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Using GREP in IF Statement

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# 1  
Old 05-15-2013
Using GREP in IF Statement
Hello All,
I have 2 different pieces of code, I am confused why the Code1 is giving me the correct result where as the Code2 is not giving me correct result. It gives me always result as "Failure" irrespective of the "ERROR" word exists in logfile or not. may I know the reason why? I am using Bash shell in Linux OS.

Code1:
Code:
#!/bin/bash
sqlplus -s FCSDWH_STG/FCSDWH_STG@dwdev <<EOF > /home/infrmtca/bin/logfile
exec today_is;
EOF
        if `grep -q "ERROR" /home/infrmtca/bin/logfile` ;
        then
                echo "Success"
        else
                echo "Failure"
        fi

Code2:
Code:
#!/bin/bash
sqlplus -s FCSDWH_STG/FCSDWH_STG@dwdev <<EOF > /home/infrmtca/bin/logfile
exec today_is;
EOF
        if [ `grep -q "ERROR" /home/infrmtca/bin/logfile` ]
        then
                echo "Success"
        else
                echo "Failure"
        fi

My content of "/home/infrmtca/bin/logfile" is below
Code:
BEGIN today_is; END;

      *
ERROR at line 1:
ORA-06550: line 1, column 7:
PLS-00905: object FCSDWH_STG.TODAY_IS is invalid
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored

Thank you
# 2  
Old 05-15-2013
I assume you want to print message: Failure when you find the pattern: ERROR in your file.

Few corrections and modifications:
Code:
if grep -q "ERROR" /home/infrmtca/bin/logfile 
then
      echo "Failure"
else
      echo "Success"
fi

# 3  
Old 05-15-2013
Quote:
Originally Posted by Yoda
I assume you want to print message: Failure when you find the pattern: ERROR in your file.

Few corrections and modifications:
Code:
if grep -q "ERROR" /home/infrmtca/bin/logfile 
then
      echo "Failure"
else
      echo "Success"
fi

But why is it not working when I put the same in [] like [if grep -q "ERROR" /home/infrmtca/bin/logfile]

Error:
Code:
/home/infrmtca/bin/test.sh: line 5: [: too many arguments
Failure

# 4  
Old 05-15-2013
Quote:
Originally Posted by Ariean
But why is it not working when I put the same in [] like [if grep -q "ERROR" /home/infrmtca/bin/logfile]
Please note that square brackets [] that contain the statement are a synonym for the 'test' command.

So it is expecting a valid expression and it is failing because the command that you put inside doesn't meet the criteria.

This is why you don't need a square bracket [] to wrap the command.

The grep command returns the exit status 0 or non-zero which if statement can check and transfer the control to corresponding action.
# 5  
Old 05-23-2013
(1)
Quote:
Originally Posted by Yoda
Please note that square brackets [] that contain the statement are a synonym for the 'test' command.

So it is expecting a valid expression and it is failing because the command that you put inside doesn't meet the criteria.

This is why you don't need a square bracket [] to wrap the command.

The grep command returns the exit status 0 or non-zero which if statement can check and transfer the control to corresponding action.
Isn't greping for a string "ERROR" is also a test? what do you mean by test? you mean comparing 2 variables or values using -eq for numbers and == for strings or a -z or -n for zero & nonzero byte strings, something like that...Can you please explain a bit more with example

(2) I am trying the below script to check 2 conditions

Code:
#!/bin/bash
PATH="/db_apps/informatica/infa951/server/infa_shared/BWParam/wf_GenerateXMLDataFile.txt"
UNINUM="92500"
echo $UNINUM

        if  /bin/grep -q "UNINUM" $PATH -a -z ${UNINUM}
        then
                echo "success"
        else
                echo "failure"
        fi

But it always returns success, i am confused.

Thank you.
Last edited by Ariean; 05-23-2013 at 03:33 PM..
# 6  
Old 05-23-2013
Code:
if [ 4 = 4 ]
then
  echo "true"
fi

is the same as
Code:
if test 4 = 4
then
  echo "true"
fi

grep, like test, sets an exit status that "if" can use.
But grep is a different command.

Indeed [ ] is not an operator; the [ is the test command plus it wants a ] as last argument.
Code:
type test
test is a shell builtin
type \[
[ is a shell builtin

Last edited by MadeInGermany; 05-23-2013 at 03:46 PM..
# 7  
Old 05-23-2013
Is there a way for me to combine a grep command and an expression statement and pass the result to IF statement like below. I am still trying to make the below script work.

Code:
#!/bin/bash
PATH="/db_apps/informatica/infa951/server/infa_shared/BWParam/wf_GenerateXMLDataFile.txt"
UNINUM="92500"
echo $UNINUM

        if  /bin/grep -q "UNINUM" $PATH -a -z ${UNINUM}
      #if  [ `/bin/grep -q "UNINUM" $PATH` -a -z ${UNINUM} ]
        then
                echo "success"
        else
                echo "failure"
        fi

---------- Post updated at 03:36 PM ---------- Previous update was at 03:32 PM ----------

Quote:
Originally Posted by Ariean
Is there a way for me to combine a grep command and an expression statement and pass the result to IF statement like below. I am still trying to make the below script work.

Code:
#!/bin/bash
PATH="/db_apps/informatica/infa951/server/infa_shared/BWParam/wf_GenerateXMLDataFile.txt"
UNINUM="92500"
echo $UNINUM

        if  /bin/grep -q "UNINUM" $PATH -a -z ${UNINUM}
      #if  [ `/bin/grep -q "UNINUM" $PATH` -a -z ${UNINUM} ]
        then
                echo "success"
        else
                echo "failure"
        fi

I think i got it

Code:
#!/bin/bash
PATH="/db_apps/informatica/infa951/server/infa_shared/BWParam/wf_GenerateXMLDataFile.txt"
UNINUM="92500"
echo $UNINUM

        if  ! `/bin/grep -q "UNINUM" $PATH` && [ ! -z ${UNINUM} ]
        then
                echo "success"
        else
                echo "failure"
        fi
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