How to zero pad a number

[Silicon_Pudding]

Hi,

I was wondering if there was a command to zero pad a number on the left side?

Thanks

[eraker]

I'm not sure I fully understand your question. Did you want to do this within a text file? If you do, you could probably use sed to do something like that.

Depending on the constraints involved, something like this:

sed -e 's/^\([0-9]\)/0\1/g' samplefile

Will turn this:

893756982736
8972348596298762
09689273456982756
817984718942
1872412587165
n 32956928356
  9u  98u6
u8459218204
009325661361
.103659161

Into this:

0893756982736
08972348596298762
009689273456982756
0817984718942
01872412587165
n 32956928356
  9u  98u6
u8459218204
0009325661361
.103659161

This may not be exactly what you want, however.

[Silicon_Pudding]

I mean like

345
44
5435345
434

into

0000345
0000044
5435345
0000434

Is there some library that I could use for reference?

[tech_man]

^^^ Those zeros should be ignored shouldn't they?

[Silicon_Pudding]

I don't want them to be ignored. That's the purpose of zero padding.

Does anyone have any suggestions?

Thanks

[Javasnob]

Since I use Perl for just about everything, here's my solution in Perl:

my $num_cols; # Is this fixed, or does it depend on the longest number?

while(<>) {
    chomp;
    print '0' x ($num_cols - length);
    print;
    print "\n";
}

Note that this code reads from standard input/files provided as arguments and spits out the result to standard output.

[the_unforgiven]

You could simply use printf() (in both C and perl) for printing the output with leading zeroes.
For example,

printf("%06d", num)

will print the number with leading zeroes and field width of 6 (min - if the no. has less digits than this width, it will be zero prepended).

HTH

[Cabhan]

Gah! I thought there was a way to use printf, and there we go!

So the easiest way I can think of to do this would be:

#!/usr/bin/perl

use strict;

chomp(my @lines = <>);

my $longest_length;

for $line (@lines)
{
    $longest_length = length($line) if length($line) > $longest_length;
}

for $line (@lines)
{
    printf('%0' . $longest_length - length($line) . "d\n", $line);
}

This also reads from stdin (unless you provide files on the command line) and prints to stdout.

[Silicon_Pudding]

woops... I forgot to mention that I am doing this is shell script

It's supposed to be based on the length of the largest one (not fixed), but I can easily determine that already.

[drl]

Hi.

Almost the same ... cheers, drl

SYNOPSIS
printf FORMAT [ARGUMENT]...
printf OPTION

DESCRIPTION
NOTE: your shell may have its own version of printf which will
supercede the version described here. Please refer to your shell's doc-
umentation for details about the options it supports.

Print ARGUMENT(s) according to FORMAT.
-- excerpt from man -S1 printf