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/etc/shells  View the shell--echo under the system$SHELL    View the shell that the current user is running

Shell can run child shell--type/bin/dash     execution childShell at command line--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 file user attributes and user group properties must be modified with a user with permission --note ② when the modified file is a directory file, use '-R' parameter, which indicates recursive traversal of the sub-file modification, where the '-R' is capitalized 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 -- use similar to Chown, but only for modifying user groups (two notes are the same)--Example: Chgrp root abc-r

umask-- View the default permission bit for creating files, directories -- command line type umask    print 0002  0002 is octal, control umask permission bit table, when Umask is 0 o'clock, The corresponding file permissions are 6, converted to binary that is 110, the corresponding directory permission 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 rights, then 111 that is rwx  when Umask is 0002, The permission to represent 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-s source file generation file 122     Create a hard connection  123     Creating a soft connection --NOTE: You cannot create a connection for a directory file

Linux Shell Basics