Brother Bird's Linux private dish notes 6------11 Learn Bash

Source: Internet
Author: User
Tags builtin locale

1. Legal shell and/etc/shells functions     shell has multiple versions, including Bourne Shell (SH), C shell, K-Shell, tcsh, etc. Normally Linux uses the Bourne Again Shell (Bash), which is the enhanced version of SH       can check/etc/shells to see how many shells are available. Writing a legitimate shell to a/etc/shells file is a way for some of the system's services to check the shells that the user is able to use during the run. When the user logs in, it gets a shell to work, which is recorded in the/etc/passwd file 2.bash Shell function       command memory history, the default command memory function 1000. In the ~/.bash_history file       command completion:tab      alias:alias      Job control, foreground, background (job control, foreground, background)      shell script      wildcard character (Wildcard) 3.bash Built-in command type: View commands from external commands or built-in commands      type [-TPA] name         -T: Display fields are: file, alias, builtin         -P: Displays the full file name when the external command is followed,          -A: In the path defined by path, List all commands that contain name. 4. Variable settings and display unset, echo      variable rules:          variables and variable contents with equals = link   name= "Vbird"           equals can not have space bar           variable name can only be English letters and numbers, the beginning cannot be a number          variable content If there are spaces, use "" or "to expand the variable,               " "in special characters such as $ can be maintained in original features                 ' special characters are only general characters           escape characters \ can be en ter, $, \ etc become general characters.           If there are other commands in a sequence of commands, it can be executed with $ (comand) or comand.           system default variable is usually uppercase, custom variable is lowercase           Cancel variable with unset name5.bash command to open a sub-process s HELL6. Environment variables function      ENV command view the environment variables and common environment variable descriptions           Hoem: Represents the Home folder  CD ~  & nbsp       SHELL: currently used shell          Histsize: Record count           MA IL: Mailbox files read by the system using the Mail command at the time of delivery           PATH: Directory of environment variables           LANG: Language data           random: Random number      set command View all variables (environment variables and custom variables)         &NBSP ; PS1 (prompt setting)           $ (This shell PID): Echo $$         ? (Callback code for previous command)      export: Convert custom variable to environment variable      declare: Can convert environment variable to custom variable 7.locale language variable  /etc/ Default/locale    /ETC/SYSCONFIG/I18N8. Variable keypad reads, arrays and declarations read, array, declare     read [-pt] variable         -P: Follow-up prompt          -T: Number of seconds to wait after the next      DECL is [-AIXR] varibale         -A: Declared array array         -I: declared integer   &NBS P      -x: Declare export environment variable          -r: Set Variable to readonly     var[index]= content     echo "${var[1],${var[2"}} "      recommended ${} Reading array contents 9. Restrictions on file systems and programs: ulimit10. Deletion, substitution, substitution      ${variable# keywords for variable contents}: Array matching keywords from the beginning, deleting the shortest data      ${varibale# #keyword}: Match keywords from the beginning, remove the longest data      ${variable%keyword}    : matches the keyword from the end, Delete the shortest data      ${variable%%keyword}    : from the tailStart matching keywords, remove the longest data      ${variable/old str/new str}: Match the contents of the variable to the old string, replace the first one with the new     ${ Variable//old str/new str}: Replace All
     #: The one with the shortest replacement text      ##: The longest match for the replacement text 11. Test and content substitution for variables                                   &NBSP;STR no setup      str= "        &NBSP;STR set to non-empty      var=${str-expr}         & nbsp;var=expr          var=          var= $str      var=${s TR:-EXPR}          var=expr        var=expr     var= $str   &nbs P &NBSP;VAR=${STR+EXPR}          var=            var=expr   &NBS P   var=expr     var=${str:+expr}          var=         &NB Sp    var=          var=expr     var=${str=expr}    str=expr, var=expr  str unchanged, var= &nbsp  str unchanged, var= $str      var=${str:=expr}   str=expr,var=expr  str=expr,var=expr   Str invariant, var= $str      var=${str?expr}     expr output to stderr    var=       &NBS P  var=str     var=${str:?expr}     expr output to stderr  expr output to stderr  var= Str12. Historical aliases alias unalias          ~/.BASHRC files set 13.bash operating environment       path and command lookup order:           1. Execute commands in absolute relative path           2. The command is found by alias execution       &NB Sp   3. Executed by bash built-in builtin command           4. The first command found in $path order is executed.      bash Login with welcome information/ETC/ISSUE,/ETC/MOTD./etc/update-motd.d in Ubuntu 00-header  10- Help-text file in 14.bash config file       read process with login shell:/etc/profile------------>~/.bash_ Profile--------------> Start bash Operations                         &NBSP ;                ----->/etc/inputrc          -------->~/.b ashrc                                &NBSP ;        ----->/etc/profile.d/*.sh                  &NB Sp                          ,         &NB Sp      --->/etc/sysconfig/i18n      read ~/.bashrc     /when Nologin-bash is obtained Data defined in ETC/BASHRC:          Umask values according to the different UID.           PS1 values based on different UID requirements.           call/etc/profile.d/*.sh settings 15. Terminal Environment Configuration stty,set16. wildcard characters and special symbols       wildcard characters:           *     represents 0 to infinity any character          ?     represents an arbitrary character         &NBSP []     represents a character within brackets           [-]     represents a character within a bracket range           [^]     Non-bracket characters       Special symbols:          #     comments   & nbsp           escape           |     Pipelines          ;     Command delimiter           ~     User home folder           $   &N Bsp Variable           &     Job control, background run          !     non          /          directory symbols         &NBS P >,>>     Data flow redirection, replacement   cumulative           <,<<     Stream redirection           "    no variable substitution function          " "    variable substitution function &nbsp ;     &NBsp   "    commands that can be executed, also available in $ ()           ()     Middle for child shell start and end     &N Bsp     {}     middle command block combination 17. REDIRECT       standard input   code 0, using <,<<      StdOut     Code 1, using >,>>     stderr     code 2, using 2>,2>>    & nbsp, if the error and correct output to the same file, with           find/home-name. BASHRC >list 2>&1           find/home-name. BASHRC &>list       If you discard some of the error messages, use the 2>/dev/ Null18. Pipeline commands       pick command:cut,grep      Sort command:sort,wc,uniq      bidirectional redirection:tee      Character conversion command:tr,col,join,paste,expand      Cut command:split      parameter substitution:xargs      About-: stdout of the previous command as stdin of the current command

Brother Bird's Linux private dish notes 6------11 Learn Bash

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.