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KSH problem - how do i redirect three times?

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Top Forums Shell Programming and Scripting KSH problem - how do i redirect three times?
# 8  
Old 09-30-2008
Quote:
Originally Posted by mjays
the problem is, i need the script to exit if the ls command fails, but all it does is display the error and then write to the log file.

this is the ls command and the code after it

Code:
ls -lR ${BUILD_CODE} 2>&1 >${REL_FILES}/${RELNO}.txt | tee -a ${LOGFILE}
if [ $? -ne 0 ]
   then
       exit
fi

so you see, the tee command is probably successful which gives me a $status of 0.

how do i interogate the error from the ls command when it's tucked in way back there?
In bash, you can turn on the option "pipefail", and $? will return the result of the last command to fail in the pipeline (otherwise, it will return the result of the last command OF the pipeline). Use "set -o pipefail" to turn this feature on. Observe:
Code:
false | cat; echo $?
0
$ set -o pipefail
$ false | cat; echo $?
1

Otherwise, you have to do tricks like:
Code:
/bin/ls $FILE >$TMP_FILE_2 2>&1
res=$?
cat $TMP_FILE_2 >>$LOGFILE
if [ $res -ne 0 ]; then 
  exit
fi

# 9  
Old 09-30-2008
Quote:
Originally Posted by otheus
In bash, you can turn on the option "pipefail", and $? will return the result of the last command to fail in the pipeline (otherwise, it will return the result of the last command OF the pipeline). Use "set -o pipefail" to turn this feature on. Observe:
Code:
false | cat; echo $?
0
$ set -o pipefail
$ false | cat; echo $?
1

Otherwise, you have to do tricks like:
Code:
/bin/ls $FILE >$TMP_FILE_2 2>&1
res=$?
cat $TMP_FILE_2 >>$LOGFILE
if [ $res -ne 0 ]; then 
  exit
fi

yeah, i've already considered the extra check to see if the file was created. i was hoping there was a more direct solution using a method i've never seen before. a super advanced system admin/unix expert method.
Last edited by mjays; 09-30-2008 at 11:36 AM.. Reason: correcting a typo.
# 10  
Old 09-30-2008
Quote:
Originally Posted by mjays
yeah, i've already considered the extra check to see if the file was created. i was hoping there was a more direct solution using a method i've never seen before. a super advanced system admin/unix expert method.
Odd, is it not?

So can you use bash? Maybe ksh has a similar option?
# 11  
Old 09-30-2008
Quote:
Originally Posted by mjays
a super advanced system admin/unix expert method.
;-))))

In fact there is and i am glad to be able to explain - once in a lifetime - "super advanced system admin expert methods" to the audience: You can redirect output streams with the "exec" command:

exec 2>output.stderr

Will redirect every output of every subsequent command to output.stderr.

This way you do not have to worry about truncating the file at all:


Code:
exec 2>output.stderr     # truncates the file and redirects stderr to it
job1
job2
job3
exec 2>&-                # closes stderr and removes the redirection

is equivalent to

Code:
job1 2> output.stderr
job2 2>> output.stderr
job3 2>> output.stderr

I hope this helps.

bakunin
# 12  
Old 10-01-2008
Quote:
Originally Posted by bakunin
;-))))

In fact there is and i am glad to be able to explain - once in a lifetime - "super advanced system admin expert methods" to the audience: You can redirect output streams with the "exec" command:

exec 2>output.stderr

Will redirect every output of every subsequent command to output.stderr.

This way you do not have to worry about truncating the file at all:


Code:
exec 2>output.stderr     # truncates the file and redirects stderr to it
job1
job2
job3
exec 2>&-                # closes stderr and removes the redirection

is equivalent to

Code:
job1 2> output.stderr
job2 2>> output.stderr
job3 2>> output.stderr

I hope this helps.

bakunin
erm...where does that fit in with my bit of code?

Code:
ls -lR ${BUILD_CODE} 2>&1 >${REL_FILES}/${RELNO}.txt | tee -a ${LOGFILE}
if [ $? -ne 0 ]
   then
       echo "ERROR - release file creation failed 
       exit
fi

i've tried not to be stupid and figure out how to use your solution but i give in.
# 13  
Old 10-01-2008
"super advanced system admin expert methods" means writing answers without first understanding the question. Smilie

Seriously, at the *beginning* of the script, you could do something like this:

Code:
exec >standard.out 2>error.out

Every time there's an error, you stop the script and output the error.out file. However, it doesn't deal with automatically printing the normal output. However, you could go to another terminal and run:
Code:
tail -f standard.out

but I don't think that suits your purpose.
# 14  
Old 10-01-2008
you are using err file (redirecting the error to stderr)wright?
lets take

ls data >err 2>&1 | tee -a somefile
if [ ! -s err ]
then
{do whatever you want}
fi

here as per the code the err file will load with some error message when failure occurs in ls.
is it feasible?
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