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RELEASE HISTORY
------- -------
Version 0.4, released 07/09/01
Comments: Complete revision. The document is now the equivalent of a
300-page book.
Changes from version 0.3:
1) Substituted Emmanuel Rouat's new, improved Linux-specific .bashrc
file for the old one.
2)
In "External Filters, Programs, and Commands" section:
More info on "sleep".
Added "usleep".
More info on "diff", with note about using it to recursively compare
directories.
Added "diff3".
Added "sdiff".
Added "cmp".
Added example using "cmp", and cross referenced it to "exit status".
Added "hwclock/clock".
Added "locate/slocate".
Added "whatis", with example script.
Added "whereis".
Added "od".
Added "unexpand".
Added "install".
Added "crypt".
Added "write".
Added "compress/uncompress".
Added "gettext".
Added "printenv".
Added "tput".
More info on "fold" (-s option).
More info on "patch".
More info on "join".
More info on "tar".
More info on "tr".
More info on "dd".
More info on "logger".
More options for "cat".
More options for "cp".
Added cautionary note to "tar".
Added --count and --invert-match options to "grep".
Extra options and code snippets for "find".
Using "echo" to feed a command sequence into a pipe and set a variable,
with illustrative code snippets.
Added subsection for "Terminal Control Commands" (tput, clear, reset,
script).
Added subsection for "Math Commands" (factor, bc/dc).
3) Moved subsection on "Here Documents" to right after "I/O Redirection" (much
more logical).
4) Added more reasons not to use shell scripts.
5) Added info about the "widtools" (widget tools) package to "Assorted Tips"
subsection of "Miscellany".
6) Corrected "Born-Again Shell" to "Bourne-Again Shell" (thanks to Jan
Svenungson for pointing this out).
7) In "System and Administrative Commands" section:
Added "dumpe2fs".
Added "tune2fs".
Added "fdisk".
Added "mke2fs".
Added "fsck", "e2fsck", and "debugfs".
Added script using "fdisk" and "mke2fs".
Added "df".
Added "du".
Added "mesg".
Added tip.
Added "procinfo".
Added "ac"
Added "last"
Added "tset"
Added "getty" and "agetty".
Added "chown/chgrp".
Added "useradd/userdel".
Added "logrotate".
Added "dump/restore".
Added "stat".
Added "rdist".
Added "losetup".
Added "lastcomm".
Added "mkswap".
Added "swapon/swapoff".
Added "newgrp".
More info on "chroot".
More info on "netstat".
More info on "ifconfig".
More info on "route".
More info and example added on "mount".
Added note to "umount".
Usage example on "lsmod".
Removed inappropriate spacing in "wall" listing and added note.
8) In "Internal Commands" section:
Added "pstree".
Added "type".
Added "help".
Added footnote on "forking".
More info on "kill".
Added example to "unset".
More options and info added to "read".
9) Additional clarification of "for" loops.
10) Added using C-like syntax in a "for" loop to "Loops" section,
with illustrative example.
Did the same with a "while" loop.
Cross-references to examples in "Miscellany / Assorted Tips" section.
11) Added using command substitution to generate [list] in a "for" loop.
Same for a "case" construct.
Examples added.
12) In "Variables Revisited" section, added C-type variable manipulation,
using the ((...)) construct [Chet Ramey's Easter Egg, actually borrowed
from ksh93].
13) In "Gotchas" section,
Added scripts with DOS-type newlines.
Added script invoked with "/bin/sh" maybe not fully Bash-compatible.
14) In "Files" section, added ~/.bash_logout.
15) In "Variables Revisited" section,
Moved note about certain variables not internal to Bash to a more logical location.
Added short note about using /dev/urandom to generate (useless) random numbers.
Added $LINENO to internal variables.
Added illustrative script ("am-i-root.sh") to "UID" discussion.
Fixed "dubugging" typo.
16) In "Bibliography" section,
Added four sites for example shell scripts.
Added reference to Rick Hohensee's shell-scripted virtual machine + assembler.
17) Added "mail-format.sh" to "Contributed Scripts" section.
18) In "Tests" section:
Clearer definition of what "test" actually means.
Add info about "-g", "-u", and "-k" flags.
Clarified examples of "integer tests" (used if [ "$a" XX "$b" ] to illustrate).
19) Fixed syntax error in "ex45.sh" (embarrassing).
20) Added piping the output of a "for" loop to a command.
21) Mention /usr/include/sysexits.h as an attempt at systematizing exit status
numbers.
22) Added "string.sh", a "Contrib Script" by Noah Friedman.
23) Alphabetized listing of internal Bash variables in "Variables Revisited"
section. It looks more professional now.
24) Added subsection on "Nested Loops" to "Loops" section.
Added illustrative example script.
25) Added subsection on "Nested if/then Condition Tests" to "Tests" section.
26) In "Here Documents" section,
Added - option.
Added passing parameters to body of here document, with examples.
Added disabling parameter replacement by quoting or escaping.
27) In "Special Characters" section,
Added info on "-" redirection operator.
Added quotes ("").
Added strong quotes ('').
Added escape (\).
Added backticks (`).
Added using ":" for comment line (not recommended).
Added "*".
Added "$*" and "$@".
Piping the output of command(s) to a script.
More info on "!" operator.
Annotated Alan Cox's one-liner script.
Added "_" (underscore).
28) Reorganized "Loops" section; created new subsection and reshuffled.
29) Added instance of "unset" to when a variable appears "naked" (without the
$ prefix). Thanks to Florian Wisser for pointing this out.
30) Rewrote "Command Substitution" section (formerly named "Backticks").
Split off "Arithmetic Expansion" as a separate section, and added
material.
31) Added "bc" and "dc" to "External Filters" section, with elegant
illustrative script by Heiner Steven.
Added more info on "bc", with "monthlypmt.sh" illustrative example.
32) Added new section on "/dev and /proc".
Added illustrative examples.
33) Made a number of corrections and clarifications, as pointed out by Heiner
Steven. Thanks!
Some UNIX flavors take a 4-byte magic number...
Too many script headers on one line in "magic number" example listing.
Example "ex2.sh", added comment that "> filename" is equivalent to "cat /dev/null > filename".
Example "ex2.sh", quoted parameter.
Omitting [list] in a "for" loop assumes "$@", rather than "$*".
Clarified that a "flag" acts as a semaphore, rather than as a signal.
Added comment that {code block} does not launch a subshell to
"Special Characters" section.
At his suggestion, added a couple of more examples on "~" in
"Special Characters" section.
Added his "allprofs" script to "Subshells" section (with modifications
by HOWTO author).
Noted that some substitution operators come from ksh93.
Noted that a line of code in a script ending in a pipe character does
not require an escape to continue to the next line.
Code snippet on how to redirect "read" through an entire file, line by
line.
Added note that "declare" is Bash-specific.
Added code snippet explaining use of $IFS with "read"
Added alternate example of redirected "while" loop to "I/O Redirection"
section.
34) Added comments to "Subshells" section.
35) In "strip-comments.sh" example script, changed "=" to "-eq" (bugfix).
36) Changed all instances of "white space" to "whitespace" for consistency
(picky, picky).
37) Added pitfalls of variables in a subshell with illustrative example to
"Gotchas" section.
38) Added using Bash-specific functionality in a Bourne shell script on a
generic UNIX machine to "Gotchas" section.
39) Added another example to "List Constructs" section.
40) Added using positional paramters > $9, using {bracket} notation (thanks,
Philippe Martin).
41) Added -N and -t file tests to "Tests" section.
42) In "Arrays" section:
Added "q-function.sh" (Hofstadter's Q-function) as an illustrative
example.
Added "twodim.sh" simulation of a two-dimensional array.
43) Added two new entries to "Bibliography" section.
44) Added more info in "Quoting" section.
45) Bugfix: removed an extraneous header from "source/dot" command in "Special
Characters" section.
46) Added a caution about confusing REs with "globbing" to "Regular
Expressions" section.
47) In "Loops" Section:
Added filename "globbing" in for-loop [list].
Added "break N", breaking out of multiple loop levels.
Added "continue N", continuing at a higher loop level.
Added footnote to "Loop Control Commands" subsection noting that
"break" and "continue" are shell builtins.
48) Removed commented-out SGML code for article header. That makes it official
that this document is a book.
49) Added new appendix on "Converting DOS Batch Files to Shell Scripts".
50) Added "findstring.sh", illustrative example for generating [list] in a
"for" loop with command substitution and for "strings" command in
"External Filters, Programs, and Commands" section.
51) More info on "exit status".
52) Added appendix for "Exit Codes With Special Meanings".
53) Added "!" to "Special Characters" section.
54) Added "==" to "Tests" section.
55) Added a couple of examples and more explanation to "Regular
Expressions" section.
56) Extra notes on $BASH_VERSION.
57) In "Functions" section:
Added directing the stdin of a function, with illustrative example.
Added footnote to "return" command, noting that it is a Bash builtin.
58) Added "[[ ]]" construct to "Tests" section.
59) In "bubble.sh", fixed spelling of "Zaire" and changed "Kashmir" to "Kenya"
(it was pointed out that Kashmir is not a country).
60) Added "file-info.sh", illustrative example of a variable containing the
[list] in a "for" loop.
61) Added a section on "Scripting With Style", stylistic guidelines.
* Script and function headers added.
* Descriptive names for variables added.
62) Added "copy-cd.sh", a script for copying data CDs, to "Contributed
Scripts" section.
63) In "Loops" section, separated "Loop Control Commands" ("break" and "continue")
into a separate subsection.
64) Added note to "Tests" section that after "if", "test" or test brackets not
strictly necessary. Similarly, test brackets do not necessarily require an
"if" when used with "list constructions".
65) Once more, checked all the examples for stylistic correctness.
66) In "Variables Revisited" section:
Added "random-test.sh", testing the randomness of RANDOM.
Added "seeding-random.sh", reseeding the RANDOM generator.
67) Reshuffled some commands into different subsections in "External
Filters, Programs, and Commands" section.
68) Added "isalpha.sh" example to "case" constructs in "Loops" section.
69) Added inline example in "Regular Expressions" section.
70) Moved "ex50.sh" from "pr" to "fmt" in "External Filters, Programs, and
Commands" section.
71) Added "du.sh" example to "tr" in "External Filters, Programs, and
Commands" section.
72) Clarification on ${var#pattern}, ${var%pattern} variable substitution
in "Variables" section, and added "patt-matching.sh" example to
illustrate.
73) Clarifications on "ex14.sh" example.
74) In "Internal Commands and Builtins", fixed explanation on
"getopts" and associated "ex33.sh" to make usage consistent with
accepted usage. (Thanks, Ueli Strasser)
75) Fixed typos:
("suppress" --> "suppresses") in "Here Documents section.
("inderect" --> "indirect") in "Variables Revisited" section.
"Option" left out in "type" discussion.
76) More on "%" (modulo) operator in "Operations" section.
77) Added "> &FD" and "n<>filename" to "I/O Redirection" section.
78) Fixed bug in "ex2.sh" example (removed "or-list"),
and added cautionary not on "or lists".
79) More explanation on meaning of "keyword".
Noted that "!" is a keyword.
80) Moved "printf" and "eval" from "External Commands" to "Internal
Commands" section.
81) Fixed up some cross-reference links.
82) In "Sha-bang" section:
Added footnote with self-deleting script example.
Added footnote about invoking script with "sh scriptname" turning off
Added footnote about invoking a script with "./scriptname".
Bash-specific extensions.
Minor cleanups.
83) Cleaned up "filename" referenced.
Made references to "stdin" and "stdout" consistent (<filename>).
84) Added footnote about "dotfiles".
85) Noted that "logname" is not exact equivalent to "whoami", with example.
Correction: "trap 2" changes to "trap '' 2" in "Debugging" section.
Thank you, Nick Drage.
86) Fixed typos pointed out by Hyun Jin Chan.
Typo in "ex13.sh".
Typo in "ex41.sh".
In "Here Documents" section, changed
"feeding input into non-interactive programs" to
"feeding input into interactive programs".
87) Added footnote about "magic numbers" used in the context hard-wired
constants in "Scripting With Style" section.
88) Added "End Notes" chapter, which includes "Author's Note" and "Tool Used
to Produce This Book".
89) Added footnote about shell script naming conventions to "Why Shell
Programming?" section.
90) Changed all <errorcode> tags to the more appropriate <returnvalue>.
91) Added info about Korean translation of the document to "Copyright"
section.
92) Added "${#variable}" construct to "Parameter Substitution" subsection in
"Introduction to Variables and Parameters" section, mentioning exceptional
cases of "${#*}" and"${#@}".
93) Reorganized "I/O Redirection" section (subdivided into subsections).
94) Reorganized "Functions" section (subdivided into subsections).
95) Added example snippets to "Process Substitution" section.
96) Added Nick Drage's comments to "online.sh" in "Debugging" section.
97) Tidied up "Operations and Related Topics" section.
98) Fixed typos in "ex79.sh" ("suite" -> "suit").
99) Fixed other minor typos in the document.
100) Stephane Chazelas sent in long lists of corrections and suggestions.
Bug fixes, improvements, and comments on "ex2.sh" example.
Bug fixes and improvements to "ex3.sh" example.
Improvement on "ex4.sh", "ex5.sh", and "ex14.sh" examples.
Suggestion for "col-totaler.sh" example.
Code snippet on use of "case" for parsing command-line args.
In "brace expansion" discussion, pointed out that spaces permitted when
quoted or escaped.
Improved "ex8.sh" to read more than one line (more useful as an
example).
Resolve ambiguity about "-", which is not a Bash operator.
Suggested workarounds for filenames starting with "-" used with "-"
redirection operator.
Added safer alternatives to "ex58.sh".
In "Why Shell Programming?" section, modified footnote to state that
user-written scripts with ".sh" extension should be Bourne shell
compliant.
In "Command Substitution" section:
Added notes.
Added explanation in code snippet on command output.
Note that newline deletion may result from word splitting.
Added example snippets of trailing newline deletion.
In "Special Characters" section:
Fixed typo at beginning of "#" (comment) listing.
Added note about "#" not denoting a comment in certain constructs.
"${parameter?err_msg}, ${parameter:?err_msg}"
Added note that non-interactive script exits with code 127.
Added note about escaping "#" in echo statements.
Added caution about variable value starting with "-n".
More on "~" expansion.
Changed "noclobber" environmental variable (obsolete) to option.
Added "array initialization" to "()" listing.
Added notes to "brace expansion".
Added notes and made corrections to "ex6.sh" example.
Added note and example demonstrating that a code block in braces
may run as a subshell.
Clarification on "pipes".
Note on Alan Cox's directory copy method.
Noted that ":" is a shell builtin.
Noted that ": >>" applies only to regular files.
Fixed error about "code block" { ... }.
Added note about variables defined within (...) not being visible to
rest of script.
Fixed error on "{}\" construct, and added note.
Change to "uppercase.sh" in-line example.
Added "{#array}" as string length of first element of array.
Added cautionary note about reserved exit status codes to "Exit Status" section.
In "Variables" section:
Added comments and clarifications to "ex7.sh".
Added comments and clarifications to "ex9.sh".
Added info per his comments on the $'...' string expansion construct.
In "Quoting" section:
Added more examples of escaping a newline in variable assignment.
Clarified and corrected info about quoting variables "echoed", with
Added illustrative examples.
Replaced flawed example snippet ("bash$ echo [Ff]irst")
Fixed bug, changed ' to ` in referencing within double quotes.
Clarified and corrected "toggling on" special meanings of characters
by escaping.
In "Tests" section:
Added detailed explanation about "if/then" construct, "[", and "test".
Added clarification about "[", "[[" , and "test".
Added arithmetic tests using "(( ))".
Added notes to "ex10.sh" example.
Clarification on "ex12.sh", and moved it to "External Filters..." section.
Pointed out that one should always quote a string being tested.
Clarified what happens when erroneously putting a space in an
assignment statement.
Added example on using arithmetic operations (arithops.sh).
Clarification and corrections on "-t" test option.
Clarification on "-r" test option.
Clarification on "-w" test option.
Clarification on "-g" test option.
Clarification on "-u" test option.
Clarification on "-k" test option.
Clarification on "-n" test option.
Clarification on "str-test.sh" example.
Clarification and example on "==".
Clarification on pattern matching with "!=".
Clarification on "&&" and "||" comparison operators.
Fixup on "arith-tests.sh" example.
Clarification and corrections on "ex14.sh" example.
In "Operations" section:
Fixed "=" in-line example.
Fixed "+=" and "*=" example snippets.
Fixed typo: 'if "Xstring1" = "Xstring2" ] is safer,'.
Retitled subsections to avoid reader confusion.
Added example snippet on using "&&" and "||" in an arithmetic
context.
Added note to "arith-ops.sh".
Added note to "and-or.sh".
Fixed typo (lost space) in in-line "&&" example.
Clarified "numbers.sh" example.
Clarification on "&&" and "||".
In "Variables Revisited" section:
More clarifications and example snippets + "ifs.sh" example for "$IFS".
Clarified use of "$PATH" variable.
Cleared up confusion on "$PPID".
Cleared up confusion on "$@".
Added "incompat.sh" and "ifs-empty.sh" examples on inconsistent
"$*" and "$@" behavior.
Plugged a possible hole in "wipedir.sh" example script and added
comments.
Added "timeout.sh", another example of timed input.
Explanation (footnote) on environmental variables.
Explanation (footnote) on parameter $0.
Corrected "declare -f" listing.
Clarification on "ind-ref.sh" example.
Clarification on $SHELL variable.
Clarification on $HOSTNAME variable.
Added "col-totaler2.sh" as an example of indirect references.
Fixed typo "that that".
Fixup on "ex17.sh".
Fixup on "ex20.sh".
Added comment to "ex21.sh".
In "Loops" section:
Fixed error: semicolon *after* [list].
Additional clarification in "ex22a.sh" example.
Quoted arguments in [list] in for-loop illustration.
Removed reference to REs in filename globbing.
Fixup and note added to "list-glob.sh" example.
Added note to "bin-grep.sh" example.
Added note to "ex24.sh" example.
Correction on "ex26a.sh" example.
In "case" constructs:
Noted that variable quoting not mandatory.
Corrected and clarified comment in command line parameter testing.
Changed "regular expression" filtering to "globbing" filtering.
Improved "isalpha.sh" example.
In footnote, cleared up some confusion about builtins.
Moved 'basename', 'dirname', and 'factor' from "Internal Commands"
to "External Filters, Programs, and Commands" section.
Minor clarification on "read-redir.sh" example.
Alternatives added to "realname.sh" example.
In "Internal Commands and Builtins" section:
Corrections on "ps", "suspend", "command", and "builtin".
Moved "echo", "cd", and "let" here from "External Commands"
section.
Note on "echo" deleting linefeeds in command output.
Added in-line examples for "echo".
Correction on "find" (-exec).
Added "col-totaler3.sh" as an example of using "export" to
pass a variable to an embedded awk script.
Removed "stop" (how the heck did a "csh" command sneak in?).
Removed "." from examples of builtins.
Minor fixup on "ex33.sh" example.
Added cautionary note on "eval".
Added examples ("rot13_2.sh") to "eval".
Added long note to "jobs" command clarifying difference between jobs
and processes.
Added in-line example on "printf".
Clarified "keyword" definition.
Fixed typos in "read" and "find" command subsections.
In "External Filters, Programs, and Commands" section:
Clarifications on "chmod" and "chattr".
Added alternative method in "ex57.sh" example.
Clarification on "ex42.sh" example.
Clarification on "ex44.sh" example.
Clarification on "ex45.sh" example.
Option "-c" to "uniq" discussed.
Correction on "cut".
Clarification on "colrm".
Clarification on "join".
Clarification on "head", and added example "rnd.sh".
Concise form of "lookup.sh".
Clarification on "gs".
Added notes on "wc" (and fixup of example).
At "grep":
Additional minor fixups.
Note in "grp.sh" script.
Added usage examples for "-c" and "-z" options.
Added note on "time" about it becoming a reserved word.
Clarification and corrections on "tr".
Clarification in "ex49.sh" and "rot13.sh".
Added alternative code to "lowercase.sh".
Added note to "fmt" about Kamil Toman's "par" utility.
Added note to "line-number.sh" script about '-ba' option to 'nl'.
Clarification and fixup on "pr".
Added note to "zcat".
Added alternative code to "strip-comments.sh".
Fixed "lp".
Added two usage examples for "yes".
Added altenative methods to "find" in-line example.
Fixed format in "cat/tac" in-line example.
Added long note to "xargs".
Added note to "touch", and link from ":" in "Special Characters"
section.
Fixup on "zcat" in "gzip" subsection, and fixed typo there.
At "dd":
Added usage examples".
Fixed comments "dd-keypress.sh".
Fixed typo on "grep".
Explanatory note on "-maxdepth" option for "grep".
In "System Commands" section:
Moved "shopt" to "Internal Commands and Builtins".
More info on "who".
Correction and clarification on "hostname".
More info on "env".
Added "lsof".
Clarification on "pidof".
Moved "exec" to "Internal Commands and Builtins" and made some
corrections in the commentary.
Using "stty" to detect keypress, with illustrative example.
Fixup on "chgrp".
Fixup on "nice".
Fixup on "sync".
Added "createfs" example to illustrate "losetup".
At "stty", added long sidebar explaining canonical mode in terminals.
Fixup and additional illustrations on example.
Additional commentary on "ifconfig" code snippets.
Clarifications in "Arithmetic Expansion" section.
In "I/O Redirection" section:
Added note to "redir1.sh" example.
Added note to "redir2.sh" example.
Clarifications and notes added on "redir2a.sh", "redir3.sh",
"redir4.sh", and "redir5.sh" examples.
Added ": >" file truncation note.
Added examples (programlisting) of word splitting.
Added example of newline deletion.
Fixups (removed extraneous spaces in redirection operators in example
snippets).
Added alternative forms of operators that close file descriptors.
Added note and code snippet to "Closing File Descriptors" subsection.
Added "logevents.sh" example of using redirection operations in event
logging.
Added example snippet for "[j]<>filename".
In "Gotchas" section:
Fixed errors in using bad variable names.
Stylistic notes added.
Added note about attempting to use "-" as redirection operator.
Added notes and in-line example snippets about mixing up "=" and "-eq".
Correction on making script "suid".
Corrections and explanatory notes in "Regular Expressions" section.
Notes about "+" and curly brackets in "gawk".
Note and example ("newline.sh") about using "." to match newlines.
Footnote about matching dotfiles with globbing.
In "Subshells" section:
Fixup on in-line example.
Added example of subshell redirection.
Setting up a "dedicated environment" for a command group.
Added comment to code snippet illustrating parallel processes.
Added note about I/O redirection to subshells.
In "Functions" section:
Fix up and elaborate "ex60.sh" example.
Example ("ref-params.sh") of passing reference parameters to functions.
Comments and example on recursion.
Note and example snippet on declaring functions before calling them.
Note and example snippet on nested function.
Note and example snippet on function declarations in unlikely places.
Note and example snippet on using dedicated variables for return values.
Note and example snipptets on an alternative method of redirecting
the stdin of a function.
In "List Constructs" section:
Note and example snippets on operator precedence in compound
statements.
In "Arrays" section:
Added notes to "ex67.sh".
Added alternative implementation to "ex68.sh".
Added notes and example snippet on ${xxx[@]} and ${xxx[*]} notation.
Added notes to "twodim.sh" example.
Added "{#array}" as string length of first element of array.
Added "empty-array.sh" example.
In "Files" section, clarification on "/etc/profile".
In "Exit and Exit Status" section, added clarifying notes in in-line
example.
In "Here Documents" section:
Added note to "ex71.sh".
Fixup on "ex71c.sh".
Added note and example on "anonymous here documents".
Removed caution about pagers not working in a here document.
Added note about temporary files used by here documents.
In "Zeroes and Nulls" section, added note about ": >" alternate to
"cat /dev/null >".
In "Process Substitution" section:
Fixed error in note about not leaving space between ">(command)".
Changed "(command)>" to correct ">(command)".
Added example snippets.
In "Debugging" section:
Added commentary after "test24, another buggy script".
Correction on "exit" sending signal 0.
Added note and example ("vartrace.sh") in trapping discussion.
Notes added to "online.sh".
In "Miscellany" section:
Added using "[[ ]]" and "(( ))" in comparisons.
Corrections in discussion of interactive shells, plus
illustrative example.
In "Contributed Scripts" section:
Added "primes.sh" to demonstrate that arrays are not need to
generate prime numbers.
Added comments to "manview.sh"
Added comment to "tree.sh"
Added "obj-oriented.sh" example of object-oriented programming in a script.
Fixed error in comment in "pw.sh"
Notes on "string.sh".
In "Sed and Awk Micro-Primer" section, corrections, clarifications,
additions, and more examples.
In "Sample .bashrc File" appendix, correction pointing out that only
interactive shells read ".bashrc".
In "Sha-Bang" section:
Added note about the "#!" line being interpreted as a comment
by the command interpreter.
Added note about script needing read, as well as execute permission.
Added note about starting a "README" file with "#!/bin/more".
In "/dev and /proc" section:
Added note that /dev/sndstat has been eliminated as of the 2.3
kernel.
Clarification on virtual devices.
Simplified code snippets illustrating "extracting data" from /proc files.
Noted that /dev is not a file system.
Added commentary to "pid-identifier.sh" example.
Fixed error in footnote: entries in /dev do take up some space.
In "Options" section:
Clarified "-c" option.
Added note to "-u" option.
Fixed typo (--arg1arg2) on "--" (changed to "-- arg1 arg2")
In "Converting DOS Batch Files" section:
Removed unnecessary variable from "viewdata.sh" example.
Fixups on tables of DOS batch file / shell script equivalents.
In "Scripting With Style" section:
Fixup on example script.
Noted that "exit status" of a script is available to the parent process
of that script, not necessarily the shell.
Rewritten version of "example 3-2".
Added "A Detailed Introduction to I/O Redirection" appendix.
Added "Localization" appendix.
Made corrections.
======================================================================================
Version 0.3, released 02/12/01
Comments: Another major improvement. The HOWTO is nearly book length,
still evolving toward becoming a GUIDE.
Changes from version 0.2:
1) Fixed:
Renamed Example A-2 in Appendix A (Contributed Scripts) to
"encryptedpw". It had previously been named "manview", duplicating
the title of Example A-1.
2) In Chapter 1, the reader is now advised to use the example scripts
(something-or-other.sh), as an alternative to laboriously
cutting-and-pasting from rendered HTML.
3) In "Special Characters" section, added brace expansion {xxx,yyy,zzz...}.
4) Deleted the erroneous statement that the "set -r" option cannot be
invoked from within a script.
5) Added section for "restricted shells" with additional info.
6) Added a couple of script options.
7) Fixed minor bug in code snippet in "Interactive Scripts" section.
8) More info on interactive scripts.
9) Fixed an error confusing '$#' with '$*' in "Loops" section and in ex23.sh.
10) Added Antek Sawicki's random password script in contrib scripts.
In "External Filters, Programs, and Commands" section:
------------------------------------------------------
11) More accurately described the "{} \;" arguments to "find" command. Thanks
to Jim Van Zandt for pointing this out.
12) Added note to "xargs" that "echo" is default command. Again thanks
to Jim Van Zandt.
13) Fixed error claiming "diff" needs sorted files. Jim Van Zandt again.
14) Cleared up ambiguity about "colrm".
15) More info on "umask" and corrections.
16) Added "mkfifo".
------------------------------------------------------
17) Added cross-reference on "&&".
18) Added cross-reference to embedded sed script.
19) Added example of embedded awk script (col-totaler.sh).
20) Fixed clumsy wording in sed and awk description.
21) Added "su" to "System and Administrative Commands" section.
22) Added Jim Van Zandt's "daily backup" example script
to "Contrib-Scripts" section.
23) Enhanced example 66 (ex66.sh) on arrays with more methods of initializing
array variables.
24) Corrected "Siever" entry in bibliography.
25) Added Jordi Sanfeliu's "tree" script to "Contrib-Scripts" section.
26) Added Robbins' "Bash Reference Card" to bibliography.
27) Added reference to Duarte's sed tutorial in bibliography.
28) Added "rn.sh", file rename utility to "Contrib-Scripts" section.
29) Added "initializing multiple variables on same line" to ex9.sh.
30) Fixed title on "ex52.sh".
31) Added a case when not to use shell scripts, in intro.
32) Added shell script as embedded command in another script, Tcl or wish
script, etc. to "Miscellany / Assorted Tips" section.
33) Added download link for latest version of document to intro.
34) Added "id" to "System and Administrative Commands" section.
35) Added "stty" to "System and Administrative Commands" section.
36) Added "strip-comments.sh" example to illustrate "file" command,
and "rot13.sh" example to "tr" command, in "External Filters" section.
37) Added "modular approach" sidebar to Chapter 2, section 1.
38) Added example cross-references to use of REs in scripts by sed,
awk, and Perl.
39) More info and clarification on command substitution and arithmetic
expansion in "Backticks" section.
40) Corrected "Bibliography" section entry for Ben Okopnik's introductory
Bash scripting articles in "Linux Gazette".
41) Added "Bibliography" section entries for "Bash-Prompt HOWTO" and
"Bash-Programming-Intro HOWTO".
42) Added $OLDPWD, $BASH_VERSION, $DIRSTACK, $HOSTNAME, $PPID, $MACHTYPE,
$HOSTTYPE, $OSTYPE, $UID, $EUID, $SHELLOPTS, $IGNOREEOF, and $GROUPS
to internal Bash variables in "Variables Revisited" section.
43) Added info on the "-" operator (may also be interpreted as "old
working directory", depending on context).
44) Added collecting favorite definitions and functions into "library file" to
"Miscellany / Assorted Tips" section.
45) Added cross reference from "dot" command to "source", later on in
tutorial.
46) In "Special Characters" section, noted that a command may not follow
a comment on the same line.
47) Added section on "Aliases", including two example scripts.
48) Added discussion of "for" loops with multiple parameters in each [list]
element to "Loops Section".
49) Added discussion of "while" loops with multiple conditions to "Loops
Section".
50) Added cross-reference to mention of "getopts" in "while loops" discussion.
51) Added cross-reference on "exec" in "System and Administrative Commands"
section back to use of "exec" in "find" command sequence in "External
Filters, Programs, and Commands" section. Added other cross-references in
this section.
52) Added footnote about fd 5 being reserved to "I/O Redirection" section.
53) Additional discussion in "I/O Redirection" section.
54) Added using "exec" to redirect stdin to "I/O Redirection" section.
55) Added "redir1.sh", example of I/O redirection using "exec".
56) Added "redir2.sh", example of I/O redirected "while" loop.
57) Added "redir3.sh", example of I/O redirected "until" loop.
58) Added "redir4.sh", example of I/O redirected "for" loop.
59) Added "redir5.sh", example of I/O redirected "if/then" test.
60) Added "wipedir.sh" example to $PWD listing in "Variables Revisited"
section.
61) More cross-references in "I/O Redirection" section.
62) Added "grp.sh", 'grep' emulation script, after 'grep' listing
in "External Filters, Programs and Commands" section.
63) Added "nice", "arch", "users" , "logname", "dmesg", "groups",
"hostname", and "pidof" to "System and Administrative Commands"
section.
64) Added "bzip2", "sq", "rev", "strings", "pathchk" and references to
"egrep", "fgrep" , "groff, gs, TeX", "column", "look", "ptx",
"chattr", "cal", "nslookup", "traceroute", "dig", "rx/sx", "rz/sz",
"uucp", and "sum, cksum, md5sum" to "External Filters, Programs and
Commands" section. Also added illustrative examples for "column"
and "look".
65) Added bibliography entries for GNU "gawk" reference manual and "groff"
tutorial. Also for I/O reference on UAlberta site.
66) Added cross-references to script examples to "zcat" and "mv"
commands" in "External Filters, Programs and Commands" section.
67) Clarification on [ -n $string ] string test operator. Added illustrative
example (str-test.sh).
68) Added "lp" and related commands to "External Filters, Programs and
Commands" section.
69) Added double-quoting variables to "Gotchas" section.
70) Added more xrefs to examples in "Variables Revisited" section.
71) Added "PS3" and "PS4" to "Variables Revisited" section.
72) Added enabling script options from #! header to "Options" section.
73) Added double backslash (\\) to "Quoting" section.
74) Added "Sed and Awk Micro-primer" appendix.
75) Fuller explanation of differences between "$*" and "$@" in "Variables
Revisited" section. Also added example to illustrate this,
"arglist.sh".
76) More cross-references to examples in "System and Administrative Commands"
section.
77) Added more detail to description of $PATH, in "Variables Revisited"
section.
78) Added more detail to "Files" section.
79) Added "command", "enable", , "builtin", "host", and "vrfy" to
"Internal Commands and Builtins" section.
80) Moved "umask" from "External Filters, Programs, and Commands" to "System
and Administrative Commands" section.
81) Rearranged the entries in "External Filters, Programs and Commands" in
somewhat more logical order and subdivided the section into logical
subsections.
82) Moved discussion of embedded Perl scripts from "System and Administrative
Commands" section to "Shell Wrappers" subsection.
83) Added example .bashrc file, thanks to Emmanuel Rouat.
84) Many minor changes not listed above.
====================================================================
Version 0.2, released 10/30/00.
Comments: This is a major improvement over 0.1.
Changes from version 0.1:
Bugfixes
1) fixed if [ cond1 && cond2 ] ==> if [ cond1 ] && [ cond2 ]
if [ cond1 || cond2 ] ==> if [ cond1 ] || [ cond2 ]
Added -a and -o options
if [ cond1 -a cond2 ]
if [ cond1 -o cond2 ]
Added 'and-or.sh' as new example to illustrate && and ||.
2) Corrected ex6.sh, added $'s in front of {USER?} and {MAIL?},
and added additional explanatory material.
3) Noted that "-" is not a bash option.
Other changes
4) ex55.sh: added note that 'killall' is Red Hat specific
5) Added to 'Gotchas':
interchanging -eq and =
starting variables with a digit
6) Substituted for Samuel Johnson quote at beginning:
"...there are dark corners in the Bourne shell, and people use all of them."
--Chet Ramey
7) Added reference to /usr/doc/initscripts-X.XX/sysconfig.txt just after
ex. 3-52.
8) Added reference to 'nl' in "External Filters" section and illustrative
example.
9) Added material to 'cat' listing.
10) Added:
cd source-directory
tar cf - . | (cd ../target-directory; tar xzf -)
to Alan Cox example as an alternative.
11) Added material & example to {}
12) Added "Renaming file extensions" example
to pattern matching section.
13) Added "Bash F.A.Q." and "sed F.A.Q." to references.
14) Added missing line in "Tests" section.
15) Revised the 'abstract'.
16) Added <revhistory> element.
17) Reorganized:
Moved two examples placed erroneously in 'backticks' section
to where they belong.
18) Fleshed out section on 'subshells'.
Added 2 examples.
19) Rewrote text to first 'variables' section.
20) Added "rpm-check.sh" example to "code blocks" discussion.
21) Added "online.sh" example to "trap" discussion.
22) Expanded "I/O Redirection" section
Definition of 'file descriptor' added.
More on file descriptors 3 - 9.
23) Expanded "Regular Expression" section.
24) Added explanation of signals to "debugging" section.
25) Added SECONDS and REPLY to internal variables listing (plus illustrative
examples).
26) Added 'ulimit' to administrative commands listing.
27) Added more information on 'trap' in 'Debugging' section.
28) Fixed erroneous '==' reference in 'Variables Revisited section.
29) Added 'jobs', 'ps', and 'nohup' to 'Administrative Commands' section.
30) Added additional entries to file tests in 'Tests' section.
31) Added additional entries and much more detail in 'Options' section.
32) More detail on 'grep'.
33) More detail on 'export'.
34) Added entries to file and string tests.
35) Added 'uptime' to 'System and Administrative Commands' section.
36) Added '~' to 'Special Characters' section.
37) Added material to 'Backquotes' section.
38) Added 'which' to 'External Filters and Commands' section.
39) More detail on parameters to functions.
40) More detail on arrays.
41) More detail on 'at'.
42) More detail on $RANDOM. Expanded example.
43) Added example script to demonstrate timed input.
44) Added 'Representation of Numerical Constants' subsection to 'Operations'
section.
45) Added "eval var1=\$$var2" indirect reference notation to 'Variables
Revisited' section.
46) Reorganized:
Moved 'Parameter Substition' discussion from 'Special Characters' section
to 'Variables' section.
Added extra illustrative code snippets.
47) Added bubble sort example to 'Arrays' section.
48) Added %= operator to 'Operations' section.
49) Added reference to 'whoami' to 'System and Administrative Commands'
section.
50) More detail and an additional example for 'Quoting' section.
51) Added info on using pattern match operator, ${var/patt/}, for deletion.
52) More detail on 'touch' and 'read' in 'External Filters'.
53) More detail on 'null' operator (:).
54) Some of the preexisting examples revised, with more material.
55) 'Miscellany' section added.
subsection 'Interactive Scripts'
subsection 'Optimizations'
subsection 'Assorted Tips'
56) Contrib script section added
4 scripts so far.
57) Expanded 'Credits' section.
58) Many other corrections, minor changes, and additions.
====================================================================
Version 0.1 released 14 June, 2000.
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