内置命令到底能不能用which查找其完整路径？

telnetp

[root@MGWSDT_FEWS bin]# type cd
cd is a shell builtin
[root@MGWSDT_FEWS bin]# which cd
/usr/bin/which: no cd in (.:/usr/expect/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/opt/real/RealPlayer:/root/bin)
鸟哥私房菜对此的解释是因为cd是内置命令，故which cd找不到。
但pwd也是内置命令，为什么用which命令可以找到呢？
[root@MGWSDT_FEWS ~]# type pwd
pwd is a shell builtin
[root@MGWSDT_FEWS ~]# which pwd
/bin/pwd

chenyx

$ which pwd
/bin/pwd

你的是什么系统?我这里pwd不是内置的

ooooldman

内部命令是shell 自带的，你怎么查

telnetp

这是我的系统：
[root@MonitoringServer ~]# lsb_release -a
LSB Version:    :core-4.0-ia32:core-4.0-noarch:graphics-4.0-ia32:graphics-4.0-noarch:printing-4.0-ia32:printing-4.0-noarch
Distributor ID: RedHatEnterpriseWorkstation
Description:    Red Hat Enterprise Linux Workstation release 6.3 (Santiago)
Release:        6.3
Codename:       Santiago

wjg501917603

为了实现执行的效率，shell内置命令是在源码中实现的，在linux文件中查找不到的，
如果能查找到那也就不能叫内置命令了。另外which命令是会去环境变量的PATH中找，不在PATH中就找不到的。

wjg501917603

pwd不是内置命令，它在/bin/pwd

telnetp

可是
[root@MGWSDT_FEWS bin]# type cd
cd is a shell builtin
[root@MGWSDT_FEWS ~]# type pwd
pwd is a shell builtin

这里都说是 ‘ is a shell builtin’啊？为什么pwd不是内置命令呢？

seanking1987

BASH_BUILTINS(1)                                              BASH_BUILTINS(1)

NAME
       bash,  :,  .,  [,  alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo, enable, eval, exec, exit, export, fc, fg,
       getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly, return, set, shift, shopt,  source,  suspend,  test,  times,
       trap, type, typeset, ulimit, umask, unalias, unset, wait - bash built-in commands, see bash(1)

which pwd为/bin/pwd

个人判断：pwd既是内建命令，也是外部命令

$type -a pwd
pwd is a shell builtin
pwd is /bin/pwd

seanking1987

BASH_BUILTINS(1)                                              BASH_BUILTINS(1)

NAME
       bash,  :,  .,  [,  alias, bg, bind, break, builtin, cd, command, compgen, complete, continue, declare, dirs, disown, echo, enable, eval, exec, exit, export, fc, fg,
       getopts, hash, help, history, jobs, kill, let, local, logout, popd, printf, pushd, pwd, read, readonly, return, set, shift, shopt,  source,  suspend,  test,  times,
       trap, type, typeset, ulimit, umask, unalias, unset, wait - bash built-in commands, see bash(1)

which pwd为/bin/pwd

个人判断：pwd既是内建命令，也有外部命令

$type -a pwd
pwd is a shell builtin
pwd is /bin/pwd

telnetp

多谢seanking1987，这个解释合理！