Fix `warning: command substitution: ignored null byte in input`

[HuijingHei]

This is to remove safe warning when running google_nvme_id:

]# bash /usr/lib/udev/google_nvme_id -d /dev/nvme0n1
/usr/lib/udev/google_nvme_id: line 65: warning: command substitution: ignored null byte in input
ID_SERIAL_SHORT=persistent-disk-0
ID_SERIAL=Google_PersistentDisk_persistent-disk-0

]# nvme_json="$(/usr/sbin/nvme id-ns -b /dev/nvme0n1 | cut -b 384-)"
-bash: warning: command substitution: ignored null byte in input
]# nvme_json="$(/usr/sbin/nvme id-ns -b /dev/nvme0n1 | cut -b 384- | tr -d '\0')"
<no warning>

Refer to https://bugzilla.redhat.com/show_bug.cgi?id=1473642

[google-oss-prow[bot]]

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[google-oss-prow[bot]]

Hi @HuijingHei. Thanks for your PR.

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[HuijingHei]

/holdon

The warning is harmless and I do not want it to delay the merge process of https://github.com/GoogleCloudPlatform/guest-configs/pull/49, but will rebase https://github.com/GoogleCloudPlatform/guest-configs/pull/49 when it is merged.

[HuijingHei]

Do more testing:

]# nvme_json="$(/usr/sbin/nvme id-ns -b /dev/nvme0n1 | cut -b 384- | tr -d '\0')"

]# echo $nvme_json
{"device_name":"persistent-disk-0","disk_type":"PERSISTENT"}
]# device_name="$(echo "$nvme_json" | grep device_name | sed -e 's/.*"device_name":[  \t]*"\([a-zA-Z0-9_-]\+\)".*/\1/')"
]# echo $device_name
persistent-disk-0

[vorakl]

@HuijingHei , as you mentioned, this warning message is harmless. It doesn't affect a status code (which is still 0 when other conditions are fine). More over, there was this warning message a long time before.

From the other perspective, having one more external tool in a pipeline brings more challenges to support it existence in every distribution we officially support.

I don't see any reason for removing the warning at the moment, and especially, by introducing one more additional tool. It could be removed, for example, using only Bash code with no external tools, like this: read nvme_json < <(/usr/sbin/nvme id-ns -b /dev/nvme0n1 | cut -b 384-)

There is a code conflict anyway, I'll put on hold, until new circumstances come up.

[vorakl]

/hold

[HuijingHei]

@vorakl thanks for your detail info, I am OK to keep as it is. Feel free to close this.