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-1

I am writing script in shell and it's something like:

temp=0
while true; do
 case "a" in
 a) temp=5; ;;
 esac
 break
done | echo "$temp"

( temp value is condition for if in subshell and | (pipe) is needed as stdout redirect to stdin)
and I need in temp 5 but I got 0 in echo. Any way to preserve value inside case (posixly correct without tempfile)?

shell

share|improve this question

edited yesterday

Darman41

asked yesterday

Darman41Darman41

11

New contributor

Darman41 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  In while true; do case "a" in a) temp=5; ;; esac; break; done | echo "$temp", the $temp on the right hand side of the pipe is evaluated before the while loop is executed.
  
  – William Pursell
  yesterday
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Please show what you're actually trying to do in the right side of the pipe. Piping to echo doesn't make sense since echo doesn't read from stdin. We need to know what you're really doing because the answers will vary based on what you really need.
  
  – John Kugelman
  yesterday
  

  
  
  
  

add a comment | 

-1

I am writing script in shell and it's something like:

temp=0
while true; do
 case "a" in
 a) temp=5; ;;
 esac
 break
done | echo "$temp"

( temp value is condition for if in subshell and | (pipe) is needed as stdout redirect to stdin)
and I need in temp 5 but I got 0 in echo. Any way to preserve value inside case (posixly correct without tempfile)?

shell

share|improve this question

edited yesterday

Darman41

asked yesterday

Darman41Darman41

11

New contributor

Darman41 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  In while true; do case "a" in a) temp=5; ;; esac; break; done | echo "$temp", the $temp on the right hand side of the pipe is evaluated before the while loop is executed.
  
  – William Pursell
  yesterday
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Please show what you're actually trying to do in the right side of the pipe. Piping to echo doesn't make sense since echo doesn't read from stdin. We need to know what you're really doing because the answers will vary based on what you really need.
  
  – John Kugelman
  yesterday
  

  
  
  
  

add a comment | 

I am writing script in shell and it's something like:

temp=0
while true; do
 case "a" in
 a) temp=5; ;;
 esac
 break
done | echo "$temp"

( temp value is condition for if in subshell and | (pipe) is needed as stdout redirect to stdin)
and I need in temp 5 but I got 0 in echo. Any way to preserve value inside case (posixly correct without tempfile)?

shell

share|improve this question

edited yesterday

Darman41

asked yesterday

Darman41Darman41

11

New contributor

Darman41 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

temp=0
while true; do
 case "a" in
 a) temp=5; ;;
 esac
 break
done | echo "$temp"

share|improve this question

edited yesterday

Darman41

asked yesterday

Darman41Darman41

11

New contributor

Darman41 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited yesterday

Darman41

asked yesterday

Darman41Darman41

11

New contributor

Darman41 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked yesterday

Darman41Darman41

11

New contributor

Darman41 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked yesterday

Darman41Darman41

11

1 Answer
1

active

oldest

votes

0

Do you want it like this? Prints 5 and 0.

#!/bin/sh
temp=0
while true; do
 case "a" in
 a) temp=5; echo "$temp" ;;
 esac
 break
done | cat

echo "temp unchanged because of subshell $temp"

Would this help you, filtering out your status?
I still don't get why you need a pipe and how you expect the other command you pipe into to react on a status. It's just not the way it works. You evaluate conditions in your script and call commands accordingly.

#!/bin/sh
filter()
 data=''
 while read line; do
 case "$line" in
 temp=5) temp=5 ;;
 *) data=$(printf '%sn' "$data"; printf '%sn' "$line") ;;
 esac
 done

 if [ "$temp" -eq 5 ]; then
 echo "do this 5 with data"
 else
 echo "do that other with data"
 echo "$data"
 fi


temp=0
while true; do
 case "a" in
 a) temp=5; printf 'temp=%sn' "$temp"; for i in $(seq 1 30); do echo "30 lines"; done ;;
 esac
 break
done | filter

echo "temp unchanged because of subshell $temp"

share|improve this answer

edited yesterday

answered yesterday

xenosonxenoson

533

New contributor

xenoson is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Unfortunately not, I need to stdout and stdin unchanged. Point is to pass variable and stdout to subshell
  
  – Darman41
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  stdout and stdin unchanged? So no pipe? Because in your question you say you want to pipe?
  
  – xenoson
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I need to pipe stdout (30 lines) to stdin (30 lines) and pass that variable, which decide, what should happen with those lines
  
  – Darman41
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Maybe use another file descriptor.
  
  – xenoson
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  sadly I don't have those 20 lines in file and I am not allowed to create temporarily file
  
  – Darman41
  yesterday
  

  
  
  
  

 | 
show 2 more comments

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0

Do you want it like this? Prints 5 and 0.

#!/bin/sh
temp=0
while true; do
 case "a" in
 a) temp=5; echo "$temp" ;;
 esac
 break
done | cat

echo "temp unchanged because of subshell $temp"

Would this help you, filtering out your status?
I still don't get why you need a pipe and how you expect the other command you pipe into to react on a status. It's just not the way it works. You evaluate conditions in your script and call commands accordingly.

#!/bin/sh
filter()
 data=''
 while read line; do
 case "$line" in
 temp=5) temp=5 ;;
 *) data=$(printf '%sn' "$data"; printf '%sn' "$line") ;;
 esac
 done

 if [ "$temp" -eq 5 ]; then
 echo "do this 5 with data"
 else
 echo "do that other with data"
 echo "$data"
 fi


temp=0
while true; do
 case "a" in
 a) temp=5; printf 'temp=%sn' "$temp"; for i in $(seq 1 30); do echo "30 lines"; done ;;
 esac
 break
done | filter

echo "temp unchanged because of subshell $temp"

share|improve this answer

edited yesterday

answered yesterday

xenosonxenoson

533

New contributor

xenoson is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Unfortunately not, I need to stdout and stdin unchanged. Point is to pass variable and stdout to subshell
  
  – Darman41
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  stdout and stdin unchanged? So no pipe? Because in your question you say you want to pipe?
  
  – xenoson
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I need to pipe stdout (30 lines) to stdin (30 lines) and pass that variable, which decide, what should happen with those lines
  
  – Darman41
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Maybe use another file descriptor.
  
  – xenoson
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  sadly I don't have those 20 lines in file and I am not allowed to create temporarily file
  
  – Darman41
  yesterday
  

  
  
  
  

 | 
show 2 more comments

0

Do you want it like this? Prints 5 and 0.

#!/bin/sh
temp=0
while true; do
 case "a" in
 a) temp=5; echo "$temp" ;;
 esac
 break
done | cat

echo "temp unchanged because of subshell $temp"

Would this help you, filtering out your status?
I still don't get why you need a pipe and how you expect the other command you pipe into to react on a status. It's just not the way it works. You evaluate conditions in your script and call commands accordingly.

#!/bin/sh
filter()
 data=''
 while read line; do
 case "$line" in
 temp=5) temp=5 ;;
 *) data=$(printf '%sn' "$data"; printf '%sn' "$line") ;;
 esac
 done

 if [ "$temp" -eq 5 ]; then
 echo "do this 5 with data"
 else
 echo "do that other with data"
 echo "$data"
 fi


temp=0
while true; do
 case "a" in
 a) temp=5; printf 'temp=%sn' "$temp"; for i in $(seq 1 30); do echo "30 lines"; done ;;
 esac
 break
done | filter

echo "temp unchanged because of subshell $temp"

share|improve this answer

edited yesterday

answered yesterday

xenosonxenoson

533

New contributor

xenoson is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Unfortunately not, I need to stdout and stdin unchanged. Point is to pass variable and stdout to subshell
  
  – Darman41
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  stdout and stdin unchanged? So no pipe? Because in your question you say you want to pipe?
  
  – xenoson
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I need to pipe stdout (30 lines) to stdin (30 lines) and pass that variable, which decide, what should happen with those lines
  
  – Darman41
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Maybe use another file descriptor.
  
  – xenoson
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  sadly I don't have those 20 lines in file and I am not allowed to create temporarily file
  
  – Darman41
  yesterday
  

  
  
  
  

 | 
show 2 more comments

Do you want it like this? Prints 5 and 0.

#!/bin/sh
temp=0
while true; do
 case "a" in
 a) temp=5; echo "$temp" ;;
 esac
 break
done | cat

echo "temp unchanged because of subshell $temp"

Would this help you, filtering out your status?
I still don't get why you need a pipe and how you expect the other command you pipe into to react on a status. It's just not the way it works. You evaluate conditions in your script and call commands accordingly.

#!/bin/sh
filter()
 data=''
 while read line; do
 case "$line" in
 temp=5) temp=5 ;;
 *) data=$(printf '%sn' "$data"; printf '%sn' "$line") ;;
 esac
 done

 if [ "$temp" -eq 5 ]; then
 echo "do this 5 with data"
 else
 echo "do that other with data"
 echo "$data"
 fi


temp=0
while true; do
 case "a" in
 a) temp=5; printf 'temp=%sn' "$temp"; for i in $(seq 1 30); do echo "30 lines"; done ;;
 esac
 break
done | filter

echo "temp unchanged because of subshell $temp"

share|improve this answer

edited yesterday

answered yesterday

xenosonxenoson

533

New contributor

xenoson is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

#!/bin/sh
temp=0
while true; do
 case "a" in
 a) temp=5; echo "$temp" ;;
 esac
 break
done | cat

echo "temp unchanged because of subshell $temp"

#!/bin/sh
filter()
 data=''
 while read line; do
 case "$line" in
 temp=5) temp=5 ;;
 *) data=$(printf '%sn' "$data"; printf '%sn' "$line") ;;
 esac
 done

 if [ "$temp" -eq 5 ]; then
 echo "do this 5 with data"
 else
 echo "do that other with data"
 echo "$data"
 fi


temp=0
while true; do
 case "a" in
 a) temp=5; printf 'temp=%sn' "$temp"; for i in $(seq 1 30); do echo "30 lines"; done ;;
 esac
 break
done | filter

echo "temp unchanged because of subshell $temp"

share|improve this answer

edited yesterday

answered yesterday

xenosonxenoson

533

New contributor

xenoson is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered yesterday

xenosonxenoson

533

New contributor

xenoson is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered yesterday

xenosonxenoson

533