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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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PV(1) User Manuals PV(1)
pv - monitor the progress of data through a pipe
pv [OPTION] [FILE]...
pv [-h|-V]
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/your/disk/device > disk-image.img
Writing an image back to a disk:
pv disk-image.img > /dev/your/disk/device
Zeroing a disk:
pv < /dev/zero > /dev/your/disk/device
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
pv takes many options, which are divided into display switches,
output modifiers, and general options.
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 any inputs are not files, or
are unreadable, and no size was explicitly 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 current 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
current average rate of data transfer (default: last 30s,
see -m).
-b, --bytes
Turn the total byte counter on. This will display the
total amount of data transferred so far.
-8, --bits
Display the total bits instead of the total bytes. The
output suffix will be "b" instead of "B".
-k, --si
Display and interpret suffixes as multiples of 1000 rather
than the default of 1024. Note that this only takes
effect on options after this one, so for consistency,
specify this option first.
-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.
Implies -C.
-A NUM, --last-written NUM
Show the last NUM bytes written - but see the caveat under
%nA in the FORMATTING section below. Implies -C.
-F FORMAT, --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 as
well as --bytes and --numeric, then instead of bytes or a
percentage, the number of lines so far is output. And
finally, if --timer is added to --numeric, 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.
-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 SEC, --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.
If SIZE starts with @, the size of file whose name follows
the @ will be used.
Note that --size 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.
If this option is used without -s, the "total size" (in
this case, total line count) is calculated by reading
through all input files once before transfer starts. If
any inputs are pipes or non-regular files, or are
unreadable, the total size will not be calculated.
-0, --null
Count lines as terminated with a zero byte instead of with
a newline. 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.
-m SEC, --average-rate-window SEC
Compute current average rate over a SEC seconds window for
average rate and ETA calculations (default 30 seconds).
-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). If this option is used, the output width will
not be adjusted if the width of the terminal changes while
the transfer is running.
-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).
If this option is used, the output height will not be
adjusted if the height of the terminal changes while the
transfer is running.
-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.
-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. If --si was also
passed, suffixes will denote kilobytes (*1000), megabytes,
etc. Note the caveat about the positioning of --si .
-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. This can be useful on platforms like MacOS
which perform better in pipelines with specific buffer
sizes such as 1024. Implies -C.
-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,
cannot work with -X, and makes -B redundant, so using -A,
-T, -X, or -B automatically switches on -C. Switching on
-C results in a small loss of 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.
-Z BYTES, --error-skip-block BYTES
When ignoring read errors with -E, instead of trying to
adaptively skip by reading small amounts and skipping
progressively larger sections until a read succeeds, move
to the next file block of BYTES bytes as soon as an error
occurs. There may still be some shorter skips where the
block being skipped coincides with the end of the transfer
buffer.
This option can only be used with -E and is intended for
use when reading from a block device, such as -E -Z 4K to
skip in 4 kibibyte blocks. This will speed up reads from
faulty media, at the expense of potentially losing more
data.
-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.
-Y, --sync
After every write operation, synchronise the buffer caches
to disk - see fdatasync(2). This has no effect when the
output is a pipe. Using -Y may improve the accuracy of
the progress bar when writing to a slow disk.
-K, --direct-io
Set the O_DIRECT flag on all inputs and outputs, if it is
available. This will minimise the effect of caches, at
the cost of performance. Due to memory alignment
requirements, it also may cause read or write failures
with an error of "Invalid argument", especially if reading
and writing files across a variety of filesystems in a
single pv call. Use this option with caution.
-X, --discard
Instead of transferring input data to standard output,
discard it. This is equivalent to redirecting standard
output to /dev/null, except that write(2) is never called.
Implies -C.
-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.
-P FILE, --pidfile FILE
Save the process ID of pv in FILE. The file will be
replaced 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.
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. If --bits was specified, %b shows the
bits transferred so far, not bytes.
%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'.
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.
On MacOS, it may be useful to specify -B 1024 in a pipeline, as
this may improve performance.
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.
The following environment variables may affect pv:
HOME The current user's home directory. This may be used by
the remote control mechanism (the --remote option) to
exchange messages between pv instances: if the
/run/user/UID/ directory does not exist (where UID is the
current user ID), then $HOME/.pv/ will be used instead.
TMPDIR, TMP
The directory to create per-tty lock files for the
terminal when using the --cursor option. If TMPDIR is set
to a non-empty value, it is the directory under which lock
files are created. Otherwise, if TMP is set, then it is
used; and if neither are set, then /tmp is used.
Written by Andrew Wood, with patches submitted by various other
people. Please see the package's ACKNOWLEDGEMENTS file for a
complete list of contributors.
The following problems are known to exist in pv:
• In some versions of bash(1) and zsh(1), the construct <(pv
filename) will not output any progress to the terminal when
run from an interactive shell, due to the subprocess being run
in a separate process group from the one that owns the
terminal. In these cases, use --force.
• 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 requires that either /run/user/<uid>/ or $HOME/
can be written to, for inter-process communication.
If you find any other problems, please report them.
Please report any bugs to pv@ivarch.com.
Alternatively, use the issue tracker linked from the pv home
page: <https://www.ivarch.com/programs/pv.shtml>
cat(1), dialog(1), splice(2), open(2) (for O_DIRECT)
Copyright © 2002-2008, 2010, 2012-2015, 2017, 2021, 2023-2024
Andrew Wood.
License GPLv3+: GNU GPL version 3 or later
<https://www.gnu.org/licenses/gpl-3.0.html>.
This is free software: you are free to change and redistribute
it. There is NO WARRANTY, to the extent permitted by law.
This page is part of the pv (Pipe Viewer) project. Information
about the project can be found at
⟨http://www.ivarch.com/programs/pv.shtml⟩. If you have a bug
report for this manual page, see
⟨http://www.ivarch.com/programs/pv.shtml⟩. This page was
obtained from the tarball pv-1.8.9.tar.gz fetched from
⟨http://www.ivarch.com/programs/pv.shtml⟩ on 2024-06-14. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
Linux April 2024 PV(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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