PV(1) User Manuals PV(1)NAMEpv - monitor the progress of data through a pipe
SYNOPSISpv [OPTION] [FILE]...
pv [-h|-V]
DESCRIPTIONpv 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 dia‐
log(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
OPTIONSpv 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 can‐
not 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.
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 kilobytes
(*1024), megabytes, 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 kilobytes (*1024),
megabytes, and so on. The default buffer size is the block size
of the input file's filesystem multiplied by 32 (512kb max), or
400kb 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 sec‐
tions. 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 321k instead of
123k. Note that some options cannot be changed while running,
such as -c, -l, -f, -D, -E, and -S.
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 success‐
fully.
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). Equiv‐
alent 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 buf‐
fer.
%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'.
EXIT STATUS
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.
AUTHOR
Written by Andrew Wood, with patches submitted by various other people.
Please see the package README for a complete list of contributors.
KNOWN PROBLEMS
The following problems are known to exist in pv:
* The -c option does not work properly on Cygwin without cygserver
running, if started near the bottom of the screen (IPC is needed
to handle the terminal scrolling). To fix this, start cygserver
before using pv-c.
* The -R option is not available on Cygwin without cygserver run‐
ning (SYSV IPC is needed). To fix this, start cygserver before
running the instance of pv you want, at runtime, to change the
parameters of.
If you find any other problems, please report them.
REPORTING BUGS
Report bugs in pv to pv@ivarch.com or use the contact form linked from
the pv home page: <http://www.ivarch.com/programs/pv.shtml>
SEE ALSOcat(1), dialog(1), splice(2)LICENSE
This is free software, distributed under the ARTISTIC 2.0 license.
Linux March 2015 PV(1)
