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005-the-tail-command.md

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The tail command

The tail command prints the last ten lines of a file.

Example:

tail filename.txt

Syntax:

tail [OPTION] [FILENAME]

Get a specific number of lines with tail:

Use the -n option with a number(should be an integer) of lines to display.

Example:

tail -n 10 foo.txt

This command will display the last ten lines of the file foo.txt.

Refresh the output on any new entry in a file

It is possible to let tail output any new line added to the file you are looking into. So, if a new line is written to the file, it will immediately be shown in your output. This can be done using the --follow or -f option. This is especially useful for monitoring log files.

Example:

tail -f foo.txt

Syntax:

tail -n <number> foo.txt

Additional Flags and their Functionalities

Short Flag Long Flag Description
-c --bytes=[+]NUM Output the last NUM bytes;
or use -c +NUM to
output starting with byte NUM of each file
-f --follow[={name|descriptor}] Output appended data as the file grows;
an absent option argument means 'descriptor'
-F Same as --follow=name --retry
-n --lines=[+]NUM Output the last NUM lines, instead of the last 10;
or use -n +NUM to output starting with line NUM
--max-unchanged-stats=N with --follow=name, reopen a FILE which has not
changed size after N (default 5) iterations
to see if it has been unlinked or rename
(this is the usual case of rotated log files);
with inotify, this option is rarely useful
--pid=PID with -f, terminate after process ID, PID dies
-q --quiet, --silent Never output headers giving file names
`` --retry keep trying to open a file if it is inaccessible
-s --sleep-interval=N With -f, sleep for approximately N seconds
(default 1.0) between iterations;
with inotify and --pid=P, check process P at
least once every N seconds
-v --verbose Always output headers giving file names
-z --zero-terminated Line delimiter is NUL, not newline
--help Display this help and exit
--version Output version information and exit