type命令用来显示指定命令的类型。一个命令的类型可以是如下之一
它是Linux系统的一种自省机制，知道了是那种类型，我们就可以针对性的获取帮助。比如内建命令可以用help命令来获取帮助，外部命令用man或者info来获取帮助。
type命令的基本使用方式就是直接跟上命令名字。
type -a可以显示所有可能的类型，比如有些命令如pwd是shell内建命令，也可以是外部命令。
type -p只返回外部命令的信息，相当于which命令。
type -f只返回shell函数的信息。
type -t 只返回指定类型的信息。
[root@new55 ~]# type -a type
type is a shell
builtin
[root@new55 ~]# help type
type: type
[-afptP] name [name ...]
For each NAME, indicate how it
would be interpreted if used as a
command
name.
If the -t option is
used, `type‘ outputs a single word which is one of
`alias‘, `keyword‘, `function‘, `builtin‘, `file‘ or `‘, if NAME is
an
alias, shell reserved word, shell function, shell
builtin, disk file,
or unfound,
respectively.
If the -p flag
is used, `type‘ either returns the name of the disk
file
that would be executed, or nothing if `type -t NAME‘ would
not
return
`file‘.
If the -a flag is
used, `type‘ displays all of the places that contain
an
executable named `file‘. This includes aliases, builtins,
and
functions, if and only if the -p flag is not also
used.
The -f flag suppresses
shell function lookup.
The -P
flag forces a PATH search for each NAME, even if it is an
alias,
builtin, or function, and returns the name of the
disk file that would
be executed.
typeset: typeset
[-afFirtx] [-p] name[=value] ...
Obsolete. See
`declare‘.
[root@new55 ~]#
[root@new55 ~]# type -a cd
cd is a shell
builtin
[root@new55 ~]# type -a pwd
pwd is a shell
builtin
pwd is /bin/pwd
[root@new55 ~]# type -a
time
time is a shell keyword
time is
/usr/bin/time
[root@new55 ~]# type -a date
date is
/bin/date
[root@new55 ~]# type -a which
which is
aliased to `alias | /usr/bin/which --tty-only --read-alias --show-dot
--show-tilde‘
which is /usr/bin/which
[root@new55 ~]# type -a
whereis
whereis is /usr/bin/whereis
[root@new55
~]# type -a whatis
whatis is
/usr/bin/whatis
[root@new55 ~]# type -a
function
function is a shell keyword
[root@new55
~]# type -a ls
ls is aliased to `ls
--color=tty‘
ls is /bin/ls
[root@new55 ~]# type -a
ll
ll is aliased to `ls -l --color=tty‘
[root@new55
~]# type -a echo
echo is a shell builtin
echo is
/bin/echo
[root@new55 ~]# type -a bulitin
-bash:
type: bulitin: not found
[root@new55 ~]# type -a
builtin
builtin is a shell builtin
[root@new55
~]# type -a keyword
-bash: type: keyword: not
found
[root@new55 ~]# type -a command
command is a
shell builtin
[root@new55 ~]# type -a alias
alias
is a shell builtin
[root@new55 ~]# type -a
grep
grep is /bin/grep
[root@new55 ~]#
【1】Blue_Stone‘s OpenWorld Linux中的type命令
【2】山海经 Linux中的type命令
【3】鸟哥的私房菜 Bash shell 的內建命令：
type
【4】阮一峰的网络日志 Linux的五个查找命令
转自：http://codingstandards.iteye.com/blog/831504
原文：http://www.cnblogs.com/youxin/p/3543549.html