Incremental number in shell script on each loop

Question

#!/bin/bash

echo SCRIPT: $0
echo "Enter Customer Order Ref (e.g. 100018)"
read P_CUST_ORDER_REF
echo "Enter DU Id (e.g. 100018)"
read P_DU_ID

P_ORDER_ID=${P_CUST_ORDER_REF}${P_DU_ID}


#Loop through all XML files in the current directory
for f in *.xml
do
  #Increment P_CUST_ORDER_REF here
done

Inside the for loop how can i increment P_CUST_ORDER_REF by 1 every time it loops

so it READs 10000028 uses it on first loop
2nd 10000029
3rd 10000030
4th 10000031

Prince John Wesley · Accepted Answer · 2012-06-12 15:33:49Z

7

((P_CUST_ORDER_REF+=1))

or

let P_CUST_ORDER_REF+=1

answered Jun 12, 2012 at 15:33

Prince John Wesley

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mouviciel · Accepted Answer · 2012-06-12 15:12:42Z

6

P_CUST_ORDER_REF=$((P_CUST_ORDER_REF+1))

answered Jun 12, 2012 at 15:12

mouviciel

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1 Comment

William Pursell Over a year ago

+1 for portability. Note that you can also do: : $(( P_CUST_ORDER_REF += 1 )) or use a ++ operator.

Dennis Williamson · Accepted Answer · 2012-06-12 16:13:30Z

2

You can use the post-increment operator:

(( P_CUST_ORDER_REF++ ))

I recommend:

habitually using lowercase or mixed case variable names to avoid potential name collision with shell or environment variables
quoting all variables when they are expanded
usually using -r with read to prevent backslashes from being interpreted as escapes
validating user input

For example:

#!/bin/bash
is_pos_int () {
    [[ $1 =~ ^([1-9][0-9]*|0)$ ]]
}

echo "SCRIPT: $0"

read -rp 'Enter Customer Order Ref (e.g. 100018)' p_cust_order_ref
is_pos_int "$p_cust_order_ref"

read -rp 'Enter DU Id (e.g. 100018)' p_du_id
is_pos_int "$p_dui_id"

p_order_id=${p_cust_order_ref}${p_du_id}

#Loop through all XML files in the current directory
for f in *.xml
do
    (( p_cust_order_ref++ ))
done

edited Jun 12, 2012 at 16:13

answered Jun 12, 2012 at 16:02

Dennis Williamson

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