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I have a command that runs forever and periodically output stuff until it gets killed by something else (similar to tail -f), and I want to make it so that whenever there's new output another command gets executed.

Caveats:

• I can't use Bash


• That command obviously isn't tail, it just behaves in a similar manner


• That command's output doesn't always come in lines, and I do not intend to execute that other command for each line of the output


• Polling is not an acceptable solution

shell-script shell

share|improve this question

asked 50 mins ago

Hwi417Hwi417

262

add a comment | 

0

I have a command that runs forever and periodically output stuff until it gets killed by something else (similar to tail -f), and I want to make it so that whenever there's new output another command gets executed.

Caveats:

• I can't use Bash


• That command obviously isn't tail, it just behaves in a similar manner


• That command's output doesn't always come in lines, and I do not intend to execute that other command for each line of the output


• Polling is not an acceptable solution

shell-script shell

share|improve this question

asked 50 mins ago

Hwi417Hwi417

262

add a comment | 

I have a command that runs forever and periodically output stuff until it gets killed by something else (similar to tail -f), and I want to make it so that whenever there's new output another command gets executed.

Caveats:

• I can't use Bash


• That command obviously isn't tail, it just behaves in a similar manner


• That command's output doesn't always come in lines, and I do not intend to execute that other command for each line of the output


• Polling is not an acceptable solution

shell-script shell

share|improve this question

asked 50 mins ago

Hwi417Hwi417

262

share|improve this question

asked 50 mins ago

Hwi417Hwi417

262

share|improve this question

asked 50 mins ago

Hwi417Hwi417

262

asked 50 mins ago

Hwi417Hwi417

262

asked 50 mins ago

Hwi417Hwi417

262

1 Answer
1

active

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0

Here is an example of using dd to trigger a shell command whenever something is read from stdin, whether terminated by newline or not:

{

   printf %s not-nl-terminated

   sleep 1

   printf %s nl-terminated

   sleep 1

   printf 'binary1junk'

} | 

while : ; do

   input=$(dd bs=1G count=1 status=none)

   [ "$input" ] || break

   printf 'input of size %dn' "${#input}" 

done

will give

input of size 17

input of size 13

input of size 11

This snippet from the standard spec may help understand dd's behavior when used with bs= but no ibs=, obs= or conv=:

If the bs= expr operand is
specified and no conversions other than sync, noerror, or notrunc
are requested, the data returned from each input block shall be
written as a separate output block; if the read returns less than a
full block and the sync conversion is not specified, the resulting
output block shall be the same size as the input block. If the bs=
expr operand is not specified, or a conversion other than sync,
noerror, or notrunc is requested, the input shall be processed and
collected into full-sized output blocks until the end of the input
is reached.

share

edited 43 secs ago

answered 6 mins ago

mosvymosvy

11.1k11340

add a comment | 

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0

Here is an example of using dd to trigger a shell command whenever something is read from stdin, whether terminated by newline or not:

{

   printf %s not-nl-terminated

   sleep 1

   printf %s nl-terminated

   sleep 1

   printf 'binary1junk'

} | 

while : ; do

   input=$(dd bs=1G count=1 status=none)

   [ "$input" ] || break

   printf 'input of size %dn' "${#input}" 

done

will give

input of size 17

input of size 13

input of size 11

This snippet from the standard spec may help understand dd's behavior when used with bs= but no ibs=, obs= or conv=:

If the bs= expr operand is
specified and no conversions other than sync, noerror, or notrunc
are requested, the data returned from each input block shall be
written as a separate output block; if the read returns less than a
full block and the sync conversion is not specified, the resulting
output block shall be the same size as the input block. If the bs=
expr operand is not specified, or a conversion other than sync,
noerror, or notrunc is requested, the input shall be processed and
collected into full-sized output blocks until the end of the input
is reached.

share

edited 43 secs ago

answered 6 mins ago

mosvymosvy

11.1k11340

add a comment | 

0

Here is an example of using dd to trigger a shell command whenever something is read from stdin, whether terminated by newline or not:

{

   printf %s not-nl-terminated

   sleep 1

   printf %s nl-terminated

   sleep 1

   printf 'binary1junk'

} | 

while : ; do

   input=$(dd bs=1G count=1 status=none)

   [ "$input" ] || break

   printf 'input of size %dn' "${#input}" 

done

will give

input of size 17

input of size 13

input of size 11

This snippet from the standard spec may help understand dd's behavior when used with bs= but no ibs=, obs= or conv=:

If the bs= expr operand is
specified and no conversions other than sync, noerror, or notrunc
are requested, the data returned from each input block shall be
written as a separate output block; if the read returns less than a
full block and the sync conversion is not specified, the resulting
output block shall be the same size as the input block. If the bs=
expr operand is not specified, or a conversion other than sync,
noerror, or notrunc is requested, the input shall be processed and
collected into full-sized output blocks until the end of the input
is reached.

share

edited 43 secs ago

answered 6 mins ago

mosvymosvy

11.1k11340

add a comment | 

Here is an example of using dd to trigger a shell command whenever something is read from stdin, whether terminated by newline or not:

{

   printf %s not-nl-terminated

   sleep 1

   printf %s nl-terminated

   sleep 1

   printf 'binary1junk'

} | 

while : ; do

   input=$(dd bs=1G count=1 status=none)

   [ "$input" ] || break

   printf 'input of size %dn' "${#input}" 

done

will give

input of size 17

input of size 13

input of size 11

This snippet from the standard spec may help understand dd's behavior when used with bs= but no ibs=, obs= or conv=:

If the bs= expr operand is
specified and no conversions other than sync, noerror, or notrunc
are requested, the data returned from each input block shall be
written as a separate output block; if the read returns less than a
full block and the sync conversion is not specified, the resulting
output block shall be the same size as the input block. If the bs=
expr operand is not specified, or a conversion other than sync,
noerror, or notrunc is requested, the input shall be processed and
collected into full-sized output blocks until the end of the input
is reached.

share

edited 43 secs ago

answered 6 mins ago

mosvymosvy

11.1k11340

{

   printf %s not-nl-terminated

   sleep 1

   printf %s nl-terminated

   sleep 1

   printf 'binary1junk'

} | 

while : ; do

   input=$(dd bs=1G count=1 status=none)

   [ "$input" ] || break

   printf 'input of size %dn' "${#input}" 

done

input of size 17

input of size 13

input of size 11

share

edited 43 secs ago

answered 6 mins ago

mosvymosvy

11.1k11340

answered 6 mins ago

mosvymosvy

11.1k11340

answered 6 mins ago

mosvymosvy

11.1k11340