A Linux head command every day

Head and tail are as simple as their name, which is used to display the beginning or end of a number of chunks of text, the head is used to display the beginning of the file to the standard output, and tail to see the end of the file.

1. Command format:

Head [parameters] ... [File]:

2. Command function:

the head is used to display the beginning of the file to the standard output , The default head command prints the first 10 lines of its corresponding file.

3. Command parameters:

- q Hide file names

- v Show file name

-c< bytes > Display bytes

-n< rows > rows displayed

4. usage Examples:

Example 1: Display the first n rows of a file

Command:

head-n 5/etc/fstab

output:

[Begin] 2016/1/7 16:30:21[[email protected] ~]# head -n -5 /etc/fstab  ## /etc/fstab# created by anaconda on thu dec 31 16:39:19  2015## 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/vgLegion-root /                        ext4     defaults,acl        1 1uuid= 4bdd95a5-f81b-4cfd-a446-dc4f5070c2aa /boot                    ext4    defaults         1 2/dev/mapper/vglegion-data /data                    ext4    defaults,acl         1 2/dev/mapper/vgLegion-home /home                    ext4    defaults,acl         1 2/dev/mapper/vgLegion-usr /usr                     ext4     defaults,acl        1 2[[email  protected] ~]# cat -n /etc/fstab      1      2#     3# /etc/fstab     4# created  by anaconda on thu dec 31 16:39:19 2015     5#     6#  Accessible filesystems, by reference, are maintained under  '/dev/disk '      7# see man pages fstab (5),  findfs (8),  mount (8)  and/or blkid (8)  for more info     8#      9/dev/mapper/vgLegion-root /                        ext4     Defaults,acl        1 1    10uuid= 4bdd95a5-f81b-4cfd-a446-dc4f5070c2aa /boot       ext4     defaults        1 2    11/dev/ mapper/vglegion-data /data                   ext4     defaults,acl        1 2     12/dev/mapper/vglegion-home /home                    ext4    defaults,acl         1 2    13/dev/mapper/vgLegion-usr /usr                     ext4     defaults,acl        1 2     14/dev/mapper/vgLegion-swap swap                     swap    defaults,acl         0 0    15tmpfs                    /dev/shm                 tmpfs   defaults         0 0    16devpts                   /dev/pts                 devpts  gid=5,mode=620  0 0     17sysfs                    /sys                     sysfs   defaults         0 0    18proc                     /proc                    proc    defaults         0 0[end] 2016/1/7 16:30:48

Description: The Fstab file contains a total of 18 lines, while the command head-n-5 displays only the first five elements.

Example 2: Displaying the first n bytes of a file

Command:

head-c 20/etc/fstab

Output:

[BEGIN] 2016/1/7 16:33:43[[email protected] ~]# [[email protected] ~]# head-c 20/etc/fstab # #/etc/fstab# Cr[[email Prot Ected] ~]# [END] 2016/1/7 16:34:13

Example 4: Output file except the last n rows of the entire content

Command:

head-n -3/etc/fstab

Output:

[begin] 2016/1/7 16:40:29[[email protected] ~]# cat -n /etc/fstab       1     2#     3# /etc/ fstab     4# created by anaconda on thu dec   3 08:33:34 2015     5#     6# accessible  filesystems, by reference, are maintained under  '/dev/disk '       7# see man pages fstab (5),  findfs (8),  mount (8)  and/or  blkid (8)  for more info     8#     9uuid =8a9c5d3a-e525-4fa2-bcfe-90ced11a0b08 /            ext4    defaults        1 1     10uuid=0167fd91-560f-4baF-bb20-b54d429faf9d /boot       ext4    defaults         1 2    11uuid= 7b81c9d0-9139-4fcb-8700-0173c7ba0f60 swap        swap     defaults        0 0    12tmpfs                     /dev/shm                 tmpfs   defaults        0 0     13devpts                   /dev/pts                 devpts  gid=5,mode=620  0 0    14sysfs                    /sys                     sysfs   defaults         0 0    15proc                     /proc                    proc     defaults        0 0[[email protected]  ~]# head -n -3 /etc/fstab ## /etc/fstab# Created by  Anaconda on thu dec  3 08:33:34 2015## 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#uuid=8a9c5d3a-e525-4fa2-bcfe-90ced11a0b08  /                        ext4    defaults         1 1UUID=0167fd91-560f-4baf-bb20-b54d429faf9d /boot                    ext4     Defaults        1 2uuid=7b81c9d0-9139-4fcb-8700-0173c7ba0f60  swap                     swap    defaults        0  0tmpfs                   /dev/shm                 tmpfs    defaults        0 0[end] 2016/1/7 16:40:39

Note: Except the last three lines are not displayed, all other display

A Linux head command every day