如何检查字符串的第一个字符是否为bash中的数字？

Question

I am writing an xml element in bash. I need to replace some strings which will start with numbers into something that starts with an character, so it is a valid XML tag (remember xml tags cannot start with alpha numeric characters).

For Example,

  str = 192.16.76.52,1001

which is not a valid xml tag, ie i cannot do

<192.16.76.52,1001>
.....
</192.16.76.52,1001>

So, I am planning to detect if it is a number and replace it with something like

IP192.16.76.52

I know I can do it with IFS, but it might take long time and extra code.

Since you know the main problem, feel free to comment or offer suggestions.

Thanks

Answer 1

The RHS of = in [[ takes a glob pattern.

$ [[ 123 = [0-9]* ]] ; echo $?
0
$ [[ foo = [0-9]* ]] ; echo $?
1