sqs2poscarcpp In function ‘int mainint char’sqs2poscarcpp22213 error ‘strcat’ was not declared in this scope 222 osopenstrcatfile -POSCAR; ^~~~~~sqs2poscarcpp191 note ‘strcat’

This error message is indicating that the function strcat is not declared in the current scope. The suggested solution is to include the header file <cstring> which contains the declaration for strcat.

To fix this error, add the line #include <cstring> to the top of the file, above all other include statements.