pad (rpad, lpad)

Command-line utility to pad text or numbers easily. This is installed as 3 separate commands: pad, lpad, and rpad. It reads a list of words from stdin and pads them with the padding specified (default 0) on left or right.

With no arguments, it will pad to the width of the longest word. However, this requires that the entire input file be read into memory so it can be processed. To handle files more efficiently, if width is specified the input will be processed line-by-line, allowing for arbitrarily large files to be processed (not yet implemented).

Usage

The help output on the command line:

Usage: pad|lpad|rpad [ <width> [ <pad-str> ] ] [options] [tokens] [ < input ]
Options:
  -l, --left  [ <width> [ <pad-str> ] ]  Pad the left side
  -r, --right [ <width> [ <pad-str> ] ]  Pad the right side
  -h, --help                             Display this help message

Expanded usage:

pad [ --left <count> <character> ] [ --right <count> <character> ] < <file>
pad [ --left <count> <character> ] [ --right <count> <character> ] <word> [ <word> ... ]

lpad [ <count> <character> ] [ --right <count> <character> ] < <file>
lpad [ <count> <character> ] [ --right <count> <character> ] <word> [ <word> ... ]

rpad [ <count> <character> ] [ --left <count> <character> ] < <file>
rpad [ <count> <character> ] [ --left <count> <character> ] <word> [ word ...]

Examples

Pad a list of words with zeros from the left to the width of the widest word (default case):

$ lpad < words.txt
$ lpad 0 0 < words.txt
$ pad --left 0 0 < words.txt
$ pad --left < words.txt
$ pad < words.txt
$ lpad these are a few words to pad
$ pad these are a few words to pad

Note that in most cases pad and lpad are functiaonlly equivalent. However, when specifying a width and token explicitly, pad will not assume that the first two characters are arguments, while lpad will do so. This leads to differences, as below:

$ pad 10 x these are a few words to pad
00010
0000x
these
00are
0000a
00few
words
000to
00pad

$ lpad 10 x these are a few words to pad
xxxxxthese
xxxxxxxare
xxxxxxxxxa
xxxxxxxfew
xxxxxwords
xxxxxxxxto
xxxxxxxpad

# and for completeness
$ rpad 10 x these are a few words to pad
thesexxxxx
arexxxxxxx
axxxxxxxxx
fewxxxxxxx
wordsxxxxx
toxxxxxxxx
padxxxxxxx

Multibyte characters are supported, but font widths mean that this doesn't appear correct visually, at least on my screen. There may be a fixed width unicode font where this outputs strictly in columns, though I expect the latin characters would seem quite spread in that case.

At the moment, multiple characters is not. Or more precisely, it does something, but it's probably not what you want. Fixing this is planned.

$ lpad 10 ウ these are a few words to pad
ウウウウウthese
ウウウウウウウare
ウウウウウウウウウa
ウウウウウウウfew
ウウウウウwords
ウウウウウウウウto
ウウウウウウウpad

$ lpad 10 abc these are a few words to pad
abcabcabcabcabcthese
abcabcabcabcabcabcabcare
abcabcabcabcabcabcabcabcabca
abcabcabcabcabcabcabcfew
abcabcabcabcabcwords
abcabcabcabcabcabcabcabcto
abcabcabcabcabcabcabcpad

Installing

At the moment, this is only distributed as source from here. I'll work on packaging it for varaious distributions: homebrew, .deb, .rpm, .apk, etc.

For now, to install, clone the repository and build it. You'll need rust and cargo installed, which you can get from rustup or your own preferred package manager. Assuming you have both installed and in your path, you can install with the following commands:

$ git clone https://github.com/puckdoug/pad.git
$ cd pad
$ make intsall

This will place the pad binary in your cargo bin directory (typically ${HOME}/.cargo/bin). A full install will link pad to lpad and rpad. Cargo doesn't support doing this and can't clean up afterwards if you do it manually.

The target would be to deploy wiht the appropriate package manager for the relevant platform.

Todo

• Implement line-by-line processing for arbitrary file sizes
• Implement multi-character padding
• Homebrew packaging for MacOS
• .deb packaging for Debian-based systems
• .rpm packaging for RedHat-based systems
• .apk packaging for Alpine-based systems
• .tgz for Slackware-based systems
• FreeBSD, NetBSD, OpenBSD Ports (or packages)
• .exe packaging for Windows