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returning status of a command

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# 1  
Old 07-12-2010
returning status of a command
Hello gurus,

Tired of using $? to view the execution status of the previous command.

how can I get the status directly?

definitely this is not working,

Code:
if [[ `grep pattern file_name` -eq 0 ]]
then
fi

Last edited by pludi; 07-12-2010 at 03:34 AM.. Reason: code tags, please..
# 2  
Old 07-12-2010
This should work
Code:
if grep -q pattern file_name
then
fi

or
Code:
if grep pattern file_name >/dev/null 2>&1
then
fi

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biglau ensameer
# 3  
Old 07-12-2010
yup, but is there a way to get a general commond/function execution status(returning number) withcout using $?

and btw, what if I use the dual square brackets, it only check if the returning value is null or non-null, rather than 0 or non-0.

So how should I get the $? directly in the if [[ ]] ?

Thank you all.
Last edited by biglau; 07-12-2010 at 04:40 AM..
# 4  
Old 07-12-2010
#grep pattern file_name
#echo $?
# 5  
Old 07-12-2010
Assuming we have a file called "file_which_does_exist" and we do not have a file called "file_which_does_not_exist" and we are looking for a string "string". There are three possible reply codes.

Code:
grep -qs "string" file_which_does_not_exist; REPLY="$?"
echo "${REPLY}"
2

grep -qs "rubbish" file_which_does_exist; REPLY="$?"
echo "${REPLY}"
1

grep -qs "string" file_which_does_exist; REPLY="$?"
echo "${REPLY}"
0

This User Gave Thanks to methyl For This Post:
biglau
# 6  
Old 07-19-2010
You are right, seems I have to write a customized function to get the returning status, like

Code:
function rt_status()
{
  eval "$1"
  return $?
}

then I can use the function like the following
Code:
if [[ rt_status "grep pattern file_name" -eq 0 ]]
then
    echo "pattern matched"
elif [[ rt_status "grep pattern file_name" -eq 1 ]]
then
    echo "Pattern unmatched"
elif [[ rt_status "grep pattern file_name" -eq 2 ]]
then
    echo "file_name not existed"
fi

See, just want to know if there is a system built-in function to replace my rt_status function to return the status of the execution for a command? I am not willing to fetch that status by $?
Last edited by Scott; 07-21-2010 at 03:15 AM.. Reason: Code tags...
This User Gave Thanks to biglau For This Post:
# 7  
Old 07-21-2010
I do not see any advantage in this. You have seen my example above without the use of $?. Why is that not usable for you? Also, why do you find the use of $? objectionable anyway?
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