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exit status of command in a pipe line

 
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# 8  
Old 10-18-2007
Bug Can someone explain me whats this code is doing?
This code is too elegant for me, please explain what it does and how?

Quote:
Originally Posted by Perderabo
This depends on the shell. ksh can smash through that wall by moving the "tail -15" to a co-process. I don't know that cleartool command so I'll use "cat /etc/passwd" for my example:
Code:
#! /usr/bin/ksh
exec 4>&1
tail -5 >&4 |&
exec >&p
cat /etc/passwd
exitcode=$?
exec >&- >&4
wait
echo exitcode = $exitcode
exit 0

# 9  
Old 10-18-2007
Quote:
Originally Posted by topcat8
Hi,

I am trying to test the exit status of the cleartool lsvtree statement below, but it doesn't seem to be working due to the tail pipe, which it is testing instead. Is there a way around this without adding a tonne of new code?
[...]
bash and ksh93 have the pipefail option:

Code:
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo $?
0
bash 3.2.25(17)$ set -o pipefail
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo $?
2


bash and zsh have the PIPESTATUS/pipestatus array/variable:

Code:
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo $PIPESTATUS
2
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo ${PIPESTATUS[@]}
2 0

Code:
zsh 4.3.4% ls x|tail
ls: cannot access x: No such file or directory
zsh 4.3.4% echo $pipestatus
2 0

# 10  
Old 10-18-2007
set -o pipefail not available on sunos, $PIPESTATUS works on bash not on ksh
Quote:
Originally Posted by radoulov
bash and ksh93 have the pipefail option:

Code:
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo $?
0
bash 3.2.25(17)$ set -o pipefail
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo $?
2


bash and zsh have the PIPESTATUS/pipestatus array/variable:

Code:
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo $PIPESTATUS
2
bash 3.2.25(17)$ ls x|tail
ls: cannot access x: No such file or directory
bash 3.2.25(17)$ echo ${PIPESTATUS[@]}
2 0

Code:
zsh 4.3.4% ls x|tail
ls: cannot access x: No such file or directory
zsh 4.3.4% echo $pipestatus
2 0

set -o pipefail doesnt seem to work on SunOS 5.8

Code:
bash-2.03$ uname
SunOS
bash-2.03$ set -o pipefail
bash: set: pipefail: unknown option name

echo $PIPESTATUS works on bash but not on ksh

Code:
bash-2.05$ ls -l rakesh | tail -5
rakesh: No such file or directory
bash-2.05$ echo $PIPESTATUS
2

# 11  
Old 10-19-2007
Quote:
Originally Posted by rakeshou
set -o pipefail doesnt seem to work on SunOS 5.8

Code:
bash-2.03$ uname
SunOS
bash-2.03$ set -o pipefail
bash: set: pipefail: unknown option name

[...]
Yes,
it's a new feature of bash Bash-3.0.

Quote:
echo $PIPESTATUS works on bash but not on ksh

Code:
bash-2.05$ ls -l rakesh | tail -5
rakesh: No such file or directory
bash-2.05$ echo $PIPESTATUS
2

Hm ...., I said bash and zsh.
I said that the pipefail option is available in ksh93 (not ksh88)!
 
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