следить за прохождением данных по каналу (monitor the progress of data through a pipe)
Имя (Name)
pv - monitor the progress of data through a pipe
Синопсис (Synopsis)
pv [OPTION] [FILE]...
pv [-h|-V]
Описание (Description)
pv shows the progress of data through a pipeline by giving
information such as time elapsed, percentage completed (with
progress bar), current throughput rate, total data transferred,
and ETA.
To use it, insert it in a pipeline between two processes, with
the appropriate options. Its standard input will be passed
through to its standard output and progress will be shown on
standard error.
pv will copy each supplied FILE in turn to standard output (-
means standard input), or if no FILEs are specified just standard
input is copied. This is the same behaviour as cat(1).
A simple example to watch how quickly a file is transferred using
nc(1):
pv file | nc -w 1 somewhere.com 3000
A similar example, transferring a file from another process and
passing the expected size to pv:
cat file | pv -s 12345 | nc -w 1 somewhere.com 3000
A more complicated example using numeric output to feed into the
dialog(1) program for a full-screen progress display:
(tar cf - . \
| pv -n -s $(du -sb . | awk '{print $1}') \
| gzip -9 > out.tgz) 2>&1 \
| dialog --gauge 'Progress' 7 70
Taking an image of a disk, skipping errors:
pv -EE /dev/sda > disk-image.img
Writing an image back to a disk:
pv disk-image.img > /dev/sda
Zeroing a disk:
pv < /dev/zero > /dev/sda
Note that if the input size cannot be calculated, and the output
is a block device, then the size of the block device will be used
and pv will automatically stop at that size as if -S had been
given.
(Linux only): Watching file descriptor 3 opened by another
process 1234:
pv -d 1234:3
(Linux only): Watching all file descriptors used by process 1234:
pv -d 1234
Параметры (Options)
pv takes many options, which are divided into display switches,
output modifiers, and general options.
DISPLAY SWITCHES
If no display switches are specified, pv behaves as if -p, -t,
-e, -r, and -b had been given (i.e. everything except average
rate is switched on). Otherwise, only those display types that
are explicitly switched on will be shown.
-p, --progress
Turn the progress bar on. If standard input is not a file
and no size was given (with the -s modifier), the progress
bar cannot indicate how close to completion the transfer
is, so it will just move left and right to indicate that
data is moving.
-t, --timer
Turn the timer on. This will display the total elapsed
time that pv has been running for.
-e, --eta
Turn the ETA timer on. This will attempt to guess, based
on previous transfer rates and the total data size, how
long it will be before completion. This option will have
no effect if the total data size cannot be determined.
-I, --fineta
Turn the ETA timer on, but display the estimated local
time of arrival instead of time left. When the estimated
time is more than 6 hours in the future, the date is shown
as well.
-r, --rate
Turn the rate counter on. This will display the current
rate of data transfer.
-a, --average-rate
Turn the average rate counter on. This will display the
average rate of data transfer so far.
-b, --bytes
Turn the total byte counter on. This will display the
total amount of data transferred so far.
-T, --buffer-percent
Turn on the transfer buffer percentage display. This will
show the percentage of the transfer buffer in use - but
see the caveat under %T in the FORMATTING section below.
-A, --last-written NUM
Show the last NUM bytes written - but see the caveat under
%nA in the FORMATTING section below.
-F, --format FORMAT
Ignore the options -p, -t, -e, -r, -a, -b, -T, and -A, and
instead use the format string FORMAT to determine the
output format. See the FORMATTING section below.
-n, --numeric
Numeric output. Instead of giving a visual indication of
progress, pv will give an integer percentage, one per
line, on standard error, suitable for piping (via
convoluted redirection) into dialog(1). Note that -f is
not required if -n is being used.
Note that if --numeric is in use, then adding --bytes will
cause the number of bytes processed so far to be output
instead of a percentage; if --line-mode is also in use,
then instead of bytes or a percentage, the number of lines
so far is output. And finally, if --timer is also in use,
then each output line is prefixed with the elapsed time so
far, as a decimal number of seconds.
-q, --quiet
No output. Useful if the -L option is being used on its
own to just limit the transfer rate of a pipe.
Модификаторы выхода (Output modifiers)
-W, --wait
Wait until the first byte has been transferred before
showing any progress information or calculating any ETAs.
Useful if the program you are piping to or from requires
extra information before it starts, eg piping data into
gpg(1) or mcrypt(1) which require a passphrase before data
can be processed.
-D, --delay-start SEC
Wait until SEC seconds have passed before showing any
progress information, for example in a script where you
only want to show a progress bar if it starts taking a
long time. Note that this can be a decimal such as 0.5.
-s SIZE, --size SIZE
Assume the total amount of data to be transferred is SIZE
bytes when calculating percentages and ETAs. The same
suffixes of "k", "m" etc can be used as with -L.
Has no effect if used with -d PID to watch all file
descriptors of a process, but will work with -d PID:FD.
-l, --line-mode
Instead of counting bytes, count lines (newline
characters). The progress bar will only move when a new
line is found, and the value passed to the -s option will
be interpreted as a line count. Note that file sizes are
not automatically calculated when this option is used, to
avoid having to read all files twice.
-0, --null
Count lines as null terminated. This option implies
--line-mode.
-i SEC, --interval SEC
Wait SEC seconds between updates. The default is to
update every second. Note that this can be a decimal such
as 0.1.
-w WIDTH, --width WIDTH
Assume the terminal is WIDTH characters wide, instead of
trying to work it out (or assuming 80 if it cannot be
guessed).
-H HEIGHT, --height HEIGHT
Assume the terminal is HEIGHT rows high, instead of trying
to work it out (or assuming 25 if it cannot be guessed).
-N NAME, --name NAME
Prefix the output information with NAME. Useful in
conjunction with -c if you have a complicated pipeline and
you want to be able to tell different parts of it apart.
-f, --force
Force output. Normally, pv will not output any visual
display if standard error is not a terminal. This option
forces it to do so.
-c, --cursor
Use cursor positioning escape sequences instead of just
using carriage returns. This is useful in conjunction
with -N (name) if you are using multiple pv invocations in
a single, long, pipeline.
DATA TRANSFER MODIFIERS
-L RATE, --rate-limit RATE
Limit the transfer to a maximum of RATE bytes per second.
A suffix of "K", "M", "G", or "T" can be added to denote
kibibytes (*1024), mebibytes, and so on.
-B BYTES, --buffer-size BYTES
Use a transfer buffer size of BYTES bytes. A suffix of
"K", "M", "G", or "T" can be added to denote kibibytes
(*1024), mebibytes, and so on. The default buffer size is
the block size of the input file's filesystem multiplied
by 32 (512KiB max), or 400KiB if the block size cannot be
determined.
-C, --no-splice
Never use splice(2), even if it would normally be
possible. The splice(2) system call is a more efficient
way of transferring data from or to a pipe than regular
read(2) and write(2), but means that the transfer buffer
may not be used. This prevents -A and -T from working, so
if you want to use -A or -T then you will need to use -C,
at the cost of a small loss in transfer efficiency. (This
option has no effect on systems where splice(2) is
unavailable).
-E, --skip-errors
Ignore read errors by attempting to skip past the
offending sections. The corresponding parts of the output
will be null bytes. At first only a few bytes will be
skipped, but if there are many errors in a row then the
skips will move up to chunks of 512. This is intended to
be similar to dd conv=sync,noerror but has not been as
thoroughly tested.
Specify -E twice to only report a read error once per
file, instead of reporting each byte range skipped.
-S, --stop-at-size
If a size was specified with -s, stop transferring data
once that many bytes have been written, instead of
continuing to the end of input.
-d PID[:FD], --watchfd PID[:FD]
Instead of transferring data, watch file descriptor FD of
process PID, and show its progress. The pv process will
exit when FD either changes to a different file, changes
read/write mode, or is closed; other data transfer
modifiers - and remote control - may not be used with this
option.
If only a PID is specified, then that process will be
watched, and all regular files and block devices it opens
will be shown with a progress bar. The pv process will
exit when process PID exits.
-R PID, --remote PID
If PID is an instance of pv that is already running, -R
PID will cause that instance to act as though it had been
given this instance's command line instead. For example,
if pv -L 123K is running with process ID 9876, then
running pv -R 9876 -L 321K will cause it to start using a
rate limit of 321KiB instead of 123KiB. Note that some
options cannot be changed while running, such as -c, -l,
-f, -D, -E, and -S.
Общие настройки (General options)
-P FILE, --pidfile FILE
Save the process ID of pv in FILE. The file will be
truncated if it already exists, and will be removed when
pv exits. While pv is running, it will contain a single
number - the process ID of pv - followed by a newline.
-h, --help
Print a usage message on standard output and exit
successfully.
-V, --version
Print version information on standard output and exit
successfully.
FORMATTING
If the -F option is given, then the output format is determined
by the given format string. Within that string, the following
sequences can be used:
%p Progress bar. Expands to fill the remaining space. Should
only be specified once. Equivalent to -p.
%t Elapsed time. Equivalent to -t.
%e ETA as time remaining. Equivalent to -e.
%I ETA as local time of completion. Equivalent to -I.
%r Current data transfer rate. Equivalent to -r.
%a Average data transfer rate. Equivalent to -a.
%b Bytes transferred so far (or lines if -l was specified).
Equivalent to -b.
%T Percentage of the transfer buffer in use. Equivalent to
-T. Shows "{----}" if the transfer is being done with
splice(2), since splicing to or from pipes does not use
the buffer.
%nA Show the last n bytes written (e.g. %16A for the last 16
bytes). Shows only dots if the transfer is being done
with splice(2), since splicing to or from pipes does not
use the buffer.
%N Name prefix given by -N. Padded to 9 characters with
spaces, and suffixed with :.
%% A single %.
The format string equivalent of turning on all display switches
is `%N %b %T %t %r %a %p %e'.
COMMON SWITCHES
Some suggested common switch combinations:
pv -ptebar
Show a progress bar, elapsed time, estimated completion
time, byte counter, average rate, and current rate.
pv -betlap
Show a progress bar, elapsed time, estimated completion
time, line counter, and average rate, counting lines
instead of bytes.
pv -t Show only the elapsed time - useful as a simple timer,
e.g. sleep 10m | pv -t.
pv -pterb
The default behaviour: progress bar, elapsed time,
estimated completion time, current rate, and byte counter.
Статус выхода (Exit)
An exit status of 1 indicates a problem with the -R or -P
options.
Any other exit status is a bitmask of the following:
2 One or more files could not be accessed, stat(2)ed, or
opened.
4 An input file was the same as the output file.
8 Internal error with closing a file or moving to the next
file.
16 There was an error while transferring data from one or
more input files.
32 A signal was caught that caused an early exit.
64 Memory allocation failed.
A zero exit status indicates no problems.
