add new character to the beginning of some lines

[peter_brickles]

Hi guys

I have a large list of uk phone numbers all of which should be 11 characters long.

They should begin with a 0 some how ever have the 0 missing is there any way to iterate though the file and add a 0 as the first character if it does not laready exist.

thanks pete

[vasa1]

You should include a few lines to illustrate what you want. The experts here will then be better placed to help you.

[peter_brickles]

list is as below

07887123456
7878345343
07070712345
799999999

the numbers that do not start with a 0 should have a 0 added to them so all file is in a standard format !

thanks

[Lars Noodén]

You can use printf in many scripting languages. Here is one example from awk.

awk '{ printf("%011d\n", $1)}' < list1.txt > list2.txt

Edit: better double check to make sure that does what you want.

[peter_brickles]

e sort of works but double zeros records already starting with zero

[Lars Noodén]

Here's a second approach.

awk '/^0/ { print $1; } ! /^0/ { print "0" $1 }' < file1.txt > file2.txt

It won't check the number length, just prepend a zero if it is missing from the start of the number.

[ICanHasNick]

if you want to examine before the change is made what the change will be like:

$> vim yourfile
:%s/^\([1-9]\)/0\1/
# if it has done what you have intended
:wq
#if not
u
:q!

[ofnuts]

The sed-based solution:

sed -re 's/^([0-9]{10})$/0\1/' <phonenums.txt

[drmrgd]

Perl solution (assuming text file with one phone number per line):

$ perl -pne 's/(.*)/0$1/ if ( ! /^0/ )' numbers.txt 
07887123456
07878345343
07070712345
0799999999