It is possible to retrieve specific characters from a string variable.
Syntax %variable:~num_chars_to_skip% %variable:~num_chars_to_skip,num_chars_to_keep% This can include negative numbers: %variable:~num_chars_to_skip, -num_chars_to_keep% %variable:~-num_chars_to_skip,num_chars_to_keep% %variable:~-num_chars_to_skip,-num_chars_to_keep%
A negative number will count backwards from the end of the string.
The variable _test is used for all the following examples:
SET _test=123456789abcdef0 ::Extract only the first 5 characters SET _result=%_test:~0,5% ECHO %_result% =12345 ::Skip 7 characters and then extract the next 5 SET _result=%_test:~7,5% ECHO %_result% =89abc ::Skip 7 characters and then extract everything else SET _result=%_test:~7% ECHO %_result% =89abcdef0 ::Extract only the last 7 characters SET _result=%_test:~-7% ECHO %_result% =abcdef0 ::Extract everything BUT the last 7 characters SET _result=%_test:~0,-7% ECHO %_result% =123456789 ::Extract between 7 from the front and 5 from the end SET _result=%_test:~7,-5% ECHO %_result% =89ab ::Go back 7 from the end then extract 5 towards the end SET _result=%_test:~-7,5% ECHO %_result% =abcde ::Extract between 7 from the end and 5 from the end SET _result=%_test:~-7,-5% ECHO %_result% =ab
This variable substring syntax only works for CMD environment variables, like %MYVAR%, it will not work with FOR parameter variables, like %%G, however a simple workaround is to set a variable first: Set %MYVAR%=%%G and then find the substring of the new variable.
To discover if a given variable contains a given string: use the syntax above to remove the _SearchString and compare the result with the original variable before removal. If both strings are the same, then_SearchString was not found:
IF /i "%_variable:_SearchString=%"=="%_variable%" (Echo String not found.) ELSE (Echo String found.)
To match an exact word, pad the search string with spaces: " John " instead of "John" will avoid a match with "Johnstone"
Advanced Usage of :~
You can use the :~ syntax and provide each of the parameters from other variables, for example if you have
To extract digit # 4 from _donor you might try
Unfortunately this will not work because the :~ syntax expects a value not a variable. To get around this use the CALL command like this:
SET _startchar=2 SET _length=1 SET _donor=884777 CALL SET _substring=%%_donor:~%_startchar%,%_length%%% ECHO (%_substring%)
:: Clay Calvert - alt.msdos.batch.nt
:: Ritchie Lawrence - alt.msdos.batch.nt
#Substitute Me for him, Substitute My Coke for gin, Substitute You for my mum, At least I'll get my washing done# ~ The Who (Substitute)
VarSearch - Search & replace part of a variable.
strlen.cmd - Get string length.