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# NAME
pv - monitor the progress of data through a pipe
# SYNOPSIS
**pv** \[*OPTION*\] \[*FILE*\]\...\
**pv** \[*-h*\|*-V*\]
# 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 *FILE*s 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**
# 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. 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. The countdown is prefixed with \"ETA\". 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 at which
the transfer will finish, instead of the amount of time remaining.
When the estimated time is more than 6 hours in the future, the date
is shown as well. The time is prefixed with \"FIN\" for finish time.
As with **\--eta**, this option will have no effect if the total
data size cannot be determined.
**-r, \--rate**
: Turn the rate counter on. This will display the current rate of data
transfer. The rate is shown in square brackets \[\].
**-a, \--average-rate**
: Turn the average rate counter on. This will display the current
average rate of data transfer (default: last 30s, see **-m**). The
average rate is shown in brackets ().
**-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**. The
transfer buffer percentage is shown in curly brackets {}.
**-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.
**-v, \--stats**
: At the end of the transfer, write an additional line showing the
transfer rate minimum, maximum, mean, and standard deviation. The
values are always in bytes per second (or bits, with **-8**).
**-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.
: 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. If **\--rate** is
added, then the transfer rate is also output (if **\--bytes** is in
use as well, the rate comes after the byte/line count). If
**\--timer** is also added, 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 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.
# DATA TRANSFER MODIFIERS
**-o FILE, \--output FILE**
: Write data to *FILE* rather than standard output. If the file
already exists, it will be truncated.
**-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**.
# GENERAL OPTIONS
**-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.
# 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 at which the transfer will finish. 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 %I\'**.
# 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.
On MacOS, it may be useful to specify **-B 1024** in a pipeline, as this
may improve performance.
# 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.
# ENVIRONMENT
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.
# AUTHOR
Written by Andrew Wood, with patches submitted by various other people.
Please see the package\'s ACKNOWLEDGEMENTS file for a complete list of
contributors.
# KNOWN PROBLEMS
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.
# REPORTING BUGS
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\>
# SEE ALSO
**cat**(1), **dialog**(1), **splice**(2), **open**(2) (for **O_DIRECT**)
# COPYRIGHT
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.
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