Shell Programming and Scripting

Hi,
I want to grep for a certain string in a file and depending on whether I find the string or not (depending on value of $?) I want to run an operation (if statement). How do I do this?

$? returns the status of the previous command if it is successfull then 0 else some other return code.

Code:

grep "pattern" "filename"
if [[ $? = 0 ]]; then
echo "something" 
else
--
fi

Code:

grep "String to find" filetosearch >/dev/null

if [ $? -eq "0" ]
then
  statement when string found
else
  statemnet when string not found
fi

A simpler way would be to use the || operator.

Code:

grep 'regex' buf && echo ':-)' || echo ':-('

OR

Code:

if grep -q 'regex' buf
then
    # statements
else
   # statements
fi

Thanks it works

I am trying something very similar but want to take the input from another text file, looping through it line by line. and then have some thing like

if [ $? -eq "0" ]
then
echo $line
else
echo $line>somefile.txt
fi


that way everything it finds would be output to the screen and everything that it doesn't could go to some text file.

so far i have this script, but it doesn't work?

#!/bin/bash

if [ ! $2 ]; then
echo missing arguments\(s\)
echo arch_data_comparison.sh \<archive_text\> \<database_text\>
exit 1
fi


ARCHIVE=$1
DATABASE=$2

exec 3<&0
exec 0<$DATABASE
while read line
do
fgrep $line $ARCHIVE
#if [ $? -eq 0 ] ; then echo $line ; else echo $line not found ; fi
done

exec 0<&3
exit 0