nixCraft

#1 (**permalink**) 08-30-2005, 07:32 PM

Hi all,
Just wondering, how can we get the exit status of a command inside the script. Lets say...

Code:

for i in........
do command1
    command2
    command3
done

if [ $? = 0 ] 
echo "Command completed successfully"
else echo "Command failed"
fi

the $?, if placed after the loop, will print the exit status of the script. In which case, it is always......Command completed successfully.

But what I want is, if anything within the for loop fails, the exit status shall be greater than 0. in which case, it will echo .....Command failed. But this never happens

Where am I going wrong.

Thanks in advance for any help

rc

monk · #2 (**permalink**) 08-31-2005, 12:25 AM

get status in loop itself

Code:

ST=0
for i in........
do command1
    command2
    command3
    ST=$?
done 

if [ "$ST" == "0" ]; then
do
    echo "Ok"
else
    echo "Failed
done

ricc · #3 (**permalink**) 08-31-2005, 12:27 PM

Oh ! Great...
Thank you monk.

I would like to know...does it give $?=0 even if any one of the commands in the loop fails.

Thanks in advance

rockdalinux · #4 (**permalink**) 08-31-2005, 02:32 PM

Monk, your code upto for loop seems to correct but if...else..fi should be as follows :O

Code:

if [ $ST -eq 0 ]; then 
    echo "Ok" 
else 
    echo "Failed 
fi

if command syntax was incorrect as well as you used “$ST” == “0” which is for strict POSIX compliance and returns ture if the strings are equal. Since exit status is always numeric non negative value, it is better to use arithmetic binary operators such as -eq (equal to).

ricc, I think $? in loop will only useful after command3 and not useful for command2 and command1, because it will always/store command3 exit status. You can do as follows:

Code:

# exit status for all three command:
EST1=0
EST2=0
EST3=0

for i in...
do
  command1
  EST1=$?
  command2
  EST2=$?
  command3
  EST3=$?
done

[ $EST1 -ne 0 ] && echo “Command1 Ok” || echo “Command1 Failed” 
[ $EST2 -ne 0 ] && echo “Command2 Ok” || echo “Command2 Failed” 
[ $EST3 -ne 0 ] && echo “Command3 Ok” || echo “Command3 Failed”

monk · #5 (**permalink**) 08-31-2005, 07:39 PM

Opps you are right rocky, I made mistake while writing if..else code. However you can use “$ST” == “0” string based comparison and it is valid.

ricc · #6 (**permalink**) 09-01-2005, 12:53 PM

Thanks rocky,

I have stumbled upon something. I want to know, can we get the exit status of the command in the for line......
like:

Code:

#!/bin/bash
# give a directory name to the script
echo -n " Give the directory name : "
read dname
for i in $(ls dname)
do
if [ -f $i ] && [ -x $i ]
then echo " $i is an executable file"
elif [ -f $i ] && [ ! -x $i ]
then echo " $i is not an executable file"
elif [ -d $i ] 
then echo " $i is a directory"
fi
fi 
fi
done

if [ "$?" == "0" ] 
then  echo "This Script completed successfully"
else echo "This Script failed"
fi

Now, Lets say...the user typed in a directory name, that doesn't exist. Then, the remaining of the script is obviously not valid. And also, if the directory name given is not valid.....ls gives an error on the screen.

I want that anywhere, any command encounters an error, the script should echo failed.

Thanks for any and all the help.

rc

sweta · #7 (**permalink**) 09-01-2005, 02:06 PM

Here is code you wanna

Code:

#!/bin/bash
echo -n "Give the directory name : "
read dname
if [ ! -d $dname ];then
        echo "Error - $dname is not directory"
        exit 1
fi

for i in $(ls $dname)
do
if [ -f $i ] && [ -x $i ]
then echo " $i is an executable file"
elif [ -f $i ] && [ ! -x $i ]
then echo " $i is not an executable file"
elif [ -d $i ]
then echo " $i is a directory"
fi
done

if [ "$?" == "0" ]
then  echo "This Script completed successfully"
else echo "This Script failed"
fi

ricc · #8 (**permalink**) 09-01-2005, 05:01 PM

Thats good---

. Thank you Sweta.

One more thing....

Lets say....

we have something within a "for" script loop.. like:

Code:

for i in $(cat file.txt | awk ' { print $1 }'| grep -vE "( xyz|abc|^-)")
do  command 1
     command 2 
     command 3
done

and if any of the commands within (cat file.txt | awk ' { print $1 }'| grep -vE "( xyz|abc|^-)") fails, can we get an exit status of that.

can we....?. I guess when we run something within () , it spawns another sub-shell for that.

Thanks everyone...monk,rocky,vivek,sweta...everyone, for all of your unstinted support and replies.

Cheers,
rc

monk · #9 (**permalink**) 09-02-2005, 07:34 PM

You're welcome!
From man pages.

Code:

Each command in a pipeline is executed in its own subshell . The exit status of a pipeline is the exit status of the last command in the pipeline. If the reserved word `!' precedes the pipeline, the exit status is the logical negation of the exit status of the last command.

So you are right and you will get only exit status of the LAST command in pipeline, not a any one of the in (cat file.txt | awk ' { print $1 }'| grep -vE "( xyz|abc|^-)") .

Hope this clears some black clouds

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