Bash Shell Foundation feature theory + case study

1. Command history:

Environment variables:

Histfile: Number of records in the command history

Histsize:~/.bash.history

Histfilesize: The number of history records in a command history file

History: Default display of 10 records

History-n: Show post n history

history-d N: Delete nth history

History-c: Delete all history

History-a: Manually append the history command in the current session buffer to the history file

！ N: Execute nth command repeatedly

!! : Executes the previous command repeatedly

! Add the first few letters of the command: Repeat the last command that starts with these letters

Control how the Command history is recorded:

Environment variable: Histcontrol:

Ignoredups: Ignore consecutive repeated commands

Ignorespace: Ignore commands that begin with a space

Ignoreboth:ignoredups,ignorespace

[[email protected] ~]# history                          //View command history, display 10 history by default    28  history   29  ls   30   history | more   31  history   32  history |  more   33  ls   34  cd   35   ls   36  cd /.bash.hisory   37  history[[email  protected] ~]# history 5                        //See the last 5 commands history    34   cd   35  ls   36  cd /.bash.hisory    37  history   38  history 5[[email protected] ~]# history -d 36                    // Delete 36th command History,[[email protected] ~]# history 5                        //See again, Discovery has been removed    35  ls   36  history   37   history 5   38  history -d 36   39   history 5[[email protected] ~]# history -c                       //Delete all history [email  protected] ~]# history   31  history[[email protected] ~]#  history -a[[email protected] ~]# [[email protected] ~]# cd /[[email protected] /]#  ls123  boot   dev   lib          media  proc  selinux  tmp  varabc  data    etc   lib64       mnt     Root  srv      usr  xxlbin  data1  home   lost+found  opt    sbin  sys       uzz[[email protected] /]# cd [[email protected] ~]# ls12       anaconda-ks.cfg     -n                               uzz123     ett.txt              oldboy                          xxl123456  install.log          oldboy.txt                      xxl.txtabc      install.log.syslog  session192.168.80.1280320.log[[email protected] ~]# history    31  history   32  history -a   33   cd /   34  ls   35  cd    36   ls   37  history[[email protected] ~]# !33                               //repeating 33rd Historical Command cd /[[email protected] /]# cd[[email protected]  ~]# ls12      anaconda-ks.cfg     -n                               uzz123     ett.txt              oldboy                           xxl123456  install.log         oldboy.txt                       xxl.txtabc     install.log.syslog  session192.168.80.1280320.log[[email  protected] ~]# !!                                //repeatedly executes the previous command ls12       anaconda-ks.cfg     -n                               uzz123     ett.txt              oldboy                          xxl123456   install.log         oldboy.txt                      xxl.txtabc      install.log.syslog  session192.168.80.1280320.log[[email protected] ~]# ! c                               //repeatedly executes the last command preceded by C cd[[email  Protected] ~]# [[email protected] ~]# history    2  cd  /    3  ls    4  cd      5  ls    6  history    7  cd  /    8  cd    9  ls   10   cd   11  history[[email protected] ~]# ls12       anaconda-ks.cfg     -n                              uzz123      ett.txt              oldboy                          xxl123456  install.log          oldboy.txt                      xxl.txtabc      install.log.syslog  session192.168.80.1280320.log[[email protected] ~]# ls12       anaconda-ks.cfg     -n                               uzz123     ett.txt              oldboy                          xxl123456  install.log          oldboy.txt                      xxl.txtabc      install.log.syslog  session192.168.80.1280320.log[[email protected] ~]# history                              //The default repeatedly executed commands are not logged     4  CD      5  ls    6  history    7  cd /     8  cd    9  ls   10   cd   11  history   12  ls   13   History[[email protected] ~]#  cd /[[email protected] /]# [[email  protected] /]# history    6  history    7   cd /    8  cd    9  ls    10  cd   11  history   12  ls    13  history   14   cd /   15   history[[email protected] /]# export histcontrol= "Ignorespace"            //setting a command that starts with a space is not logged [[email protected] /]#  cd [[email protected] ~]#  [[Email protected] ~]# history    8  cd    9   ls   10  cd   11  history   12   ls   13  history   14   cd /    15  history   16  export histcontrol= "Ignorespace"     17  history[[email protected] ~]#

2. Command completion and path completion

There are many commands and paths in Linux, and it is unavoidable to forget that the command completion feature provided by the Bash shell compensates for this flaw. Just give the first few letters of the command, bash looks for a file named after the given command name from left to right based on the path defined by the PATH environment variable, and the first time you find the file to run.

Press the TAB key to complete automatically, if not yet complete, you can tap the TAB key, select the command to execute from the options given, or give some hints.

[[email protected] ~]# e                  //Input e press TAB to find a number of commands that begin with E, and then press TAB once to list all e2freefrag              envsubst                eu-objdumpe2fsck                  eqn                     eu-ranlibe2image                 eqn2graph               eu-readelfe2label                 era_check               eu-sizee2undo                  era_dump                eu-stackecho                    era_invalidate         eu-stringsed                       esac                    eu-stripeditdiff                espdiff                 eu-unstripedquota                 ether-wake             evalefibootmgr              ethtool                 exegrep                   eu-addr2line            execeject                   eu-ar                   execstackelif                    eu-elfcmp               exitelinks                  eu-elflint              expandelse                    eu-findtextrel          exportenable                  eu-make-debug-archive  exprenv                     eu-nm                   [[email protected] ~]# echo              //input EC, press ENTER, display echo[[email  protected] ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0  /knocking Tab Completion

This article is from the "Technical Achievement Dream" blog, please be sure to keep this source http://xuxiaoliang.blog.51cto.com/10882951/1921930

Bash Shell Foundation feature theory + case study