这三个”剑客”的特长。
    grep 更适合单纯的查找或匹配文本
    sed 更适合编辑匹配到的文本
    awk 更适合格式化文本，对文本进行较复杂格式处理

    http://www.zsythink.net/archives/1336

    awk ‘{print $0}’ 

    1. [root@n9e ~]# awk '{print $0}' /etc/resolv.conf 
    2. # Generated by NetworkManager
    3. options rotate
    4. domain  boccfc.com
    5. search  test.boccfc.com boccfc.com
    6. nameserver 10.182.211.82 
    7. nameserver 10.182.211.83 
    8. nameserver 114.114.114.114
    9. nameserver 1.1.1.1
    10. nameserver 8.8.8.8
    13. [root@n9e ~]# awk '{print $1}' /etc/resolv.conf 
    14. #
    15. options
    16. domain
    17. search
    18. nameserver
    19. nameserver
    20. nameserver
    21. nameserver
    22. nameserver
    25. [root@n9e ~]# awk '{print $2}' /etc/resolv.conf 
    26. Generated
    27. rotate
    28. boccfc.com
    29. test.boccfc.com
    30. 10.182.211.82
    31. 10.182.211.83
    32. 114.114.114.114
    33. 1.1.1.1
    34. 8.8.8.8
    35. [root@n9e ~]#
    1. [root@n9e ~]# df -TH
    2. Filesystem              Type      Size  Used Avail Use% Mounted on
    3. /dev/mapper/centos-root xfs        48G  4.6G   43G  10% /
    4. devtmpfs                devtmpfs  2.0G     0  2.0G   0% /dev
    5. tmpfs                   tmpfs     2.0G     0  2.0G   0% /dev/shm
    6. tmpfs                   tmpfs     2.0G  9.0M  2.0G   1% /run
    7. tmpfs                   tmpfs     2.0G     0  2.0G   0% /sys/fs/cgroup
    8. /dev/sda1               xfs       1.1G  150M  914M  15% /boot
    9. tmpfs                   tmpfs     396M     0  396M   0% /run/user/700
    10. [root@n9e ~]# df -TH | awk '{print $5}'
    11. Avail
    12. 43G
    13. 2.0G
    14. 2.0G
    15. 2.0G
    16. 2.0G
    17. 914M
    18. 396M
    19. [root@n9e ~]#
    1. [chroot@n9e ~]$ awk -F":" '{ print $1 }' /etc/passwd |head
    2. root
    3. bin
    4. daemon
    5. adm
    6. lp
    7. sync
    8. shutdown
    9. halt
    10. mail
    11. operator
    12. [chroot@n9e ~]$