1.Bash properties
View linux shell script type support
# cat /etc/shells
/bin/sh
/bin/bash
/sbin/nologin
/usr/bin/sh
/usr/bin/bash
/usr/sbin/nologin
/bin/tcsh
/bin/csh
The earliest is called sh sh, also called bsh, from the development of language and B, after the emergence of Csh, which is similar to c language, it emerged on the basis of ksh csh on top, but ksh for the commercial version, Linux systems appear after all, on the development of a bash, a collection of the advantages of sh, csh and ksh's;
Now the latest shell compiler also zsh, but use less;
1. Because Linux is a multi-user, multi-process; so each user application program is the same, but the process is not the same; the same cloning process can be understood as a program; it supports each user their own bash process carried out modified, but the program actually uses bash is the same; how a Linux system to distinguish each user can bash process, which is to be distinguished by the pid;
2 bash features: command line processing: ctrl + a ctrl + e ctrl + u ctrl + l ctrl + w ctrl + k
Ctrl + u Delete the character before the cursor
Ctrl + k Delete the cursor after the character
Ctrl + w a space as a separator, to delete files
Ctrl + r to enter an interactive interface, a command searches recently used (to be input string)
Command History: history
-c
-d 500
-d 500 10
-w // save the file in the home directory .bash_history go, so, even if the restart, clear or -c, the command will be retained history records
Command aliases
alias
unalias
Replace command
$ (Command)
# Echo the same "today is $ (date)" and `` achieve the function
# echo "today is `date`"
``: Forced turn back
Tab key applications
1 fill all orders
2 Completion path
When the need to complement the command or path is not only enter, all options will be displayed;
When too many options to be displayed, it will prompt;
Wildcard file
*
？
[]
^
2. Regular Expressions
\ // turn and character
^ // at the beginning of what
$ // what end
[] // match a character, specified range [] inside, [^ 0-9] represents the negation
[-] // input [-] marked character range
// one arbitrary character
* // 0 or more arbitrary characters
{N, m} // former matches a character or expression to n times m times
{N,} // least n times
{N} // only n times
{, M} // m times at most
Grep "^ \\ $" // filename begins with $
3. extended regular expressions
+ // a character or more than once before the match
? // before a match one character or expression 0 times
| // or
() // Packet