Using getline into a variable from a coprocess sometimes overwrites RT

[Nick Hobson]

Hi,

I think I've found a gawk bug.  In some cases, using getline into a variable 
from a coprocess clobbers RT.  It doesn't touch $0 or NF.  I have demonstrated 
the problem in gawk 3.1.7 under Arch Linux.

The test program is:

BEGIN {RS = "u"}

RT == "u" {
    printf callpgm("xargs file -b ", "imgs/auk.png")
}

function callpgm(ext, src,  res) {
    print src |& ext
    close(ext, "to")
    print "1", $0, NF, RT
    ext |& getline res
    print "2", $0, NF, RT
    close(ext)
    return res
}

The input data is:

bug

When run as echo 'bug' | bug.awk, the expected output is:

1 b 1 u
2 b 1 u
PNG image, 500 x 600, 8-bit colormap, non-interlaced

The actual output is:

1 b 1 u
2 b 1 
PNG image, 500 x 600, 8-bit colormap, non-interlaced

The getline sets RT to the empty string.  (The actual value RT is overwritten 
with varies.  If you change the above BEGIN block to RS = "[aeiou]", RT gets 
overwritten with "i".)

Attached: bug.awk

Regards,
Nick Hobson

bug.awk
Description: Binary data