Summery
ログデータなど、割りと膨大なテキストデータの最後から数えて◯行目までを表示する機能
Construction
$ tail [option] [file]
Option
-f : リアルタイム監視 ※追記されたら、表示処理をしてくれる
-n : 表示する最後から数えた行数
-q : ファイル名を表示しない
-v : ファイル名を表示する
Sample
# 末尾10行を表示する
$ tail -n 10 /var/log/apache2/error.log
# リアルタイム監視する
$ tail -f /var/log/apache2/error.log
Discription
The tail utility displays the contents of file or, by default, its standard input, to
the standard output.
The display begins at a byte, line or 512-byte block location in the input. Numbers
having a leading plus (`+') sign are relative to the beginning of the input, for exam-
ple, ``-c +2'' starts the display at the second byte of the input. Numbers having a
leading minus (`-') sign or no explicit sign are relative to the end of the input, for
example, ``-n 2'' displays the last two lines of the input. The default starting loca-
tion is ``-n 10'', or the last 10 lines of the input.
The options are as follows:
-b number
The location is number 512-byte blocks.
-c number
The location is number bytes.
-f The -f option causes tail to not stop when end of file is reached, but rather to
wait for additional data to be appended to the input. The -f option is ignored
if the standard input is a pipe, but not if it is a FIFO.
-F The -F option implies the -f option, but tail will also check to see if the file
being followed has been renamed or rotated. The file is closed and reopened
when tail detects that the filename being read from has a new inode number. The
-F option is ignored if reading from standard input rather than a file.
-n number
The location is number lines.
-q Suppresses printing of headers when multiple files are being examined.
-r The -r option causes the input to be displayed in reverse order, by line. Addi-
tionally, this option changes the meaning of the -b, -c and -n options. When
the -r option is specified, these options specify the number of bytes, lines or
512-byte blocks to display, instead of the bytes, lines or blocks from the
beginning or end of the input from which to begin the display. The default for
the -r option is to display all of the input.
If more than a single file is specified, each file is preceded by a header consisting of
the string ``==> XXX < =='' where XXX is the name of the file unless -q flag is speci-
fied.
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