shell的内置命令

0Jip t(P"D1p0    有时使用man查看某个命令（如cd）的帮助信息时会显示形如下面的信息：

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   这表示该命令为shell的内置命令，使用type命令查看的话返回下面的信息：51Testing软件测试网R6f&kp_'j

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!o n N2DF[8V5^v0关于shell的这些内置的命令，由于执行时不需要到磁盘上查找，因此速度比较快。使用不带参数的help（bash内置命令）命令，可以查看这些内置命令列表，使用help commandname 可以查看command的详细信息。大概有下面这些内置命令：

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 (( expression ))
+Ir&~t
Y"_.[0 [[ expression ]]
l#]9O:m$D0 . filename [arguments]51Testing软件测试网:b:]3RYB;Ua-Y-k-f
 :                                           
-sxhx&O4Cu0 alias [-p] [name[=value] ... ]    51Testing软件测试网Q4w] P+G9ur+b
 [ arg... ]                        
y5QU5S#[j0 bg [job_spec]                               
v0sO_fp(^0 bind [-lpvsPVS] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readline-function or readline-command]51Testing软件测试网YAEK]+@@2b#] cu N
 break [n]                                   
@m+j9TE`;b,R-L`J0 builtin [shell-builtin [arg ...]] 51Testing软件测试网2D7ym/C7I#_ofl
 caller [EXPR]                               51Testing软件测试网&LN_ JV
 case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac
`W ^ f ej0d |+Q f0 cd [-L|-P] [dir]                            
rC.?I"F(yzR6_YT0 command [-pVv] command [arg ...]  
,G]$Kv7]0 compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-P prefix] [-S suffix] [-X filterpat] [-F function] [-C command] [word]          
)PpYi0um-\7P0 complete [-abcdefgjksuv] [-pr] [-o option] [-A action] [-G globpat] [-W wordlist] [-P prefix] [-S suffix] [-X filterpat] [-F function] [-C command] [name ...]51Testing软件测试网\Pu \rOgh
 continue [n]                                51Testing软件测试网nJl:dGhvRD
 declare [-afFirtx] [-p] [name[=value] ...]
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mU!`^0 dirs [-clpv] [+N] [-N]                      51Testing软件测试网7QylSQQ
 disown [-h] [-ar] [jobspec ...]   
F(QX#j4F0 echo [-neE] [arg ...]                       51Testing软件测试网n5{_$v0H(x9hN
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  enable [-pnds] [-a] [-f filename] [name ...] 
U5Mu @$kb Y0 eval [arg ...]                              51Testing软件测试网%t2j$In#?0P r
 exec [-cl] [-a name] file [redirection ...]51Testing软件测试网cx2KX^$q
 exit [n]                                    51Testing软件测试网2@#Y"h p {g
 export [-nf] [name[=value] ...] or export -p                              51Testing软件测试网cv
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 false                                       
hr'f'pyt u0 fc [-e ename] [-nlr] [first] [last] or fc -s [pat=rep] [cmd]51Testing软件测试网$M-L*`)MJ.eM+r9M`Y1u
 fg [job_spec]            
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s/K0^0 for ((: for (( exp1; exp2; exp3 )); do COMMANDS; done  
[b"jL)gv\&R0 for NAME [in WORDS ... ;] do COMMANDS; done51Testing软件测试网I,p2_v*G5c&@
 function NAME { COMMANDS ; } or NAME () { COMMANDS ; }
6CN.z9NZA,gC0 getopts optstring name [arg]                
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Z3A0Mr%_*T0 hash [-lr] [-p pathname] [-dt] [name ...]51Testing软件测试网]RL D1n_2j
 help [-s] [pattern ...]                     51Testing软件测试网E$}-o(\x^+W/k S.~
 hhistory [-c] [-d offset] [n] or history -awrn [filename] or history -ps arg [arg...]51Testing软件测试网8~-@ }F&e
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 if COMMANDS; then COMMANDS; [ elif COMMANDS; then COMMANDS; ]... [ else COMMANDS; ] fi          
l9uE/p uWZ K,\;pv0 jobs [-lnprs] [jobspec ...] or jobs -x command [args]
)S$f]g xW,Y&W0 kill [-s sigspec | -n signum | -sigspec] [pid | job]... or kill -l [sigspec]          51Testing软件测试网3hK9dOCc1s%xP;WRtz
 let arg [arg ...]                 51Testing软件测试网vm&@3[!l*\)v-S!@
 local name[=value] ...                      
r|Y?2G!fg8Je6aR0 logout                            51Testing软件测试网'b|} ]!T
 popd [+N | -N] [-n]                         51Testing软件测试网4HWaUl@O"r r\
 printf format [arguments]         
T%ke[]#m6N0 pushd [dir | +N | -N] [-n]                  51Testing软件测试网%bQ`7e'zmM3q/\f^w
 pwd [-PL]                         
9F~fa D?0 read [-ers] [-u fd] [-t timeout] [-p prompt] [-a array] [-n nchars] [-d delim] [name ...]          51Testing软件测试网*uH SX|wdCj,vy
 readonly [-af] [name[=value] ...] or readonly -p 
'LvS9g-B3gZs0 return [n]                                  
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x8]cV0 select NAME [in WORDS ... ;] do COMMANDS; done51Testing软件测试网PA(IM`L
 set [--abefhkmnptuvxBCHP] [-o option] [arg ...]          
S8g)RYM&h0 shift [n]                         51Testing软件测试网dyS8^,lL
 shopt [-pqsu] [-o long-option] optname [optname...]          51Testing软件测试网}s2Ic Bq)M3i:~
 source filename [arguments]       
u!@s~1c0 suspend [-f]                                
'_s?-LvN0 test [expr]                       
@0J$o4]2KJ#b}s0 time [-p] PIPELINE                          
[ T ya(B)c)` h0 times                             51Testing软件测试网kbEyaRa
} F-m
 trap [-lp] [arg signal_spec ...]            
[3_.vs.@3G?H*c,H0 true                              
{H]^vW!zD.P/q0 type [-afptP] name [name ...]               51Testing软件测试网0s;s-z*B"{ ['I
 typeset [-afFirtx] [-p] name[=value] ...51Testing软件测试网K{0@H*{
 ulimit [-SHacdflmnpstuv] [limit]            51Testing软件测试网^8Z`a:eB6u
 umask [-p] [-S] [mode]            
` `3U&wf3V(U0 unalias [-a] name [name ...]                51Testing软件测试网Xf w7?5h,n+X
 unset [-f] [-v] [name ...]        51Testing软件测试网$cgSN5Ezj
 until COMMANDS; do COMMANDS; done           
(jXtc6D w"qR#IoZ0 variables - Some variable names and meanings51Testing软件测试网Q.d:C@Z5g8w+R"M
 wait [n] 

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