Bash scripting help needed

ZAMO · 08-05-2008, 06:42 AM

Hi all,

I need a help is scripting. Can someone give me the equivalent for loop for the following "C" format in BASH:

Code:

i=10

for(i=0;i<10;i++)
{
executable cmd
}

Thanks

arizonagroovejet · 08-05-2008, 07:08 AM

I don't understand what the i=10 line is supposed to do in your example.
If you want to run the command whatever 10 times then try

Code:

for i in `seq 1 10`;do 
whatever
done

colucix · 08-05-2008, 07:13 AM

You can explicitly loop over a sequence of numbers or strings, as in

Code:

for i in 1 2 3 4 5 6 7 8 9 10
do
  echo $i
done

or you can generate the sequence using command substitution:

Code:

for i in $(seq 1 10)
do
  echo $i
done

Finally recent versions of bash permit the usage of a C-like loop, using the arithmetic operator, as in

Code:

for (( i = 1; i <= 10; i++ ))
do
  echo $i
done

The Advanced Bash Scripting Guide explains it all.

pwc101 · 08-05-2008, 07:17 AM

If you have bash version 3 or above, you can do:

Code:

for i in {0..10}; do 
   echo $i
done

Otherwise, if you have an array of values:

Code:

some_array=(1 2 3 4 5 6 7 8 9 10)
for ((i=0; i<${#some_array[@]}; i++)); do
   echo $i
done

That array can contain words or numbers. The ${#some_array[@]} counts the number of elements in the array.

edit: beaten to it by colucix!

ZAMO · 08-05-2008, 07:23 AM

Thank you for all your Replies.

Sorry I made a mistake in my post.

Code:

i=10

But "i" is a variable.
am got the value of "i" from another output

Code:

i=$(cat file1 |wc -l)

The value of i can vary. Can someone help me to do the for loop for the variable "i" for the same logic

pwc101 · 08-05-2008, 07:36 AM

Code:

i=(wc -l < file1)
for ((j=0; j<$i; j++)); do
   echo $j
done

ZAMO · 08-05-2008, 07:48 AM

Thank you PWC101

Its working .

ZAMO · 08-05-2008, 07:53 AM

Got struck at the next step
Am trying to compare the two files within the loop and got some error.

Code:

i=(wc -l < file1)
for ((j=0; j<$i; j++)); do
 diff `sed -n '($j)p' file1` file2 >file3  
done

How can i declare the "$j" inside sed -n 'p' file1.

ghostdog74 · 08-05-2008, 08:01 AM

if you want to compare 2 files, use diff. Otherwise, if you have special requirements, pls describe.

ZAMO · 08-05-2008, 08:07 AM

I want to surely compare 2 files..