ファイルの先頭や末尾を表示させる

忘れっぽいのでメモをしておく

ログとか、「あー、ちょっとだけこのファイルの中身、確認したいな」って時にcatほど全部見たくないときにtailとかheadを使う。

tail

ファイルの末尾から10行(デフォルト)を表示させる。
オプションは
-c でバイト数を指定とか -l で行数を指定とか。

]# tail --help
Usage: tail [OPTION]... [FILE]...
Print the last 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
--retry keep trying to open a file even if it is
inaccessible when tail starts or if it becomes
inaccessible later -- useful only with -f
-c, --bytes=N output the last N bytes
-f, --follow[={name|descriptor}]
output appended data as the file grows;
-f, --follow, and --follow=descriptor are
equivalent
-F same as --follow=name --retry
-n, --lines=N output the last N lines, instead of the last 10
--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 renamed
(this is the usual case of rotated log files)
--pid=PID with -f, terminate after process ID, PID dies
-q, --quiet, --silent never output headers giving file names
-s, --sleep-interval=S with -f, sleep for approximately S seconds
(default 1.0) between iterations.
-v, --verbose always output headers giving file names
--help display this help and exit
--version output version information and exit

If the first character of N (the number of bytes or lines) is a `+',
print beginning with the Nth item from the start of each file, otherwise,
print the last N items in the file. N may have a multiplier suffix:
b 512, k 1024, m 1024*1024.

With --follow (-f), tail defaults to following the file descriptor, which
means that even if a tail'ed file is renamed, tail will continue to track
its end. This default behavior is not desirable when you really want to
track the actual name of the file, not the file descriptor (e.g., log
rotation). Use --follow=name

head

tailとは反対にファイルの先頭を10行(デフォルト)表示させる。
オプションはほぼ同じ。

# head --help
Usage: head [OPTION]... [FILE]...
Print the first 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
-c, --bytes=[-]N print the first N bytes of each file;
with the leading `-', print all but the last
N bytes of each file
-n, --lines=[-]N print the first N lines instead of the first 10;
with the leading `-', print all but the last
N lines of each file
-q, --quiet, --silent never print headers giving file names
-v, --verbose always print headers giving file names
--help display this help and exit
--version output version information and exit

N may have a multiplier suffix: b 512, k 1024, m 1024*1024.

Report bugs to .