From Newsgroup: comp.unix.shell

I have a loop like:

exec 3< somefile
while read -ru3 fn; do
ffmpeg -i "$fn" ... "OutDir/$fn"
done

Shellcheck flags both the "read" and the "ffmpeg", with messages to the
effect that ffmpeg might swallow up stdin - not realizing that the -u3
means the "read" is not reading from stdin.

It recommends using the -nostdin option on ffmpeg, which is weird. It is
weird that it doesn't understand what -u3 means (which, I get, is bash-specific, but shellcheck is supposed to know about bash-specific
things), yet it *does* know about an obscure option of an obscure program called "ffmpeg".

Odd...

Anyway and FWIW, I ended up adding -nostdin, which seems reasonable based
on my reading of the "ffmpeg" man page, and does shut up both shellcheck messages.
--
b w r w g y b r y b
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From Newsgroup: comp.unix.shell

On 2025-03-05, Kenny McCormack <gazelle@shell.xmission.com> wrote:

I have a loop like:

exec 3< somefile
while read -ru3 fn; do
ffmpeg -i "$fn" ... "OutDir/$fn"
done

Shellcheck flags both the "read" and the "ffmpeg", with messages to the effect that ffmpeg might swallow up stdin - not realizing that the -u3
means the "read" is not reading from stdin.

Maybe the shellcheck code does know about -u, but simply doesn't
recognize it when it is clumped like that, together with another
option and its own argument.
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Mastodon: @Kazinator@mstdn.ca
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From Newsgroup: comp.unix.shell

On 05.03.2025 19:50, Kaz Kylheku wrote:

On 2025-03-05, Kenny McCormack <gazelle@shell.xmission.com> wrote:

I have a loop like:

exec 3< somefile
while read -ru3 fn; do
ffmpeg -i "$fn" ... "OutDir/$fn"
done

Shellcheck flags both the "read" and the "ffmpeg", with messages to the
effect that ffmpeg might swallow up stdin - not realizing that the -u3
means the "read" is not reading from stdin.

Maybe the shellcheck code does know about -u, but simply doesn't
recognize it when it is clumped like that, together with another
option and its own argument.

This is actually what I had just tried out of curiosity (with that
tool that I never used); the result is the same for 'read -r -u3'.

Janis

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From Newsgroup: comp.unix.shell

In article <20250305104105.793@kylheku.com>,
Kaz Kylheku <643-408-1753@kylheku.com> wrote:

On 2025-03-05, Kenny McCormack <gazelle@shell.xmission.com> wrote:

I have a loop like:

exec 3< somefile
while read -ru3 fn; do
ffmpeg -i "$fn" ... "OutDir/$fn"
done

Shellcheck flags both the "read" and the "ffmpeg", with messages to the
effect that ffmpeg might swallow up stdin - not realizing that the -u3
means the "read" is not reading from stdin.

Maybe the shellcheck code does know about -u, but simply doesn't
recognize it when it is clumped like that, together with another
option and its own argument.

No, it's the same with just -u3. In fact, the original code (that I ran through shellcheck) had just -u3. I added the 'r' later on.

I suppose I could try: -u 3
but that's not really the point.
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From Newsgroup: comp.unix.shell

In article <20250305104105.793@kylheku.com>,
Kaz Kylheku <643-408-1753@kylheku.com> wrote:

On 2025-03-05, Kenny McCormack <gazelle@shell.xmission.com> wrote:

I have a loop like:

exec 3< somefile
while read -ru3 fn; do
ffmpeg -i "$fn" ... "OutDir/$fn"
done

Shellcheck flags both the "read" and the "ffmpeg", with messages to the
effect that ffmpeg might swallow up stdin - not realizing that the -u3
means the "read" is not reading from stdin.

Maybe the shellcheck code does know about -u, but simply doesn't
recognize it when it is clumped like that, together with another
option and its own argument.

No, it's the same with just -u3. In fact, the original code (that I ran through shellcheck) had just -u3. I added the 'r' later on.

I suppose I could try: -u 3
but that's not really the point.
--
The scent of awk programmers is a lot more attractive to women than
the scent of perl programmers.

(Mike Brennan, quoted in the "GAWK" manual)
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