gawk - printf discards field-width when space modifier used

[David C. Rankin]

Version:

GNU Awk 5.1.1, API: 3.1 (GNU MPFR 4.1.0-p13, GNU MP 6.2.1)
Copyright (C) 1989, 1991-2021 Free Software Foundation.

Problem:

When using printf with both the space modifier and field-width modifier for
integer conversions with %d, gawk discards the field-width.

Specific code producing the problem:

  printf j ? " % 4d%s" : "% 4d%s", rv, (j<cols-1) ? "" : ORS

This is from a simple shell script calling gawk to generate (rows x cols)
random values between two numbers. The full script used was:

#!/bin/sh

rows="${1:-10}"
cols="${2:-10}"
min="${3:-0}"
max="${4:-10000}"

awk -v rows="$rows" -v cols="$cols" -v min="$min" -v max="$max" 'BEGIN {
  minval = max
  maxval = min
  srand(systime())
  for (i=0; i<rows; i++)
    for (j=0; j<cols; j++) {
      rv = rand() * (max - min) + min
      if (rv < minval)
        minval = rv
      if (rv > maxval)
        maxval = rv
      printf j ? " % 4d%s" : "% 4d%s", rv, (j<cols-1) ? "" : ORS > "file.txt"
    }
  printf "min: %d\nmax: %d\n", minval, maxval
}'

Run with the default values to produce a 10x10 set of random numbers in
file.txt, the result is:

 1367  7362  2586  9128  467  9470  8295  2085  5238  1928
 5658  2652  5527  7186  6550  1673  6640  1593  1502  5424
 626  675  9768  2499  9257  2432   60  6278  7153  7959
 7805  7831  6708  7110  6285  2011  1043  7112  7581  7745
 2448  3545  8473  202  8572  1035  2253  7257  4355  1096
 1682  4781  2344  5567  9050  5512  5837  4602  9141  6737
 9568  2973  5336  7953  7887  764  4140  7339  1920  6316
 3226  9611  7985  4853  3722  5866  8133  3795  3079  6658
 5025  3298  4411  1328  1696  4740  1159  7499  1810  7463
 9938  2950  9804  1171  9052  7699  6753  2680  3311  9405

The space is added by the space modifier, but the field-width is discarded.

Removing the space modifier, the field-width is respected, e.g. the output 
being:

2938 3689 2227 1662 7370 6126 4443 1828 3618 9347
1961 8360 2819 4660 4883 7350 6409 3724 1515 4174
7810 3554 1055 1063 9286 3066   72 1891 3108 9379
1907 8978 6766 8849 7350 2830 2795 9534 8067 1310
3587 5381 9685  180 5213 9720 8209 2341 4015 8178
9819 1507 3783  463 7155 2293 5173 8983 1941 3586
8470 3450 9740 1911 4338 3591 5764 3035 7204 5496
7598 4130 9789 3732 9274 7391 5039 9027 9680 1729
6523 7546 7890  786 9406 5975 7172 6966 8772 6618
5932 8723   24 1334 1957 1208 1215 8047 5697 3722

This behavior is contrary to man 3 printf and
https://www.gnu.org/software/gawk/manual/html_node/Format-Modifiers.html


-- 
David C. Rankin, J.D.,P.E.