[Add to favorites] Linux tail commands

Linux --- tail command

Linux tail command-used to View File Content

The most basic options are cat, more, and less.
1. If you only want to view the first five lines of the file, you can use the head command, for example:
Head-5/etc/passwd
2. If you want to view the last 10 lines of the file, you can use the tail command, such:
Tail-2/etc/passwd or tail-N 2/etc/passwd
Tail-F/var/log/messages
Parameter-F keeps tail reading the latest content, so that it can be monitored in real time and ended with Ctrl + C!
3. view the middle part of the file. You can use the SED command, for example:
Sed-n'5, 10p'/etc/passwd
In this way, you can only view rows 5th to 10th of the file.

Tail syntax format:
Tail [-F] [-C number |-N number |-M number |-B number |-K number] [file]
Or
Tail [-R] [-N number] [file]
Instructions for use:
The tail command starts
The file specified by the parameter is written to the standard output. If no file is specified, standard input is used. Number variable <br/> specifies the number of units to be written to the standard output.
The value of the number variable can be a positive or negative integer. If the value is preceded by a plus sign, it starts with the file <br
/> The specified number of units starts to write the file to the standard output. If there is a minus sign before the value, the file will be written from the number of units specified at the end of the file <br
/> Standard output. If no + (plus sign) or-(minus sign) exists before the value, read the file starting from the specified unit number at the end of the file.
Main parameters:

-B number reads the specified file from the location of the 512-byte block indicated by the number variable.
-C number reads the specified file from the byte location indicated by the number variable.
-F if the input file is a regular file or if the file parameter specifies FIFO (first-in-first-out ),
The tail command will not terminate after the last specified unit of the input file is copied, but will continue
Read and copy additional units from the input file (when these units are available ). If the file parameter is not specified,
If the standard input is a pipe, the-F flag is ignored. The tail-F command can be used to monitor another process
The number of written files increases.
-K Number reads the specified file from the 1kb block location indicated by the number variable.
-M number reads the specified file from the Multi-byte character position indicated by the number variable. Use this flag to provide
Consistent results in the single-byte and double-byte character code set environment.
-N number reads the specified file from the first or last row. The position is indicated by the number variable symbol (+ or-or none)
And shift by the number of the row.
-R displays the output in reverse order from the end of the file. The default value of the-r flag is to display the entire file in reverse order.
If the file is larger than 20,480 bytes, the-r flag only displays the last 20,480 bytes. -R flag only
It is valid only when it is used together with the-n mark. Otherwise, it will be ignored.