Section C: Differences from other Unix shells
C：跟其他UNIX shells脚本的区别
C1) How does bash differ from sh, the Bourne shell?
C1） bash和 sh、Bourne shell的区别
This is a non-comprehensive list of features that differentiate bash
from the SVR4.2 shell.  The bash manual page explains these more
completely.
这时一个不全面的bash和SVR4.2 shell特性区别的列表，bash手册解释的更详细
Things bash has that sh does not:
bash特有的功能：
        long invocation options
        长选项的调用
        [+-]O invocation option
        -l invocation option
        `!' reserved word to invert pipeline return value
         ！叹号保留字对管道返回的值取反
        `time' reserved word to time pipelines and shell builtins
         time保留字测试管道或内建命令耗时情况
        the `function' reserved word
        the `select' compound command and reserved word
        select复合命令和保留字
        arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
        算术命令：for ((expr1 ; expr2; expr3 )); do list; done
        new $'...' and $"..." quoting
        新的引用方法$'...'  $"..."
        the $(...) form of command substitution
        $(...) 命令替代用法
        the $(filename) form of command substitution, equivalent to
                $(cat filename)
        $(filename)形式的命令的替换，相当于$(cat filename)
        the ${#param} parameter value length operator
        ${#param} 测试参数param的值的长度
        the ${!param} indirect parameter expansion operator
        ${!param} 间接参数扩展操作
        the ${!param*} prefix expansion operator
        ${!param*} 前缀扩展操作
        the ${param:offset[]} parameter substring operator
       ${param:ffset[]}参数通过偏移量截取子串操作
        the ${param/pat[/string]} parameter pattern substitution operator
        ${param/pat[/string]} 参数模式替换的操作
        expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
         扩展子串删除命令：(${p%[%]w}, ${p#[#]w})
        expansion of positional parameters beyond $9 with ${num}
        扩展了为止参数超过9的限制
        variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY,
                   TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS,
                   LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME,
                   ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE,
                   HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS,
                   PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC,
                   SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars,
                   auto_resume
        上边一堆的环境变量
        DEBUG trap
        ERR trap
        调试和错误陷阱
        variable arrays with new compound assignment syntax
         数组和复合赋值运算符的语法规则
        redirections: >, >, >|, , [n]word-, [n]>word-
         重定向规则： >, >, >|, , [n]word-, [n]>word-
        prompt string special char translation and variable expansion
        提示字符串特殊字符的转化和变量展开
        auto-export of variables in initial environment
        自动继承初始化的环境变量
        command search finds functions before builtins
        命令搜查函数限于内建命令
        bash return builtin will exit a file sourced with `.'
        bash返回内建命令 将退出一个.文件源
        builtins: cd -/-L/-P, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
                  export -n/-f/-p/name=value, pwd -L/-P,
                  read -e/-p/-a/-t/-n/-d/-s/-u,
                  readonly -a/-f/name=value, trap -l, set +o,
                  set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
                  unset -f/-v, ulimit -m/-p/-u,
                  type -a/-p/-t/-f/-P, suspend -f, kill -n,
                  test -o optname/s1 == s2/s1 s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S
        上边一堆内建命令
        bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
        bash reads这样写交互脚本，环境变量非交互的。
        bash restricted shell mode is more extensive
        bash更广泛的受限模式
        bash allows functions and variables with the same name
        允许函数名变量名一样
        brace expansion
        括号扩展
        tilde expansion
        ～波浪号扩展
        arithmetic expansion with $((...)) and `let' builtin
        算术扩展：$((...)) 和let命令
        the `...' extended conditional command
        `...` 命令扩展
        process substitution
        进程替换
        aliases and alias/unalias builtins
        别名的内建命令
        local variables in functions and `local' builtin
        函数内本地变量
        readline and command-line editing with programmable completion
        读取行和命令行可以编程完成
        command history and history/fc builtins
         查看历史命令
        csh-like history expansion
        other new bash builtins: bind, command, compgen, complete, builtin,
                                 declare/typeset, dirs, enable, fc, help,
                                 history, logout, popd, pushd, disown, shopt,
                                 printf
         上边一堆新的bash内建命令。
        exported functions
        filename generation when using output redirection (command >a*)
        重定向输出文件名的生成
        POSIX.2-style globbing character classes
        POSIX.2-style globbing equivalence classes
        POSIX.2-style globbing collating symbols
        POSIX.2风格的通配符类、等价类、通配符号
        egrep-like extended pattern matching operators
        case-insensitive pattern matching and globbing
        不区分大小写的模式匹配和通配符
        variable assignments preceding commands affect only that command,
                even for builtins and functions
        变量赋值前的命令只影响那个命令，包括内建命令和函数
        posix mode
        redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
                /dev/tcp/host/port, /dev/udp/host/port
        debugger support, including `caller' builtin and new variables
        调试支持，包括caller内建命令和新变量
        RETURN trap

 
Things sh has that bash does not:
下边是sh有但是bash木有的
        uses variable SHACCT to do shell accounting
        includes `stop' builtin (bash can use alias stop='kill -s STOP')
        `newgrp' builtin
        turns on job control if called as `jsh'
        $TIMEOUT (like bash $TMOUT)
        `^' is a synonym for `|'
        new SVR4.2 sh builtins: mldmode, priv

Implementation differences:
执行情况的不同：
        redirection to/from compound commands causes sh to create a subshell
        bash does not allow unbalanced quotes; sh silently inserts them at EOF
        bash does not mess with signal 11
        sh sets (euid, egid) to (uid, gid) if -p not supplied and uid 100
        bash splits only the results of expansions on IFS, using POSIX.2
                field splitting rules; sh splits all words on IFS
        sh does not allow MAILCHECK to be unset (?)
        sh does not allow traps on SIGALRM or SIGCHLD
        bash allows multiple option arguments when invoked (e.g. -x -v);
                sh allows only a single option argument (`sh -x -v' attempts
                to open a file named `-v', and, on SunOS 4.1.4, dumps core.
                On Solaris 2.4 and earlier versions, sh goes into an infinite
                loop.)
        sh exits a script if any builtin fails; bash exits only if one of
                the POSIX.2 `special' builtins fails

下边都和上边比较雷同了。。。大致浏览吧。
C2) How does bash differ from the Korn shell, version ksh88?

Things bash has or uses that ksh88 does not:
        long invocation options
        [-+]O invocation option
        -l invocation option
        `!' reserved word
        arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
        arithmetic in largest machine-supported size (intmax_t)
        posix mode and posix conformance
        command hashing
        tilde expansion for assignment statements that look like $PATH
        process substitution with named pipes if /dev/fd is not available
        the ${!param} indirect parameter expansion operator
        the ${!param*} prefix expansion operator
        the ${param:offset[]} parameter substring operator
        the ${param/pat[/string]} parameter pattern substitution operator
        variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, SHLVL,
                   TIMEFORMAT, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE,
                   HISTFILESIZE, HISTIGNORE, HISTCONTROL, PROMPT_COMMAND,
                   IGNOREEOF, FIGNORE, INPUTRC, HOSTFILE, DIRSTACK,
                   PIPESTATUS, HOSTNAME, OPTERR, SHELLOPTS, GLOBIGNORE,
                   GROUPS, FUNCNAME, histchars, auto_resume
        prompt expansion with backslash escapes and command substitution
        redirection: > (stdout and stderr), , [n]word-, [n]>word-
        more extensive and extensible editing and programmable completion
        builtins: bind, builtin, command, declare, dirs, echo -e/-E, enable,
                  exec -l/-c/-a, fc -s, export -n/-f/-p, hash, help, history,
                  jobs -x/-r/-s, kill -s/-n/-l, local, logout, popd, pushd,
                  read -e/-p/-a/-t/-n/-d/-s, readonly -a/-n/-f/-p,
                  set -o braceexpand/-o histexpand/-o interactive-comments/
                  -o notify/-o physical/-o posix/-o hashall/-o onecmd/
                  -h/-B/-C/-b/-H/-P, set +o, suspend, trap -l, type,
                  typeset -a/-F/-p, ulimit -u, umask -S, alias -p, shopt,
                  disown, printf, complete, compgen
        `!' csh-style history expansion
        POSIX.2-style globbing character classes
        POSIX.2-style globbing equivalence classes
        POSIX.2-style globbing collating symbols
        egrep-like extended pattern matching operators
        case-insensitive pattern matching and globbing
        `**' arithmetic operator to do exponentiation
        redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr
        arrays of unlimited size
        TMOUT is default timeout for `read' and `select'
        debugger support, including the `caller' builtin
        RETURN trap
        Timestamps in history entries
        {x..y} brace expansion

Things ksh88 has or uses that bash does not:
        tracked aliases (alias -t)
        variables: ERRNO, FPATH, EDITOR, VISUAL
        co-processes (|, >p, p)
        weirdly-scoped functions
        typeset +f to list all function names without definitions
        text of command history kept in a file, not memory
        builtins: alias -x, cd old new, newgrp, print,
                  read -p/-s/var?prompt, set -A/-o gmacs/
                  -o bgnice/-o markdirs/-o trackall/-o viraw/-s,
                  typeset -H/-L/-R/-Z/-A/-ft/-fu/-fx/-l/-u/-t, whence
        using environment to pass attributes of exported variables
        arithmetic evaluation done on arguments to some builtins
        reads .profile from $PWD when invoked as login shell

Implementation differences:
        ksh runs last command of a pipeline in parent shell context
        bash has brace expansion by default (ksh88 compile-time option)
        bash has fixed startup file for all interactive shells; ksh reads $ENV
        bash has exported functions
        bash command search finds functions before builtins
        bash waits for all commands in pipeline to exit before returning status
        emacs-mode editing has some slightly different key bindings

 
C3) Which new features in ksh-93 are not in bash, and which are?

New things in ksh-93 not in bash-3.0:
        associative arrays
        floating point arithmetic and variables
        math library functions
        ${!name[sub]} name of subscript for associative array
        `.' is allowed in variable names to create a hierarchical namespace
        more extensive compound assignment syntax
        discipline functions
        `sleep' and `getconf' builtins (bash has loadable versions)
        typeset -n and `nameref' variables
        KEYBD trap
        variables: .sh.edchar, .sh.edmode, .sh.edcol, .sh.edtext, .sh.version,
                   .sh.name, .sh.subscript, .sh.value, .sh.match, HISTEDIT
        backreferences in pattern matching (\N)
        `' operator in pattern lists for matching
        print -f (bash uses printf)
        `fc' has been renamed to `hist'
        `.' can execute shell functions
        exit statuses between 0 and 255
        `+=' variable assignment operator
        FPATH and PATH mixing
        getopts -a
        -I invocation option
        printf %H, %P, %T, %Z modifiers, output base for %d
        lexical scoping for local variables in `ksh' functions
        no scoping for local variables in `POSIX' functions

New things in ksh-93 present in bash-3.0:
        [n]word- and [n]>word- redirections (combination dup and close)
        for (( expr1; expr2; expr3 )) ; do list; done - arithmetic for command
        ?:, ++, --, `expr1 , expr2' arithmetic operators
        expansions: ${!param}, ${param:offset[]}, ${param/pat[/str]},
                    ${!param*}
        compound array assignment
        the `!' reserved word
        loadable builtins -- but ksh uses `builtin' while bash uses `enable'
        `command', `builtin', `disown' builtins
        new $'...' and $"..." quoting
        FIGNORE (but bash uses GLOBIGNORE), HISTCMD
        set -o notify/-C
        changes to kill builtin
        read -A (bash uses read -a)
        read -t/-d
        trap -p
        exec -c/-a
        `.' restores the positional parameters when it completes
        POSIX.2 `test'
        umask -S
        unalias -a
        command and arithmetic substitution performed on PS1, PS4, and ENV
        command name completion
        ENV processed only for interactive shells
        set -o pipefail