tail

Copy the last part of files (POSIX)

Syntax:

tail [-number] [-fl] [-c number | -n number] [file]...

Options:

- number
Deprecated; use -n number instead.
-c number
Copy the given number of bytes; see below.
-f
If the input file is a regular file (i.e. not a tty or FIFO), don't terminate after the last line of the input file has been copied, but enter a continuous loop. The tail utility then sleeps for approximately one second, then attempts to read and copy further bytes from the input file.
-l
("el") Measure the quantity of output in lines; this is the default unit of measure. Deprecated; use -n number instead.
-n number
Copy the given number of lines; see below.
file
The pathname of an input file. If you don't specify a file, the standard input is used.

Description:

The tail utility copies its input files to the standard output, beginning at the point in the files indicated by the -c or -n option. For both options, the number argument is a decimal integer whose sign specifies the location in the file to begin copying:

If the sign is:  Then copying starts relative to the:
+ Beginning of the file
- End of the file
Omitted End of the file

If you don't specify a -c or -n option, the default is -n 10 (i.e. the last ten lines of the file).

If you use both -c and the deprecated -l option, the order of the options is important. If you specify:

tail -l -c 5 my_file

then tail copies 5 bytes. If you specify:

tail -c 5 -l my_file

it copies 5 lines.

When tail is applied to a nonseekable file (e.g. a tty), tail must maintain an internal buffer. This buffer is large enough to hold at least 10 lines of characters.

Examples:

You can use the -f option to monitor the growth of a file that is being written by a process. For example, the command:

tail -f fred

prints the last ten lines of the file fred, followed by any lines that are appended to fred between the time tail is initiated and terminated. As another example, the command:

tail -f -c 15 fred

prints the last 15 bytes of the file fred, followed by any lines that are appended to fred between the time tail is initiated and terminated.

Exit status:

0
Successful completion.
>0
An error occurred.

Last modified: 2014-05-14



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