shell常见示例

1、列出当前系统上所有已经登录的用户的用户名，注意：同一个用户登录多次，则只显示一次即可。

            >>> who | awk '{print $1}' | uniq

2、取出最后登录到当前系统的用户的相关信息。

            >>> last | head -1

                    user03  pts/2        10.14.5.119      Mon Sep  3 09:40  still logged in

            >>> lastlog | tail -1

                    user03          pts/2    10.14.5.119      Mon Sep  3 09:40:13 +0800 2018         

3、取出当前系统上被用户当作其默认shell的最多的那个shell。

            >>> awk -F: '{print $NF}' /etc/passwd | uniq -c | sort -rn | head -1

                    10 /sbin/nologin

4、将/etc/passwd中的第三个字段数值最大的后10个用户的信息全部改为大写后保存至/tmp/maxusers.txt文件中。

            >>>cat /etc/passwd | sort -k 3 -rn -t: | head -11 | tail -10 | tr "a-z" "A-Z" > /tmp/maxusers.txt

            >>>cat /tmp/maxusers.txt

                    FEDORA:X:4002:4002:FEDORA CORE:/HOME/FEDORA:/BIN/TCSH

                    GENTOO:X:4001:4001::/VAR/TMP/GENTOO:/BIN/BASH

                    USER01:X:3000:3000:TEST USER:/HOME/USER01:/BIN/BASH

                    SLACKWARE:X:2002:2016::/HOME/SLACKWARE:/BIN/TCSH

                    MAGEIA:X:1100:1100::/HOME/LINUX:/BIN/BASH

                    VN0ECO6:X:1004:1004::/HOME/VN0ECO6:/BIN/BASH

                    USER02:X:1003:1003::/HOME/USER02:/BIN/BASH

                    ZABBIX:X:1001:1001::/HOME/ZABBIX:/BIN/BASH

                    APPUSER:X:1000:1000:APPUSER:/HOME/APPUSER:/BIN/BASH

                    POLKITD:X:999:997:USER FOR POLKITD:/:/SBIN/NOLOGIN

5、取出当前主机的IP地址，提示：对ifconfig命令的结果进行切分。

            >>>ifconfig | grep inet | grep -v 'inet6' | awk '{print $2}'

                    10.233.49.250

                    127.0.0.1

6、列出/etc目录下所有以.conf结尾的文件的文件名，并将其名字转换为大写后保存至/tmp/etc.conf文件中。

>>> ls /etc/*.conf | tr {a-z} {A-Z} > /tmp/etc.conf

>>> cat /tmp/etc.conf

        /ETC/ASOUND.CONF

        /ETC/CHRONY.CONF

        /ETC/DRACUT.CONF

        /ETC/E2FSCK.CONF

        /ETC/FPRINTD.CONF

.............................................

7、显示/var目录下一级子目录或文件的总个数。

            >>> ll /var/* -d | wc -l

                    22

8、取出/etc/group文件中第三个字段数值最小的10个组的名字。

            >>>cat /etc/group | sort -k 3 -rn -t: | tail -10 | cut -d: -f1

                    kmem

                    mem

                    lp

                    disk

                    tty

                    adm

                    sys

                    daemon

                    bin

                    root

9、将/etc/fstab和/etc/issue文件的内容合并为同一个内容后保存至/tmp/etc.test文件中。

            >>>cat /etc/fstab /etc/issue > /tmp/etc.test

            >>> cat /tmp/etc.test

                     # /etc/fstab

                    # Created by anaconda on Thu Apr 26 17:20:24 2018

                    # Accessible filesystems, by reference, are maintained under '/dev/disk'

                    # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

                    /dev/mapper/centos-root /                      xfs    defaults        0 0

                    UUID=31ed9270-a12c-4aad-884e-4d207c290651 /boot                  xfs    defaults        0 0

                    /dev/mapper/centos-home /home                  xfs    defaults        0 0

                    /dev/mapper/centos-swap swap                    swap    defaults        0 0

                    \S

                    Kernel \r on an \m