If you are using Microsoft Windows, such as Windows XP, you can
extract a substring from a variable string using character positional
notation, i.e. %myvar:~char_skip_num%. I.e., where you have
some variable, e.g. %myvar%, you can place the
:~ operator prior to the ending % and then specify
a the number of characters to skip followed by the ending %.
E.g. from a command line if you checked the value of a user profile variable,
i.e. %userprofile%, for a user named James, you might see the
following:
C:\>echo %userprofile% C:\Documents and Settings\James
If I wanted to extract just the user's account name, i.e. James,
I could use the following:
C:\>echo %userprofile:~26% James
The "J" in James is the 27th character,
so I used 26 to have the first 26 characters skipped.
You can also specify that you only want to extract a certain number of characters by putting a comma after the number of characters to be skipped followed by the number of characters to extract. E.g, if I only wanted to extract the first 3 characters starting at position 27, I could use the following:
C:\>echo %userprofile:~26,3% Jam
If you don't want to skip any characters, but specify only a certain number
of characters to extract, you can use the syntax %myvar:~0,x
where you specify that zero characters are to be skipped and x
represents the number of characters to extract from the string.
C:\>echo %userprofile:~0,3% C:\
You can also specify that you want to start the extraction from the end of
the line rather than the beginning by using -x, where
x is some number, for the starting position. E.g. you could
use the following to extract the last 3 characters from the line:
C:\>echo %userprofile:~-3% mes
You can specify the number of characters to extract, just as noted before, with this method as well. E.g. to extract the substring that starts at 3 characters from the end of the string, but only includes 2 characters from that point, the following could be used:
C:\>echo %userprofile:~-3,2% me
If you are using a batch file, e.g. substring-extract-example.bat,
you could display just the desired part of the string as follows:
@echo off
echo %userprofile:~-3,2%
When the batch file is executed, it wold display just "me"
C:\>substr-extract-example me
For further examples, see Variables: extract part of a variable (substring)
References:
