How to compare that file name is empty?

Shell Programming and Scripting
1

i am finding some pattern this way..

fname=`grep -w "^$index" $HOME/UnixCw/backup/Path.txt`

how to check that fname is empty i.e. if pattren doesnt found then i want to do other operations....

2

look at the -s file test operator

3

I tried but its not working...can you please elaborate more..I am very new to unix...sorry for trouble

4 
if [ -z $fname ]
then
    # do something
fi

Read the man page for test.

5

ignore my post about -s. I misunderstood what you were trying to do. there is no need to have a $fname variable if your just testing for a match.

if grep -q -w "^$index" $HOME/UnixCw/backup/Path.txt
then
   #do something
fi
6

if [ -z $variable ]

This will check whether the $variable is Null.

7

You could also do:

grep -q -w "^$index" $HOME/UnixCw/backup/Path.txt

if [ ! $? = "0" ]
then
    #dowhatever
fi

If your grep finds the string the exit status will be 0 and you can branch based upon that, or the reverse.

8

you can also use grep's exit status $? to check if there is a pattern or not. if there is a pattern exit value is 0, otherwise 1.

mo@mo-laptop:~$ ls | grep scripts
scripts
mo@mo-laptop:~$ echo $?
0
mo@mo-laptop:~$ ls | grep nofilehere
mo@mo-laptop:~$ echo $?
1

just put it in an if-then statement.

in bash:

grep something
if [ $? == 1 ]; then
      do something
fi

---------- Post updated at 11:35 PM ---------- Previous update was at 11:34 PM ----------

oops, someone beat me to it