先日、Raspberry Pi で温度を測定するプログラムを書いたので温度をモニタリングしながらファイルに保存していこうと思ったら画面に何も出てこなかった。すっかり忘れてたけどバッファがあるんだった。
$ python2 temp.py | tee temp.csv
昔は grep --line-buffered みたいなの使ってた気がするけど、他にも無いのかと調べてみたらコマンドのバッファを変更できる stdbuf っていうちゃんとあった。
$ man -s 1 -k buffer dmesg (1) - print or control the kernel ring buffer stdbuf (1) - Run COMMAND, with modified buffering operations for its standard streams.
$ stdbuf --help
Usage: stdbuf OPTION... COMMAND
Run COMMAND, with modified buffering operations for its standard streams.
Mandatory arguments to long options are mandatory for short options too.
-i, --input=MODE adjust standard input stream buffering
-o, --output=MODE adjust standard output stream buffering
-e, --error=MODE adjust standard error stream buffering
--help display this help and exit
--version output version information and exit
If MODE is 'L' the corresponding stream will be line buffered.
This option is invalid with standard input.
If MODE is '0' the corresponding stream will be unbuffered.
Otherwise MODE is a number which may be followed by one of the following:
KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.
In this case the corresponding stream will be fully buffered with the buffer
size set to MODE bytes.
NOTE: If COMMAND adjusts the buffering of its standard streams ('tee' does
for example) then that will override corresponding changes by 'stdbuf'.
Also some filters (like 'dd' and 'cat' etc.) don't use streams for I/O,
and are thus unaffected by 'stdbuf' settings.
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Report stdbuf translation bugs to <http://translationproject.org/team/>
Full documentation at: <http://www.gnu.org/software/coreutils/stdbuf>
or available locally via: info '(coreutils) stdbuf invocation'
すっきり(´ー｀)
$ stdbuf -i0 -o0 -e0 python2 temp.py | tee temp.csv
