Linux Shell Basics

Shell is the core program kernel outside the instruction parser, is a program, colleague is a command language and programming language--shell is a command parser, the user Input command, it to parse.

Shell type     ash,bash,ksh,csh,tcsh--cat qkxue.net/etc/shells  View the Shell--echo under the system $SHELL    view the shell that the current user is running 

Shell can run child shell--at the command line type 1126.www.qixoo.qixoo.com/bin/Dash     Execute sub shell--execute exit in child shell      exit child shell

The default shell under Linux is Bash--bash features: fast, TAB key Auto-completion

chown-- Modify the user attributes and user group properties of the file, directory,chown [user].[ User Group] filename-- Note ① Modify the file user properties and user group properties must be modified with a user with permission-note ② when the modified file is a directory file, use the '-r ' parameter, which means that the recursive traversal of the sub-file is modified, where the ' - R'1. C (executed under root account)--Example: Chown test.test abc-r (Modify directory file)         

chgrp-- Modify the user group properties of a file or directory-the usage is similar to chown, but only used to modify user groups (two notes are the same)-Example: Chgrp root abc-r 

umask-- View Create file, directory default permissions bit-- command line type umask    print 0002  0002 is octal number, control umask permission bit table, when Umask is 0 o'clock, corresponding file permission is 6, converted into binary is 110 , the corresponding directory permissions is 7, the conversion into binary is the 111  file permissions is rwx, corresponding to an octal number, if the file has read and write execution permissions, then is 111 that is rwx  when Umask is 0002, the default file is 664 that is rw-rw-r-- 

ln   (LN)-- Create File connection command-- hard Connect is to copy a file (infrequently used)-- hard connect:    LN source file Generation file    --  A soft connection establishes a soft connection to a file (performing a soft connection is equivalent to executing the file)--Soft Connect:    ln-122123 Creates a soft connection--NOTE: You cannot create a connection for a directory file   

Linux Shell Basics