Text Processing command series--head and tail

Head: View the contents of the file, the first 10 lines of content are displayed by default.

Tail: View the contents of a file, which shows the following 10 lines by default.

Head and tail if you want to display the contents of the specified number of rows, you can use the-n option.

Option Description: Head-n Number: Displays the contents of the previous number line. Head-c number-bytes: Displays the contents of the preceding number of bytes. You can use units such as K. such as Head-c 5k Display the contents of the top 5 K. Head-n-number: Displays all rows except for the following number lines.

Tail-n Number: Displays the contents of the following number rows. Tail-c number-bytes: Displays the contents of the following number of bytes. Tail-n +number: Displays the contents of all rows starting from the number line. TAIL-F FileName: Constant monitoring of changes in the content of a file, often used to view log files. Tail-f FileName: The function is the same as tail-f, but when a monitored file is moved, tail-f retries.

Example:

[[email protected] ~]# cat -n /etc/services | head      1# /etc/services:     2#  $Id:  services,v 1.48 2009/11/ 11 14:32:31 ovasik exp $     3#     4#  network services, internet style     5# iana services  version: last updated 2009-11-10     6#      7# note that it is presently the policy of iana to  assign a single well-known     8# port number for  both TCP and UDP; hence, most entries here have two  ENTRIES     9# EVEN IF THE PROTOCOL DOESN ' T support  udp operations.    10# updated from rfc 1700,  "Assigned Numbers"   ( october 1994).   not all ports[[email protected] ~]#

[[email protected] ~]# cat -n /etc/services | tail 10765nimgtw           48003/udp                # Nimbus Gateway 107663gpp-cbsp        48049/tcp                # 3gpp cell broadcast service protocol 10767isnetserv        48128/tcp                # image systems network services 10768isnetserv        48128/udp                # Image Systems Network Services 10769blp5             48129/tcp                # Bloomberg locator 10770blp5             48129/udp                # Bloomberg locator 10771com-bardac-dw   48556/tcp                # com-bardac-dw  10772com-bardac-dw   48556/udp                # com-bardac-dw 10773iqobject         48619/tcp                # iqobject 10774iqobject        48619/udp                # iqobject[[email protected] ~]# 

Head-n-number and Tail-n +number usage: [[email protected] ~]# Cat-n/etc/issue | Head-n-2 1 CentOS release 6.5 (Final) [[email protected] ~]# [[email protected] ~]# Cat-n/etc/issue | Tail-n +2 2 Kernel \ r on an \m 3[[email protected] ~]#

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Text Processing command series--head and tail