pv是一款Liunx下的限流工具，可以使用该工具查看任务进度，传输速率，使用
pv示例
# 我的MySQL
wing@3306>select count(*) from t;
+----------+
| count(*) |
+----------+
| 25165824 |
+----------+
1 row in set (10.94 sec)
[
12K t.frm
741M t.ibd
# 此时我不使用pv工具完成该表的
[root@wing ~]#
[root@wing ~]#
# 此时我使用pv工具完成该表的备份,我们可以看到文件已经传输的大小，使用时间，传输速率，已经进度条(感觉进度条不是特别准确的样子)
[root@wing ~]# mysqldump -uroot -P3306 -h127.0.0.1 wing t | pv > dump.sql
429MiB 0:00:32 [13.1MiB/s] [ <=> ]
pv
Usage: pv [OPTION] [FILE]…Con
-p, –progress
show progress bar显示进度条(目测不是很准的样子==)(默认)
-t, –timer
show elapsed time显示任务已经进行的时长(默认)
-e, –eta
show estimated time of arrival (completion)显示剩余多长时间完成(默认，但好像并不能显示)
-r, –rate
show data transfer rate counter显示当前传输速率(默认)
-a, –average-rate
show data transfer average rate counter显示平均传输速率
-b, –bytes
show number of bytes transferred
-F, –format FORMAT
set output format to FORMAT
-n, –numeric
output percentages, not visual information显示进度百分比
-q, –quiet
do not output any transfer information at all不输出任何信息
-W, –wait
display nothing until first byte transferred
-s, –size SIZE
set estimated data size to SIZE bytes
-l, –line-mode
count lines instead of bytes
-i, –interval SEC
-w, –width WIDTH
assume ter
-H, –height HEIGHT
assume te
-N, –name NAME
prefix visual information with NAME
-f, –force
output even if standard error is not a terminal
-c, –cursor
use cursor positioning escape sequences
L, –rate-limit RATE
limit transfer to RATE bytes per second限制每秒的传输速率，RATE可为n,nK,nM,nG
-B, –buffer-size BYTES
use a buffer size of BYTES
-E, –sk
skip read errors in input
-S, –stop-at-size
stop after –size bytes have been transferred
-R, –
update settings of process PID
-P, –pidfile FILE
save process ID in FILE
-h, –help
show this help and exit
-V, –version
show version information and exit
Please report any bugs to Andrew Wood andrew.wood@ivarch.com .