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For loop problem

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# 1  
Old 02-03-2010
For loop problem
Hi,
I have a simple for loop, given below,thats giving me trouble. I am new to shell scripting and I don't know what I am missing. I appreciate your help.

Code:
a=1
b=5
for(a=1;a<=b;a++)
do
        echo "Hello a"
done


Thanks!!
Last edited by Franklin52; 02-09-2010 at 03:05 PM.. Reason: Please use code tags!!
# 2  
Old 02-03-2010
Search forums for examples of for loops. You will easily find the answer to your question,
# 3  
Old 02-03-2010
Quote:
Originally Posted by nagin
Hi,
I have a simple for loop, given below,thats giving me trouble. I am new to shell scripting and I don't know what I am missing. I appreciate your help.

a=1
b=5
for(a=1;a<=b;a++)
[/CODE]

First, that is not standard shell syntax for a loop.

The syntax is:

Code:
for VAR in <LIST>

Some shells have a non-standard extension, which is probably what you want:
Code:
for ((a=1;a<=b;a++))

Quote:
Code:
do
        echo "Hello a"


That will print a literal 'a'; to reference a variable, precede it with a dollar sign:
Code:
echo "Hello $a"

Quote:
[CODE]
done
# 4  
Old 02-03-2010
If available, you can use seq
Code:
for a in $(seq 1 $b)
do ...
# the "1" is optional (seq strats by default at 1)
for a in $(seq $b)

# 5  
Old 02-03-2010
Quote:
Originally Posted by frans
If available, you can use seq
Code:
for a in $(seq 1 $b)
do ...
# the "1" is optional (seq strats by default at 1)
for a in $(seq $b)


There is no need for an external command (seq):

Code:
n=0
max=5
while [ $n -lt $max ]
do
  : do whatever
  n=$(( $n + 1 ))
done

# 6  
Old 02-09-2010
Quote:
Originally Posted by cfajohnson

Some shells have a non-standard extension, which is probably what you want:
Code:
for ((a=1;a<=b;a++))

Thank you very much, The double parenthesis worked.
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