csh,tcsh,bash,sh 등 셸 의 차이

Section C: Differences from other Unix shells
C：   UNIX shells     
C1) How does bash differ from sh, the Bourne shell?
C1） bash  sh、Bourne shell   
This is a non-comprehensive list of features that differentiate bash
from the SVR4.2 shell.  The bash manual page explains these more
completely.
        bash SVR4.2 shell       ，bash        
Things bash has that sh does not:
bash     ：
        long invocation options
              
        [+-]O invocation option
        -l invocation option
        `!' reserved word to invert pipeline return value
         ！              
        `time' reserved word to time pipelines and shell builtins
         time                
        the `function' reserved word
        the `select' compound command and reserved word
        select        
        arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
            ：for ((expr1 ; expr2; expr3 )); do list; done
        new $'...' and $"..." quoting
              $'...'  $"..."
        the $(...) form of command substitution
        $(...)       
        the $(<filename) form of command substitution, equivalent to
                $(cat filename)
        $(<filename)        ，   $(cat filename)
        the ${#param} parameter value length operator
        ${#param}     param     
        the ${!param} indirect parameter expansion operator
        ${!param}         
        the ${!param*} prefix expansion operator
        ${!param*}       
        the ${param:offset[]} parameter substring operator
       ${param:ffset[]}             
        the ${param/pat[/string]} parameter pattern substitution operator
        ${param/pat[/string]}          
        expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
                 ：(${p%[%]w}, ${p#[#]w})
        expansion of positional parameters beyond $9 with ${num}
                 9   
        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
                 
        DEBUG trap
        ERR trap
               
        variable arrays with new compound assignment syntax
                        
        redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-
              ： <>, &>, >|, <<<, [n]<&word-, [n]>&word-
        prompt string special char translation and variable expansion
                         
        auto-export of variables in initial environment
                    
        command search finds functions before builtins
                    
        bash return builtin will exit a file sourced with `.'
        bash            .   
        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
                
        bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
        bash reads       ，        。
        bash restricted shell mode is more extensive
        bash        
        bash allows functions and variables with the same name
                  
        brace expansion
            
        tilde expansion
        ～     
        arithmetic expansion with $((...)) and `let' builtin
            ：$((...))  let  
        the `...' extended conditional command
        `...`     
        process substitution
            
        aliases and alias/unalias builtins
               
        local variables in functions and `local' builtin
               
        readline and command-line editing with programmable completion
                     
        command history and history/fc builtins
               
        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
               bash    。
        exported functions
        filename generation when using output redirection (command >a*)
                   
        POSIX.2-style globbing character classes
        POSIX.2-style globbing equivalence classes
        POSIX.2-style globbing collating symbols
        POSIX.2       、   、    
        egrep-like extended pattern matching operators
        case-insensitive pattern matching and globbing
                       
        variable assignments preceding commands affect only that command,
                even for builtins and functions
                       ，         
        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
            ，  caller        
        RETURN trap

 
Things sh has that bash does not:
   sh   bash   
        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:
       ：
        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

           。。。     。
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