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第五章 Working With Commands
1. type→Indicate how a command name is interpreted
辨識是什麼樣的命令
範例：mate@404040456debian:~$ type --help
bash: type: --：無效選項
type: usage: type [-afptP] name [name ...]
mate@404040456debian:~$ mkdir --help
Usage: mkdir [OPTION]... DIRECTORY...
Create the DIRECTORY(ies), if they do not already exist.
Mandatory arguments to long options are mandatory for short options too.
-m, --mode=MODE set file mode (as in chmod), not a=rwx - umask
-p, --parents no error if existing, make parent directories as needed
-v, --verbose print a message for each created directory
-Z set SELinux security context of each created directory
to the default type
--context[=CTX] like -Z, or if CTX is specified then set the SELinux
or SMACK security context to CTX
--help 顯示此求助說明並離開
--version 顯示版本資訊並離開
2. which→Display which executable program will be executed
顯示會執行哪個可執行程式
3. help→Get help for shell builtins
得到shell 內部命令的幫助文檔
範例：mate@404040456debian:~$ help type
type: type [-afptP] name [name ...]
Display information about command type.
For each NAME, indicate how it would be interpreted if used as a
command name.
Options:
-a display all locations containing an executable named NAME;
Includes aliases, builtins, and functions, if and only if
the `-p' option is not also used
-f suppress shell function lookup
-P force 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
-p returns either the name of the disk file that would be executed,
or nothing if `type -t NAME' would not return `file'.
-t output 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 not
found, respectively
Arguments:
NAME Command name to be interpreted.
Exit Status:
Returns success if all of the NAMEs are found; fails if any are not found.
4. man→Display a command's manual page
顯示命令手冊頁
範例：mate@404040456debian:~$ man ls
LS(1) User Commands
LS(1)
NAME
ls - list directory contents
SYNOPSIS
ls [OPTION]... [FILE]...
DESCRIPTION
List information about the FILEs (the current directory by default). Sort
entries alphabetically if none of -cftuvSUX nor --sort is specified.
Mandatory arguments to long options are mandatory for short options too.
-a, --all
do not ignore entries starting with .
-A, --almost-all
do not list implied . and ..
5. apropos→Display a list of appropriate commands
顯示一適合的命令清單
範例：mate@404040456debian:~$ apropos ls
aconnect (1) - ALSA sequencer connection manager
add-shell (8) - add shells to the list of valid login shells
alsactl (1) - advanced controls for ALSA soundcard driver
6. whatis→Display a very brief description of a command
顯示一個命令的簡潔描述
7. info→Display a command's info entry
顯示命令info
8. alias→Create an alias for a command
創造命令的別名
一、Shall指令裡命令有哪些(四種)？
1. An executable program.
一個可執行程式，就像我們所看到的位於目錄/usr/bin中的檔案一樣。
屬於這一類的程式，可以編譯成二進位檔案，也可以是由指令碼語言寫成的程式。
2. A command built into the shell itself.
一個內建於shell自身的命令，bash支持若干種命令。
內部命令叫做shell builtins。
3. A shell function.
一個shell函數。
4. An alias.
一個命令別名。可以定義屬於自己的命令，建立在其它命令之上。
二、上課目前學過的指令：
mate@404040456debian:~$ type date 可執行程式
date is /bin/date
mate@404040456debian:~$ type cal 可執行程式
cal is /usr/bin/cal
mate@404040456debian:~$ type df 可執行程式
df is /bin/df
mate@404040456debian:~$ type free 可執行程式
free is /usr/bin/free
mate@404040456debian:~$ type exit shell 本身的命令
exit is a shell builtin
mate@404040456debian:~$ type pwd shell 本身的命令
pwd is a shell builtin
mate@404040456debian:~$ type cd shell 本身的命令
cd is a shell builtin
mate@404040456debian:~$ type ls 命名別名
ls is aliased to `ls --color=auto'
mate@404040456debian:~$ type file 可執行程式
file is /usr/bin/file
mate@404040456debian:~$ type less 可執行程式
less is /usr/bin/less
mate@404040456debian:~$ type cp 可執行程式
cp is /bin/cp
mate@404040456debian:~$ type mv 可執行程式
mv is /bin/mv
mate@404040456debian:~$ type mkdir 可執行程式
mkdir is /bin/mkdir
mate@404040456debian:~$ type rm 可執行程式
rm is /bin/rm
mate@404040456debian:~$ type ln 可執行程式
ln is /bin/ln
共有15種指令，分為三種資料型態，為 可執行程式、命名別名、 shell 本身的命令
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