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Correction to Markdown manual link.

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Andrew Wood
2023-08-28 10:07:09 +01:00
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README.md
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-------------
A manual page is included in this distribution ("`man pv`"). Before
installation, it is in "[doc/pv.1.md](./doc/pv.1)".
installation, it is in "[doc/pv.1](./doc/pv.1.md)".
Changes are listed in "[doc/NEWS.md](./doc/NEWS.md)". The to-do list is "[doc/TODO.md](./doc/TODO.md)".
doc/pv.1.md
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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 (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 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
\--average-rate-window).
**-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\".
**-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, \--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**
: 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.
# 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**.
: 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.
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.
**-m SEC, \--average-rate-window SEC**
: Compute current average rate over a **SEC** seconds window for
average rate and ETA calculations (default 30s).
**-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. 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, and makes **-B** redundant, so using
**-A**, **-T**, 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.
**-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.
**-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 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\'**.
# 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.
# 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**.
```{=html}
<!-- -->
```
**\***
: 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**.
```{=html}
<!-- -->
```
**\***
: The **-R** option is not available on Cygwin without **cygserver**
running (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 ALSO
**cat**(1), **dialog**(1), **splice**(2), **open**(2) (for *O_DIRECT*)
# LICENSE
This is free software, distributed under the ARTISTIC 2.0 license.