bash基本知识

时间：2006-08-19 来源：sosogh

bash基本知识一.Changing working directories 前提条件： Each command assumes that your working directory is /home/cam just before the command is executed

Command	New working directory
cd book	/home/cam/book
cd book/wonderland	/home/cam/book/wonderland
cd ~/book/wonderland	/home/cam/book/wonderland
cd /usr/lib	/usr/lib
cd ..	/home
cd ../gryphon	/home/gryphon
cd ~gryphon	/home/gryphon

2.Pathname Expansion pathname expansion wildcards will expand to files and directories that exist Pathname Expansion的作用：将这些wildcards等扩展为“存在的目录或者文件”

Table 1-2. Basic wildcards

Wildcard	Matches
?	Any single character
*	Any string of characters
[set]	Any character in set
[!set]	Any character not in set 这个还可以表示成[^set]，但是 [!set]不能用在grep或者sed的regex中，因为在grep等的regex中[!set]中的！是一个“表面字符”，而不是一个“特殊字符”

Table 1-3. Using the * wildcard

Expression	Yields
fr*	frank fred
*ed	ed fred
b*	bob
e	darlene dave ed fred
r	darlene frank fred
*	bob darlene dave ed frank fred
d*e	darlene dave
g*	g（当号匹配不当任何东西时候，shell会直接把g*这2个字符送到cmd中去）

如：假如你现在的目录下有个文件叫good.txt，如果你输入vi good.txt 那么vi会打开good.txt这个文件如果你的现在的目录下没有g字符开头的文件，那么vi就直接新建一个“名字叫g*”的文件 3.Brace Expansion brace expansion expands to an arbitrary string brace expansion作用：扩张为“一个字符串” 例如： echo begin{1,2,3}end 相等与 echo begin1end begin2end begin3end {}还可以内嵌 b{ar{d,n,k},ed}s →→→→→→ bards, barns, barks, and beds 以下要在bash的3.0版本以后才有 This form of brace expansion is not available in bash prior to Version 3.0. {2..5} →→→→→→ 2 3 4 5 {d..h} →→→→→→ d e f g h 4.Background I/O （1）If a background job produces screen output, the output will just appear on your screen. If you are running a job in the foreground that produces output too, then the output from the two jobs will be randomly (and often annoyingly) interspersed 如果把一个job放在Background 中，而且这个jobs会产生screen output，然后有在当前运行另外一个job，，而且这个job也会产生screen output，那么这2个jobs的output就会随机穿插的显示在stdout中 5.使用bash的help命令 help命令是bash的help命令，而不是其他cmd（工具的）直接输入help会看到bash内建命令和其他一些信息 help bash内建功能查看bash内建功能的信息如：help if help . help % help exit

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