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The "−" can be used to pipe stdou
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change the behavior of the terminal
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Chapter 4. Introduction to Variable
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The shift command reassigns the pos
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Example 5−1. Echoing Weird Variab
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(cd /source/directory && tar cf −
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true # the "true" builtin. echo "ex
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if [[ −e $file ]] then echo "Pass
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7.3. Comparison operators (binary)
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Example 7−5. arithmetic and strin
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Chapter 8. Operations and Related T
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Part 3. Beyond the Basics Table of
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$EDITOR the default editor invoked
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Example 9−2. Timed Input Advanced
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echo 'IFS=":", using "$@"' c=0 for
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echo '${var1#$pattern1} =' "${var1#
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t=${path_name%/*.*} # Same effect a
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Chapter 10. Loops and Branches Oper
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Advanced Bash−Scripting Guide OUT
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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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Page 177 and 178: The −d option deletes a range of
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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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Advanced Bash−Scripting Guide # A
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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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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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Advanced Bash−Scripting Guide # I
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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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