【2018.04.20学习笔记】【linux基础知识8.1-8.5】

8.1 shell介绍

shell是一种命令解释器，用于接收用户指令与操作系统交互；

他有特定的语法：例如逻辑判断、循环语句等。

每个系统用户都有自己的shell，CentOS默认的Shell是 -bash（bourne Agin Shell）

系统还有zsh、ksh等。

Connecting to 192.168.87.130:22...
Connection established.
To escape to local shell, press 'Ctrl+Alt+]'.

Last login: Fri Apr 20 00:00:10 2018 from 192.168.87.1
[root@lgs-01 ~]# shell
-bash: shell: 未找到命令

8.2 命令历史

linux系统会记录用户输入过的历史命令。

查看命令的历史记录：history 命令，默认存储1000条命令历史

[root@lgs-01 ~]# history
 #节省部分显示 
 976  rm -rf /var/cache/yum/x86_64/7/base/packages/zziplib-0.13.62-5.el7.x86_64.rpm 
  977  ls -l /var/cache/yum/x86_64/7/base/packages/
  978  yum reinstall -y zziplib --downloadonly
  979  ls -l /var/cache/yum/x86_64/7/base/packages/
  980  cd /usr/local/src/
  981  ls
  982  wget http://cn2.php.net/distributions/php-7.1.6.tar.bz2
  983  ls -l php-7.1.6.tar.bz2 
  984  tar jxvf php-7.1.6.tar.bz2 
  985  ls
  986  cd php-7.1.6
  987  ls
  988  ./configure --prefix=/usr/local/php7 --with-apxs2=/usr/local/apache2.4/bin/apxs --with-config-file-path=/usr/local/php7/etc --with-pdo-mysql=/usr/local/mysql/ -with-mysqli=/usr/local/mysql/bin/mysql_config --with-libxml-dir --with-gd --with-jpeg-dir --with-png-dir --with-freetype-dir --with-iconv-dir --with-zlib-dir --with-bz2 --with-openssl --with-mcrypt --enable-soap --enable-gd-native-ttf --enable-mbstring --enable-sockets --enable-exif
  989  echo $?
  990  make
  991  echo $?
  992  make install
  993  echo $?
  994  /usr/local/apache2.4/bin/apachectl -M
  995  ls -l /usr/local/apache2.4/modules/libphp7.so 
  996  init 0
  997  shell
  998  history

history的历史是记录在 /root/.bash_history里：

[root@lgs-01 ~]# ls -l /root/.bash_history 
-rw-------. 1 root root 23650 4月  20 01:11 /root/.bash_history

清除命令历史：history -c

默认记录1000条命令历史，可以修改配置文件/etc/profile里的HISTSIZE参数：

[root@lgs-01 ~]# echo $HISTSIZE 
1000
[root@lgs-01 ~]# cat /etc/profile
# /etc/profile

# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc

# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.

pathmunge () {
    case ":${PATH}:" in
        *:"$1":*)
            ;;
        *)
            if [ "$2" = "after" ] ; then
                PATH=$PATH:$1
            else
                PATH=$1:$PATH
            fi
    esac
}


if [ -x /usr/bin/id ]; then
    if [ -z "$EUID" ]; then
        # ksh workaround
        EUID=`/usr/bin/id -u`
        UID=`/usr/bin/id -ru`
    fi
    USER="`/usr/bin/id -un`"
    LOGNAME=$USER
    MAIL="/var/spool/mail/$USER"
fi

# Path manipulation
if [ "$EUID" = "0" ]; then
    pathmunge /usr/sbin
    pathmunge /usr/local/sbin
else
    pathmunge /usr/local/sbin after
    pathmunge /usr/sbin after
fi

HOSTNAME=`/usr/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
    export HISTCONTROL=ignoreboth
else
    export HISTCONTROL=ignoredups
fi

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL

# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`/usr/bin/id -gn`" = "`/usr/bin/id -un`" ]; then
    umask 002
else
    umask 022
fi

for i in /etc/profile.d/*.sh ; do
    if [ -r "$i" ]; then
        if [ "${-#*i}" != "$-" ]; then 
            . "$i"
        else
            . "$i" >/dev/null
        fi
    fi
done

unset i
unset -f pathmunge

加入变量HISTTIMEFORMAT="%Y/%m/%d %H:%M:%S"，可以显示命令执行的时间

修改配置文件后，source /etc/profile 重新加载才生效

[root@lgs-01 ~]# cat /etc/profile
# /etc/profile

# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc

# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.
#节省部分内容
HOSTNAME=`/usr/bin/hostname 2>/dev/null`
HISTSIZE=1000
HISTTIMEFORMAT="%Y/%m/%d %H:%M:%S"
[root@lgs-01 ~]# source /etc/profile
[root@lgs-01 ~]# history
  995  2018/04/20 13:33:01ls -l /usr/local/apache2.4/modules/libphp7.so 
  996  2018/04/20 13:33:01init 0
  997  2018/04/20 14:20:48shell
  998  2018/04/20 14:23:11history
  999  2018/04/20 14:25:22historyls -l /etc/.bash_history
 1000  2018/04/20 14:25:27ls -l /etc/.bash_history
 1001  2018/04/20 14:25:46ls -l /root/.bash_history 
 1002  2018/04/20 14:27:11cat /root/.bash_history 
 1003  2018/04/20 14:27:41vim /root/.bash_history 
 1004  2018/04/20 14:31:30echo $HISTSIZE 
 1005  2018/04/20 14:32:03cat /etc/profile
 1006  2018/04/20 14:35:16vim /etc/profile
 1007  2018/04/20 14:36:43source /etc/profile
 1008  2018/04/20 14:36:46ls
 1009  2018/04/20 14:36:55history

执行上一条命令：!!

[root@lgs-01 ~]# !!
ls
123.zip                                b                                          mesa-libGL-devel-17.0.1-6.20170307.el7.x86_64.rpm
1.txt.bak                              c                                          mesa-libGLU-9.0.0-4.el7.x86_64.rpm

执行命令历史里的第几条命令：!n ，n是数字

 1010  2018/04/20 14:39:18 cat /etc/profile
 1011  2018/04/20 14:40:04 source /etc/profile
 1012  2018/04/20 14:40:45 ls
 1013  2018/04/20 14:41:54 history
[root@lgs-01 ~]# !1011
source /etc/profile

执行最近以某字符内容开头的命令：!echo

 1004  2018/04/20 14:31:30 echo $HISTSIZE 
 1005  2018/04/20 14:32:03 cat /etc/profile
 1006  2018/04/20 14:35:16 vim /etc/profile
 1007  2018/04/20 14:36:43 source /etc/profile
 1008  2018/04/20 14:36:46 ls
 1009  2018/04/20 14:36:55 history
 1010  2018/04/20 14:39:18 cat /etc/profile
 1011  2018/04/20 14:40:04 source /etc/profile
 1012  2018/04/20 14:40:45 ls
 1013  2018/04/20 14:41:54 history
[root@lgs-01 ~]# !1011
source /etc/profile
[root@lgs-01 ~]# !echo
echo $HISTSIZE 
1000

8.3 命令补全和别名

linux系统提供了命令输入的补全功能，提高用户输入命令的效率。

需要安装：bash-completion

当输入命令、文件或者目录的开头部分字符串的时候：按tab补全：

按一下tab：当开头字符串只有一个命令、文件或者目录匹配的时候，按一下tab即可补全

# [root@lgs-01 ~]# logo 此处按一下tab，即可补全命令 logout
[root@lgs-01 ~]# logout

按两下tab：当开头字符串不止一个命令、文件或者目录匹配的时候，按两下tab可以列出所有该开头字符串的命令、文件或者目录，然后再继续根据提示输入后续字符即可。

[root@lgs-01 ~]# log
logger     login      loginctl   logname    logout     logrotate  logsave

当一条命令很长的时候，还可以给命令起别名，提高输入效率

用alias命令：例如ls命令，是有带颜色显示选项的ls命令取别名而来

[root@lgs-01 ~]# which ls
alias ls='ls --color=auto'
	/usr/bin/l
[root@lgs-01 ~]# alias restartnet='systemctl restart network.service '
[root@lgs-01 ~]# res
reset       resize2fs   resizecons  resizepart  restartnet  restorecon  
[root@lgs-01 ~]# restartnet 
[root@lgs-01 ~]# which restartnet
alias restartnet='systemctl restart network.service '
	/usr/bin/systemctl

查看系统所有的别名：

[root@lgs-01 ~]# alias
alias cp='cp -i'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls --color=auto'
alias mv='mv -i'
alias restartnet='systemctl restart network.service '
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'

在用户家目录下的/.bashrc 配置文件里定义了部分系统的alias别名，剩下的在

/etc/profile.d/ 目录下的脚本文件

[root@lgs-01 ~]# cat /root/.bashrc 
# .bashrc

# User specific aliases and functions

alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

# Source global definitions
if [ -f /etc/bashrc ]; then
	. /etc/bashrc
fi
[root@lgs-01 ~]# ls /etc/profile.d/
256term.csh  colorgrep.csh  colorls.csh  gnome-ssh-askpass.csh  lang.csh  less.csh  vim.csh  which2.csh
256term.sh   colorgrep.sh   colorls.sh   gnome-ssh-askpass.sh   lang.sh   less.sh   vim.sh   which2.sh

8.4 命令的通配符

任意个字符或0个：*

[root@lgs-01 ~]# ls *.bak
1.txt.bak  2_hard.txt.bak  2.txt.bak

[root@lgs-01 ~]# ls 333*.tar
333.tar

单个字符：

[root@lgs-01 ~]# ls 33?.tar
333.tar

[ ] 中括号范围内的单个字符

[root@lgs-01 ~]# ls *.txt
k.txt  zb.txt
[root@lgs-01 ~]# ls [a-zA-Z].txt
k.txt

[ ] 中括号里选取某单个字符

[root@lgs-01 ~]# ls *.txt
k.txt  w.txt  zb.txt
[root@lgs-01 ~]# ls [lkw].txt
k.txt  w.txt

{ } 大括号里的一个字符段，以逗号分隔

[root@lgs-01 ~]# ls *.txt
abcd.txt  ape.txt  k.txt  los.txt  w.txt  zb.txt
[root@lgs-01 ~]# ls {los,k,sss,ape}.txt
ls: 无法访问sss.txt: 没有那个文件或目录
ape.txt  k.txt  los.txt

8.5 输入输出重定向

输出重定向，覆盖原文件的内容： >

[root@lgs-01 ~]# echo 1234 >w.txt 
[root@lgs-01 ~]# cat w.txt 
1234
[root@lgs-01 ~]# echo 0008 >w.txt 
[root@lgs-01 ~]# cat w.txt 
0008

追加重定向，只追加内容，不覆盖：>>

[root@lgs-01 ~]# cat w.txt 
0008
[root@lgs-01 ~]# echo 99999 >>w.txt 
[root@lgs-01 ~]# cat w.txt 
0008
99999

错误信息输出重定向： 2>

[root@lgs-01 ~]# laaaa
-bash: laaaa: 未找到命令
[root@lgs-01 ~]# laaaa 2>k.txt 
[root@lgs-01 ~]# cat k.txt 
-bash: laaaa: 未找到命令

错误信息追加重定向：2>>

[root@lgs-01 ~]# laaaa 2>k.txt 
[root@lgs-01 ~]# cat k.txt 
-bash: laaaa: 未找到命令
[root@lgs-01 ~]# kkkkk 2>>k.txt 
[root@lgs-01 ~]# cat k.txt 
-bash: laaaa: 未找到命令
-bash: kkkkk: 未找到命令

正确与错误输出重定向： &>

[root@lgs-01 ~]# ls *.txt 2>k.txt abcccc.txt &>k.txt 
[root@lgs-01 ~]# cat k.txt 
ls: 无法访问abcccc.txt: 没有那个文件或目录
abcd.txt
ape.txt
k.txt
los.txt
w.txt
zb.txt

也支持正确与错误追加重定向： &>>

正确与错误输出分开重定向：

[root@lgs-01 ~]# cat w.txt 
0008
99999
[root@lgs-01 ~]# cat k.txt 
111
[root@lgs-01 ~]# ls *.txt ppp.txt >w.txt 2>k.txt 
[root@lgs-01 ~]# cat w.txt 
abcd.txt
ape.txt
k.txt
los.txt
w.txt
zb.txt
[root@lgs-01 ~]# cat k.txt 
ls: 无法访问ppp.txt: 没有那个文件或目录

输入重定向：< 把右边的文件内容 输入给 左边的命令，左边只能是命令

[root@lgs-01 ~]# cat w.txt 
abcd.txt
ape.txt
k.txt
los.txt
w.txt
zb.txt
[root@lgs-01 ~]# wc -l <w.txt 
6