pv

Monitor the progress of data through a pipe.

Syntax
      pv [OPTION] [FILE]...

      pv [-h|-V] 

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 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 thatdata 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. 
   -r, --rate
       Turn the rate counter on. This will display the current rate of data transfer. 
   -b, --bytes
       Turn the total byte counter on. This will display the total amount of data transferred so far. 
   -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. 
   -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. 
   -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. 
   -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. 
   -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. 
   -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, and -f.

General Options

   -h, --help
       Print a usage message on standard output and exit successfully. 
   -V, --version
       Print version information on standard output and exit successfully.

pv allows a user to see 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

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.

“Put that in your pipe and smoke it” ~ Proverb

Related :

cat - Concatenate and print (display) the content of files


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